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   Geospatial Data Carpentry for Urbanism
 </div>
 
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   Geospatial Data Carpentry for Urbanism
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@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
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diff --git a/09-open-and-plot-vector-layers.html b/09-open-and-plot-vector-layers.html
index 93aa67c8..c56a23fa 100644
--- a/09-open-and-plot-vector-layers.html
+++ b/09-open-and-plot-vector-layers.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
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+<aside class="col-md-12 lesson-progress"><div style="width: 22%" class="percentage">
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 </aside><div class="container">
@@ -360,8 +360,8 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
-<ul><li>Know the difference between point, line, and polygon vector
-data.</li>
+<p>After completing this episode, participants should be able to…</p>
+<ul><li>Differentiate between point, line, and polygon vector data.</li>
 <li>Load vector data into R.</li>
 <li>Access the attributes of a vector object in R.</li>
 </ul></div>
@@ -378,25 +378,23 @@ <h3 class="card-title">Objectives</h3>
 <h3 class="callout-title">Prerequisite<a class="anchor" aria-label="anchor" href="#prereq1"></a>
 </h3>
 <div class="callout-content">
-<p>If you have not installed the <code>sf</code> package yet, run
-<code>install.packages("sf")</code> first. Note that the <code>sf</code>
-package has some external dependencies, namely GEOS, PROJ.4, GDAL and
-UDUNITS, which need to be installed beforehand. Follow the workshop <a href="">setup instructions</a> for the installation of <code>sf</code>
-and its dependencies.</p>
+<p>In this lesson you will work with the <code>sf</code> package. Note
+that the <code>sf</code> package has some external dependencies, namely
+GEOS, PROJ.4, GDAL and UDUNITS, which need to be installed beforehand.
+Before starting the lesson, follow the workshop <a href="index.html#setup">setup instructions</a> for the installation of
+<code>sf</code> and its dependencies.</p>
 </div>
 </div>
 </div>
 <p>First we need to load the packages we will use in this lesson. We
-will use the packages <code>tidyverse</code> and <code>here</code> with
-which you are already familiar from the previous lesson. In addition, we
-need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
+will use the <code>tidyverse</code> package with which you are already
+familiar from the previous lesson. In addition, we need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
 working with spatial vector data.</p>
 <div class="codewrapper sourceCode" id="cb1">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># tools for wrangling, reshaping and visualizing data</span></span>
-<span><span class="kw">library</span><span class="op">(</span><span class="va">here</span><span class="op">)</span>       <span class="co"># managing paths</span></span>
+<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># wrangle, reshape and visualize data</span></span>
 <span><span class="kw">library</span><span class="op">(</span><span class="va">sf</span><span class="op">)</span>         <span class="co"># work with spatial vector data</span></span></code></pre>
 </div>
 <div id="the-sf-package" class="callout callout">
@@ -409,23 +407,25 @@ <h3 class="callout-title">The<code>sf</code>package<a class="anchor" aria-label=
 <div class="callout-content">
 <p><code>sf</code> stands for Simple Features which is a standard
 defined by the Open Geospatial Consortium for storing and accessing
-geospatial vector data. PostGIS uses the same standard; so those of you
-who used PostGIS, might find some resemblances with the functions used
-by the <code>sf</code> package.</p>
+geospatial vector data. PostGIS, for instance, uses the same standard,
+so PostGIS users might recognise the functions used by the
+<code>sf</code> package.</p>
 </div>
 </div>
 </div>
 <section id="import-shapefiles"><h2 class="section-heading">Import shapefiles<a class="anchor" aria-label="anchor" href="#import-shapefiles"></a>
 </h2>
-<hr class="half-width"><p>Let’s start by opening a shapefile. Shapefiles a common file format
-to store spatial vector data used in GIS software. We will read a
-shapefile with the administrative boundary of Delft with the function
+<hr class="half-width"><p>Let’s start by opening a shapefile. Shapefiles are a common file
+format to store spatial vector data used in GIS software. Note that a
+shapefile consists of multiple files and it is important to keep them
+all together in the same location. We will read a shapefile with the
+administrative boundary of Delft with the function
 <code>st_read()</code> from the <code>sf</code> package.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span>, quiet <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="all-sf-functions-start-with-st_" class="callout callout">
 <div class="callout-square">
@@ -437,21 +437,24 @@ <h3 class="callout-title">All<code>sf</code>functions start with<code>st_</code>
 <div class="callout-content">
 <p>Note that all functions from the <code>sf</code> package start with
 the standard prefix <code>st_</code> which stands for Spatial Type. This
-is helpful in at least two ways: (1) it makes the interaction with or
-translation to/from software using the simple features standard like
-PostGIS easy, and (2) it allows for easy autocompletion of function
-names in RStudio.</p>
-</div>
+is helpful in at least two ways:</p>
+<ol style="list-style-type: decimal"><li>it allows for easy autocompletion of function names in RStudio,
+and</li>
+<li>it makes the interaction with or translation to/from software using
+the simple features standard like PostGIS easy.</li>
+</ol></div>
 </div>
 </div>
 </section><section id="spatial-metadata"><h2 class="section-heading">Spatial Metadata<a class="anchor" aria-label="anchor" href="#spatial-metadata"></a>
 </h2>
-<hr class="half-width"><p>The <code>st_read()</code> function gave us a message with a summary
-of metadata about the file that was read in. To examine the metadata in
+<hr class="half-width"><p>By default (with <code>quiet = FALSE</code>), the
+<code>st_read()</code> function provides a message with a summary of
+metadata about the file that was read in. To examine the metadata in
 more detail, we can use other, more specialised, functions from the
-<code>sf</code> package. The <code>st_geometry_type()</code> function,
-for instance, gives us information about the geometry type, which in
-this case is <code>POLYGON</code>.</p>
+<code>sf</code> package.</p>
+<p>The <code>st_geometry_type()</code> function, for instance, gives us
+information about the geometry type, which in this case is
+<code>POLYGON</code>.</p>
 <div class="codewrapper sourceCode" id="cb3">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -466,7 +469,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </div>
 <p>The <code>st_crs()</code> function returns the coordinate reference
 system (CRS) used by the shapefile, which in this case is
-<code>WGS84</code> and has the unique reference code
+<code>WGS 84</code> and has the unique reference code
 <code>EPSG: 4326</code>.</p>
 <div class="codewrapper sourceCode" id="cb5">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -510,7 +513,7 @@ <h3 class="callout-title">Examining the output of<code>st_crs()</code><a class="
 </div>
 </div>
 <p>The <code>st_bbox()</code> function shows the extent of the layer. As
-<code>WGS84</code> is a <strong>geographic CRS</strong>, the extent of
+<code>WGS 84</code> is a <strong>geographic CRS</strong>, the extent of
 the shapefile is displayed in degrees.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -529,62 +532,34 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 our shapefile, we will use the <code>st_transform()</code> function. For
 the <code>crs</code> argument we can use the EPSG code of the CRS we
 want to use, which is <code>28992</code> for the
-<code>Amersfort / RD New</code> projection.</p>
+<code>Amersfort / RD New</code> projection. To check the EPSG code of
+any CRS, we can check this website: <a href="https://epsg.io/" class="external-link uri">https://epsg.io/</a></p>
 <div class="codewrapper sourceCode" id="cb9">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_transform</span><span class="op">(</span><span class="va">boundary_Delft</span>, <span class="fl">28992</span><span class="op">)</span></span>
-<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span></span></code></pre>
+<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">Name</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>Coordinate Reference System:
-  User input: EPSG:28992 
-  wkt:
-PROJCRS["Amersfoort / RD New",
-    BASEGEOGCRS["Amersfoort",
-        DATUM["Amersfoort",
-            ELLIPSOID["Bessel 1841",6377397.155,299.1528128,
-                LENGTHUNIT["metre",1]]],
-        PRIMEM["Greenwich",0,
-            ANGLEUNIT["degree",0.0174532925199433]],
-        ID["EPSG",4289]],
-    CONVERSION["RD New",
-        METHOD["Oblique Stereographic",
-            ID["EPSG",9809]],
-        PARAMETER["Latitude of natural origin",52.1561605555556,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8801]],
-        PARAMETER["Longitude of natural origin",5.38763888888889,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8802]],
-        PARAMETER["Scale factor at natural origin",0.9999079,
-            SCALEUNIT["unity",1],
-            ID["EPSG",8805]],
-        PARAMETER["False easting",155000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8806]],
-        PARAMETER["False northing",463000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8807]]],
-    CS[Cartesian,2],
-        AXIS["easting (X)",east,
-            ORDER[1],
-            LENGTHUNIT["metre",1]],
-        AXIS["northing (Y)",north,
-            ORDER[2],
-            LENGTHUNIT["metre",1]],
-    USAGE[
-        SCOPE["Engineering survey, topographic mapping."],
-        AREA["Netherlands - onshore, including Waddenzee, Dutch Wadden Islands and 12-mile offshore coastal zone."],
-        BBOX[50.75,3.2,53.7,7.22]],
-    ID["EPSG",28992]]</code></pre>
+<pre class="output" tabindex="0"><code>[1] "Amersfoort / RD New"</code></pre>
+</div>
+<div class="codewrapper sourceCode" id="cb11">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
 <p>Notice that the bounding box is measured in meters after the
 transformation.</p>
-<div class="codewrapper sourceCode" id="cb11">
+<div class="codewrapper sourceCode" id="cb13">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -596,9 +571,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81743.00 442446.21  87703.78 449847.95 </code></pre>
 </div>
+<div class="codewrapper sourceCode" id="cb15">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">units_gdal</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] "metre"</code></pre>
+</div>
 <p>We confirm the transformation by examining the reprojected
 shapefile.</p>
-<div class="codewrapper sourceCode" id="cb13">
+<div class="codewrapper sourceCode" id="cb17">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -623,19 +609,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#callout4"></a>
 </h3>
 <div class="callout-content">
-<p>More about CRS in <a href="">Handling Spatial Projection &amp;
-CRS</a>.</p>
+<p>Read more about Coordinate Reference Systems <a href="https://datacarpentry.org/organization-geospatial/03-crs.html" class="external-link">here</a>.
+We will also practice transformation between CRS in <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial
+Projection &amp; CRS</a>.</p>
 </div>
 </div>
 </div>
 </section><section id="plot-a-vector-layer"><h2 class="section-heading">Plot a vector layer<a class="anchor" aria-label="anchor" href="#plot-a-vector-layer"></a>
 </h2>
 <hr class="half-width"><p>Now, let’s plot this shapefile. You are already familiar with the
-<code>ggplot2</code> package from <a href="">Introduction to
-Visualisation</a>. <code>ggplot2</code> has special <code>geom_</code>
-functions for spatial data. We will use the <code>geom_sf()</code>
-function for <code>sf</code> data.</p>
-<div class="codewrapper sourceCode" id="cb15">
+<code>ggplot2</code> package from <a href="04-intro-to-visualisation.html">Introduction to Visualisation</a>.
+<code>ggplot2</code> has special <code>geom_</code> functions for
+spatial data. We will use the <code>geom_sf()</code> function for
+<code>sf</code> data.</p>
+<div class="codewrapper sourceCode" id="cb19">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -644,18 +631,18 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Delft Administrative Boundary"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span>  <span class="co"># this is needed to display the axes in meters</span></span></code></pre>
 </div>
-<figure><img src="fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-1-import-line-and-point-vector-layers" class="callout challenge">
+<figure><img src="fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-import-line-and-point-vector-layers" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="challenge-1-import-line-and-point-vector-layers" class="callout-inner">
-<h3 class="callout-title">Challenge 1: Import line and point vector
-layers<a class="anchor" aria-label="anchor" href="#challenge-1-import-line-and-point-vector-layers"></a>
+<div id="challenge-import-line-and-point-vector-layers" class="callout-inner">
+<h3 class="callout-title">Challenge: Import line and point vector
+layers<a class="anchor" aria-label="anchor" href="#challenge-import-line-and-point-vector-layers"></a>
 </h3>
 <div class="callout-content">
 <p>Read in <code>delft-streets.shp</code> and
 <code>delft-leisure.shp</code> and assign them to
-<code>lines_Delft</code> and <code>point_Delft</code> respectively.
+<code>lines_Delft</code> and <code>points_Delft</code> respectively.
 Answer the following questions:</p>
 <ol style="list-style-type: decimal"><li>What type of R spatial object is created when you import each
 layer?</li>
@@ -670,44 +657,47 @@ <h3 class="callout-title">Challenge 1: Import line and point vector
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
-<div class="codewrapper sourceCode" id="cb16">
+<div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">lines_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-streets.shp"</span><span class="op">)</span></span>
-<span><span class="va">point_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
+<span><span class="va">points_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
 </div>
-<p>We can check the type of data with the <code>class()</code> function
-from base R. Both <code>lines_Delft</code> and <code>point_Delft</code>
-are objects of class <code>"sf"</code>, which extends the
-<code>"data.frame"</code> class.</p>
-<div class="codewrapper sourceCode" id="cb17">
+<p>We can check the type of type of geometry with the
+<code>st_geometry_type()</code> function. <code>lines_Delft</code>
+contains <code>"LINESTRING"</code> geometry and
+<code>points_Delft</code> is made of <code>"POINT"</code>
+geometries.</p>
+<div class="codewrapper sourceCode" id="cb21">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">1</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] LINESTRING
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb19">
+<div class="codewrapper sourceCode" id="cb23">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">2</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] POINT
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<p><code>lines_Delft</code> and <code>point_Delft</code> are in the
+<p><code>lines_Delft</code> and <code>points_Delft</code> are in the
 correct CRS.</p>
-<div class="codewrapper sourceCode" id="cb21">
+<div class="codewrapper sourceCode" id="cb25">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -718,11 +708,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb23">
+<div class="codewrapper sourceCode" id="cb27">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -732,8 +722,8 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <p>When looking at the bounding boxes with the <code>st_bbox()</code>
 function, we see the spatial extent of the two objects in a projected
 CRS using meters as units. <code>lines_Delft()</code> and
-<code>point_Delft</code> have similar extents.</p>
-<div class="codewrapper sourceCode" id="cb25">
+<code>points_Delft</code> have similar extents.</p>
+<div class="codewrapper sourceCode" id="cb29">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -745,11 +735,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81759.58 441223.13  89081.41 449845.81 </code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb27">
+<div class="codewrapper sourceCode" id="cb31">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -773,7 +763,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul></div>
diff --git a/10-explore-and-plot-by-vector-layer-attributes.html b/10-explore-and-plot-by-vector-layer-attributes.html
index 364ad262..6a04ed3c 100644
--- a/10-explore-and-plot-by-vector-layer-attributes.html
+++ b/10-explore-and-plot-by-vector-layer-attributes.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 28%" class="percentage">
-    28%
+<aside class="col-md-12 lesson-progress"><div style="width: 30%" class="percentage">
+    30%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 28%" aria-valuenow="28" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 30%" aria-valuenow="30" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -350,6 +350,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li><p>Query attributes of a vector object.</p></li>
 <li><p>Subset vector objects using specific attribute values.</p></li>
 <li><p>Plot a vector feature, colored by unique attribute
@@ -437,13 +438,13 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </div>
 </div>
 <p>We can also preview the content of the object by looking at the first
-6 rows with the <code>head()</code> function, which is in the case of an
-<code>sf</code> object the same as examining the object directly.</p>
+6 rows with the <code>head()</code> function, which in the case of an
+<code>sf</code> object is similar to examining the object directly.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span> <span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -529,6 +530,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 [21] "tertiary"       "tertiary_link"  "track"          "trunk"         
 [25] "trunk_link"     "unclassified"  </code></pre>
 </div>
+<p>Note that this way the values are shown by default in alphabetical
+order and <code>NA</code>s are not displayed, whereas using
+<code>unique()</code> returns unique values in the order of their
+occurrence in the data frame and it also shows <code>NA</code>
+values.</p>
 </div>
 </div>
 </div>
@@ -635,7 +641,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="co"># point_Delft</span></span></code></pre>
 </div>
-<p>However, this is not a good approach as the first rows might still
+<p>We have our answer (<code>sports_centre</code> is the third value),
+but in general this is not a good approach as the first rows might still
 have many <code>NA</code>s and three distinct values might still not be
 present in the first <code>n</code> rows of the data frame. To remove
 <code>NA</code>s, we can use the function <code>na.omit()</code> on the
@@ -654,19 +661,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] "picnic_table"  "marina"        "marina"        "sports_centre"
 [5] "sports_centre" "playground"   </code></pre>
 </div>
-<p>To show only unique values, we can use the <code>unique()</code>
-function to only see the first occurrence of each distinct value (note
-that <code>NA</code> will still be included once).</p>
+<p>To show only unique values, we can use the <code>levels()</code>
+function on a factor to only see the first occurrence of each distinct
+value. Note <code>NA</code>s are dropped in this case and that we get
+the first three of the unique alphabetically ordered values.</p>
 <div class="codewrapper sourceCode" id="cb24">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">unique</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">levels</span><span class="op">(</span><span class="fu">factor</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "picnic_table" "marina"       NA            </code></pre>
+<pre class="output" tabindex="0"><code>[1] "dance"       "dog_park"    "escape_game"</code></pre>
 </div>
 <ol start="3" style="list-style-type: decimal"><li>To see a list of all attribute names, we can use the
 <code>names()</code> function.</li>
@@ -766,6 +774,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 </h3>
 <div class="callout-content">
 <!-- 7 minutes -->
+<p>Challenge: Now with motorways (and pedestrian streets)</p>
 <ol style="list-style-type: decimal"><li>Create a new object that only contains the motorways in Delft.</li>
 <li>How many features does the new object have?</li>
 <li>What is the total length of motorways?</li>
@@ -855,7 +864,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 48</code></pre>
 </div>
-<ol start="4" style="list-style-type: decimal"><li>Plot the motorways</li>
+<ol start="4" style="list-style-type: decimal"><li>Plot the motorways.</li>
 </ol><div class="codewrapper sourceCode" id="cb43">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -865,7 +874,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Fast mobility network"</span>, subtitle <span class="op">=</span> <span class="st">"Motorways"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal"><li>Same steps with pedestrian streets</li>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal"><li>Follow the same steps with pedestrian streets.</li>
 </ol><div class="codewrapper sourceCode" id="cb44">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -941,8 +950,10 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 expression in which we only filter the rows of our data frame that have
 one of the four given values <code>"motorway"</code>,
 <code>"primary"</code>, <code>"secondary"</code>, and
-<code>"cycleway"</code>. We also make sure that the highway column is a
-factor column.</p>
+<code>"cycleway"</code>. Note that we do this with the <code>%in</code>
+operator which is a more compact equivalent of a series of conditions
+joined by the <code>|</code> (or) operator. We also make sure that the
+highway column is a factor column.</p>
 <div class="codewrapper sourceCode" id="cb51">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -956,7 +967,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <p>Next we define the four colors we want to use, one for each type of
 road in our vector object. Note that in R you can use named colors like
 <code>"blue"</code>, <code>"green"</code>, <code>"navy"</code>, and
-<code>"purple"</code>. A full list of named colors can be listed with
+<code>"purple"</code>. If you are using RStudio, you will see the named
+colors previewed in line. A full list of named colors can be listed with
 the <code>colors()</code> function.</p>
 <div class="codewrapper sourceCode" id="cb52">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1006,12 +1018,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">scale_linewidth_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">line_widths</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-line-width-by-attribute" class="callout challenge">
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-line-width-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-line-width-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot line width by attribute<a class="anchor" aria-label="anchor" href="#plot-line-width-by-attribute"></a>
+<div id="challenge-plot-line-width-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot line width by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-line-width-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <p>In the example above, we set the line widths to be 1, 0.75, 0.5, and
@@ -1077,13 +1089,14 @@ <h2 id="add-plot-legend">Add plot legend<a class="anchor" aria-label="anchor" hr
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
+<code class="sourceCode R"><span><span class="va">p1</span> <span class="op">&lt;-</span> <span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
 <span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Default Legend"</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span>
+<span><span class="va">p1</span></span></code></pre>
 </div>
 <figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-34-1.png" alt="Mobility network in Delft using thicker lines than the previous example." class="figure mx-auto d-block"><figcaption>
 Mobility network in Delft using thicker lines than the previous example.
@@ -1091,15 +1104,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
+<code class="sourceCode R"><span><span class="va">p2</span> <span class="op">&lt;-</span> <span class="va">p1</span> <span class="op">+</span></span>
 <span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1110,33 +1117,21 @@ <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left">
 Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
 generated.</code></pre>
 </div>
-<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft with large-font and border around
-the legend.
-</figcaption></figure><div class="codewrapper sourceCode" id="cb63">
+<div class="codewrapper sourceCode" id="cb63">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">new_colors</span> <span class="op">&lt;-</span> <span class="fu">c</span><span class="op">(</span><span class="st">"springgreen"</span>, <span class="st">"blue"</span>, <span class="st">"magenta"</span>, <span class="st">"orange"</span><span class="op">)</span></span>
-<span></span>
-<span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">new_colors</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">p2</span></span></code></pre>
 </div>
-<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><div id="plot-lines-by-attributes" class="callout challenge">
+<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
+Map of the mobility network in Delft with large-font and border around
+the legend.
+</figcaption></figure><div id="challenge-plot-lines-by-attributes" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-lines-by-attributes" class="callout-inner">
-<h3 class="callout-title">Plot lines by attributes<a class="anchor" aria-label="anchor" href="#plot-lines-by-attributes"></a>
+<div id="challenge-plot-lines-by-attributes" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot lines by attributes<a class="anchor" aria-label="anchor" href="#challenge-plot-lines-by-attributes"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -1200,16 +1195,16 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network in Delft"</span>, subtitle <span class="op">=</span> <span class="st">"Roads dedicated to Bikes"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
 </div>
 </div>
 </div>
-<div id="plot-polygon-by-attribute" class="callout challenge">
+<div id="challenge-plot-polygon-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-polygon-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#plot-polygon-by-attribute"></a>
+<div id="challenge-plot-polygon-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-polygon-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -1230,7 +1225,7 @@ <h4 class="accordion-header" id="headingSolution5">Show me the solution</h4>
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="fu">here</span><span class="op">(</span><span class="st">"data"</span>, <span class="st">"nl-gemeenten.shp"</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/nl-gemeenten.shp"</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1290,7 +1285,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
 </div>
 </div>
 </div>
diff --git a/11-plot-multiple-shape-files.html b/11-plot-multiple-shape-files.html
index cd23c437..33166615 100644
--- a/11-plot-multiple-shape-files.html
+++ b/11-plot-multiple-shape-files.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 35%" class="percentage">
-    35%
+<aside class="col-md-12 lesson-progress"><div style="width: 43%" class="percentage">
+    43%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 35%" aria-valuenow="35" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 43%" aria-valuenow="43" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -359,6 +359,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li>Plot multiple vector layers in the same plot.</li>
 <li>Apply custom symbols to spatial objects in a plot.</li>
 </ul></div>
@@ -366,17 +367,16 @@ <h3 class="card-title">Objectives</h3>
 </div>
 </div>
 </div>
-<p>This episode builds upon the <a href="">previous episode</a> to work
-with vector layers in R and explore how to plot multiple vector
-layers.</p>
+<p>This episode builds upon the <a href="10-explore-and-plot-by-vector-layer-attributes.html">previous
+episode</a> to work with vector layers in R and explore how to plot
+multiple vector layers.</p>
 <section id="load-the-data"><h2 class="section-heading">Load the data<a class="anchor" aria-label="anchor" href="#load-the-data"></a>
 </h2>
-<hr class="half-width"><p>To work with vector data in R, we can use the <code>sf</code>
-library. The <code>terra</code> package also allows us to explore
-metadata using similar commands for both raster and vector files. Make
-sure that you have these packages loaded.</p>
+<hr class="half-width"><p>To work with vector data in R, we use the <code>sf</code> library.
+Make sure that it is loaded.</p>
 <p>We will continue to work with the three ESRI shapefiles that we
-loaded in the <a href="">Open and Plot Vector Layers</a> episode.</p>
+loaded in the <a href="09-open-and-plot-vector-layers.html">Open and
+Plot Vector Layers</a> episode.</p>
 </section><section id="plotting-multiple-vector-layers"><h2 class="section-heading">Plotting Multiple Vector Layers<a class="anchor" aria-label="anchor" href="#plotting-multiple-vector-layers"></a>
 </h2>
 <hr class="half-width"><p>So far we learned how to plot information from a single shapefile and
@@ -401,14 +401,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the symbology (the colors and
-symbols) that we used to create the plot above. For example, it might be
-good if the lines were symbolized as lines. In the previous episode, you
-may have noticed that the default legend behavior for
-<code>geom_sf</code> is to draw a ‘patch’ for each legend entry. If you
-want the legend to draw lines or points, you need to add an instruction
-to the <code>geom_sf</code> call - in this case,
-<code>show.legend = 'line'</code>.</p>
+<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the functions
+<code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code>.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -440,8 +435,15 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-3-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>We notice that there are quite some playgrounds in the residential
 parts of Delft, whereas on campus there is a concentration of picnic
 tables. So that is what our next challenge is about.</p>
-<div class="section level3">
-<h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-label="anchor" href="#challenge-7-5-minutes"></a></h3>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout challenge">
+<div class="callout-square">
+<i class="callout-icon" data-feather="zap"></i>
+</div>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout-inner">
+<h3 class="callout-title">Challenge: Visualising multiple layers with a
+custom legend<a class="anchor" aria-label="anchor" href="#challenge-visualising-multiple-layers-with-a-custom-legend"></a>
+</h3>
+<div class="callout-content">
 <p>Create a map of leisure locations only including
 <code>playground</code> and <code>picnic_table</code>, with each point
 colored by the leisure type. Overlay this layer on top of the
@@ -449,6 +451,16 @@ <h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-lab
 that applies line symbols to lines and point symbols to the points.</p>
 <p>Modify the plot above. Tell R to plot each point, using a different
 symbol of shape value.</p>
+</div>
+</div>
+</div>
+<div id="accordionSolution1" class="accordion challenge-accordion accordion-flush">
+<div class="accordion-item">
+<button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
+  <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
+</button>
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb4">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -492,7 +504,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span>, <span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">leisure_locations_selection</span>, <span class="fu">aes</span><span class="op">(</span>fill <span class="op">=</span> <span class="va">leisure</span><span class="op">)</span>, </span>
-<span>          shape <span class="op">=</span> <span class="fl">21</span>, show.legend <span class="op">=</span> <span class="st">'point'</span><span class="op">)</span> <span class="op">+</span> </span>
+<span>          shape <span class="op">=</span> <span class="fl">21</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Line Type"</span>, values <span class="op">=</span> <span class="va">road_colors</span>,</span>
 <span>     guide <span class="op">=</span> <span class="fu">guide_legend</span><span class="op">(</span>override.aes <span class="op">=</span> <span class="fu">list</span><span class="op">(</span>linetype <span class="op">=</span> <span class="st">"solid"</span>, shape <span class="op">=</span> <span class="cn">NA</span><span class="op">)</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_fill_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Soil Type"</span>, values <span class="op">=</span> <span class="va">blue_orange</span>,</span>
@@ -515,7 +527,11 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Road network and leisure"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><!-- End of challenge --><div id="keypoints1" class="callout keypoints">
+<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+</div>
+</div>
+</div>
+<div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
 <i class="callout-icon" data-feather="key"></i>
 </div>
@@ -526,10 +542,8 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <ul><li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul></div>
 </div>
 </div>
@@ -537,7 +551,6 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 Place links that you need to refer to multiple times across pages here. Delete
 any links that you are not going to use. 
  -->
-</div>
 </section></div> <!-- / div.lesson-content -->
     </main><!-- / main#main-content.main-content --><nav class="bottom-pagination mx-md-4" aria-label="Previous and Next Chapter"><div class="d-block d-sm-block d-md-none">
         <a class="chapter-link" href="10-explore-and-plot-by-vector-layer-attributes.html"><i aria-hidden="true" class="small-arrow" data-feather="arrow-left"></i>Previous</a>
diff --git a/12-handling-spatial-projection-and-crs.html b/12-handling-spatial-projection-and-crs.html
index d7cc1c8e..fcd560d0 100644
--- a/12-handling-spatial-projection-and-crs.html
+++ b/12-handling-spatial-projection-and-crs.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 49%" class="percentage">
-    49%
+<aside class="col-md-12 lesson-progress"><div style="width: 52%" class="percentage">
+    52%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 49%" aria-valuenow="49" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 52%" aria-valuenow="52" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -358,6 +358,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li>Plot vector objects with different CRSs in the same plot.</li>
 </ul></div>
 </div>
@@ -498,18 +499,20 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Map of Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-multiple-layers-of-spatial-data" class="callout challenge">
+<figure><img src="fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-multiple-layers-of-spatial-data" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-multiple-layers-of-spatial-data" class="callout-inner">
-<h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor" aria-label="anchor" href="#plot-multiple-layers-of-spatial-data"></a>
+<div id="challenge-plot-multiple-layers-of-spatial-data" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot multiple layers of spatial
+data<a class="anchor" aria-label="anchor" href="#challenge-plot-multiple-layers-of-spatial-data"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
 <p>Create a map of South Holland as follows:</p>
-<ol style="list-style-type: decimal"><li>Import and plot <code>nl-gemeenten.shp</code>. Adjust line width as
-necessary.</li>
+<ol style="list-style-type: decimal"><li>Import <code>nl-gemeenten.shp</code> and filter only the
+municipalities in South Holland.</li>
+<li>Plot it and adjust line width as necessary.</li>
 <li>Layer the boundary of Delft onto the plot.</li>
 <li>Add a title.</li>
 <li>Add a legend that shows both the province boundaries (as a line) and
@@ -522,7 +525,7 @@ <h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb18">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -551,12 +554,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 </section><section id="export-a-shapefile"><h2 class="section-heading">Export a shapefile<a class="anchor" aria-label="anchor" href="#export-a-shapefile"></a>
 </h2>
 <hr class="half-width"><p>To save a file, use the <code>st_write()</code> function from the
-<code>sf</code> package.</p>
+<code>sf</code> package. Although <code>sf</code> guesses the driver
+needed for a specified output file name from its extension, this can be
+made explicitly via the <code>driver</code> argument. In our case
+<code>driver = "ESRI Shapefile"</code> ensures that the output is
+correctly saved as a <code>.shp</code> file.</p>
 <div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="sourceCode r" tabindex="0"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true" tabindex="-1"></a><span class="fu">st_write</span>(leisure_locations_selection,</span>
-<span id="cb20-2"><a href="#cb20-2" aria-hidden="true" tabindex="-1"></a>         <span class="st">"data/leisure_locations_selection.shp"</span>), driver <span class="ot">=</span> <span class="st">"ESRI Shapefile"</span><span class="er">)</span></span></code></pre>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_write</span><span class="op">(</span><span class="va">leisure_locations_selection</span>,</span>
+<span>         <span class="st">"data/leisure_locations_selection.shp"</span>, driver <span class="op">=</span> <span class="st">"ESRI Shapefile"</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
diff --git a/13-intro-to-raster-data.html b/13-intro-to-raster-data.html
index a0bb590e..4280e358 100644
--- a/13-intro-to-raster-data.html
+++ b/13-intro-to-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 63%" class="percentage">
-    63%
+<aside class="col-md-12 lesson-progress"><div style="width: 60%" class="percentage">
+    60%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 63%" aria-valuenow="63" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 60%" aria-valuenow="60" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -710,7 +710,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <p><code>+units=m</code> in the output of the code above tells us that
 our data is in meters (m).</p>
@@ -893,7 +893,7 @@ <h3 class="callout-title">Challenge: Explore raster metadata<a class="anchor" ar
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">Show me the solution</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb30">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/14-plot-raster-data.html b/14-plot-raster-data.html
index 85497f2f..0d367b60 100644
--- a/14-plot-raster-data.html
+++ b/14-plot-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 71%" class="percentage">
-    71%
+<aside class="col-md-12 lesson-progress"><div style="width: 68%" class="percentage">
+    68%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 71%" aria-valuenow="71" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 68%" aria-valuenow="68" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/15-reproject-raster-data.html b/15-reproject-raster-data.html
index 5c6c3a9a..a6702193 100644
--- a/15-reproject-raster-data.html
+++ b/15-reproject-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 79%" class="percentage">
-    79%
+<aside class="col-md-12 lesson-progress"><div style="width: 77%" class="percentage">
+    77%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 79%" aria-valuenow="79" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 77%" aria-valuenow="77" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/16-raster-calculations.html b/16-raster-calculations.html
index 7c51ea6a..ede062e9 100644
--- a/16-raster-calculations.html
+++ b/16-raster-calculations.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 87%" class="percentage">
-    87%
+<aside class="col-md-12 lesson-progress"><div style="width: 86%" class="percentage">
+    86%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 87%" aria-valuenow="87" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 86%" aria-valuenow="86" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -625,7 +625,7 @@ <h3 class="callout-title">Challenge: Explore CHM Raster Values<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb10">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/2-vector-slides.html b/2-vector-slides.html
new file mode 100644
index 00000000..076caf95
--- /dev/null
+++ b/2-vector-slides.html
@@ -0,0 +1,1115 @@
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+  <meta name="author" content="Ana Petrović">
+  <meta name="author" content="Claudiu Forgaci">
+  <title>Intro to Geospatial Vector Data with R</title>
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+
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+
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+</head>
+<body class="quarto-light">
+  <div class="reveal">
+    <div class="slides">
+
+<section id="title-slide" class="quarto-title-block center">
+  <h1 class="title">Intro to Geospatial Vector Data with R</h1>
+
+<div class="quarto-title-authors">
+<div class="quarto-title-author">
+<div class="quarto-title-author-name">
+Ana Petrović 
+</div>
+</div>
+<div class="quarto-title-author">
+<div class="quarto-title-author-name">
+Claudiu Forgaci 
+</div>
+</div>
+</div>
+
+</section>
+<section id="intro-to-geospatial-concepts" class="title-slide slide level1 center">
+<h1>Intro to Geospatial Concepts</h1>
+
+</section>
+
+<section>
+<section id="geospatial-vector-data-in-r" class="title-slide slide level1 center">
+<h1>Geospatial Vector Data in R</h1>
+
+</section>
+<section id="the-sf-package" class="slide level2">
+<h2>The <code>sf</code> package</h2>
+
+<img data-src="https://user-images.githubusercontent.com/520851/50280460-e35c1880-044c-11e9-9ed7-cc46754e49db.jpg" class="r-stretch quarto-figure-center"></section>
+<section id="the-sf-package-1" class="slide level2">
+<h2>The <code>sf</code> package</h2>
+<ul>
+<li class="fragment"><code>sf</code> provides <a href="https://en.wikipedia.org/wiki/Simple_Features">simple features access</a> to R</li>
+<li class="fragment">represents simple features as records in a data frame with a <code>geometry</code> column</li>
+<li class="fragment">function names start with a prefix <code>st_</code> (“st” stands for spatial type), which is also handy for auto-completion in RStudio</li>
+</ul>
+</section></section>
+<section>
+<section id="open-and-plot-shapefiles" class="title-slide slide level1 center">
+<h1>Open and Plot Shapefiles</h1>
+
+</section>
+<section id="challenge-1-5-mins" class="slide level2">
+<h2>Challenge 1: 🕟 <strong>5 mins</strong></h2>
+<p>Read in <code>delft-streets.shp</code> and <code>delft-leisure.shp</code> and call them <code>lines_Delft</code> and <code>point_Delft</code> respectively.</p>
+<p>Answer the following questions:</p>
+<ol type="1">
+<li class="fragment">What type of R spatial object is created when you import each layer?</li>
+<li class="fragment">What is the CRS and extent for each object?</li>
+<li class="fragment">Do the files contain points, lines, or polygons?</li>
+<li class="fragment">How many spatial objects are in each file?</li>
+</ol>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_f9a27f10" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">03</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb1"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb1-1"><a href="#cb1-1"></a>lines_Delft <span class="ot">&lt;-</span> <span class="fu">st_read</span>(<span class="fu">here</span>(<span class="st">"episodes"</span>, <span class="st">"data"</span>, <span class="st">"delft-streets.shp"</span>))</span>
+<span id="cb1-2"><a href="#cb1-2"></a>point_Delft <span class="ot">&lt;-</span> <span class="fu">st_read</span>(<span class="fu">here</span>(<span class="st">"episodes"</span>, <span class="st">"data"</span>, <span class="st">"delft-leisure.shp"</span>))</span>
+<span id="cb1-3"><a href="#cb1-3"></a></span>
+<span id="cb1-4"><a href="#cb1-4"></a><span class="fu">st_geometry_type</span>(lines_Delft)</span>
+<span id="cb1-5"><a href="#cb1-5"></a><span class="fu">st_geometry_type</span>(point_Delft)</span>
+<span id="cb1-6"><a href="#cb1-6"></a></span>
+<span id="cb1-7"><a href="#cb1-7"></a><span class="fu">st_crs</span>(lines_Delft)</span>
+<span id="cb1-8"><a href="#cb1-8"></a><span class="fu">st_crs</span>(point_Delft)</span>
+<span id="cb1-9"><a href="#cb1-9"></a></span>
+<span id="cb1-10"><a href="#cb1-10"></a><span class="fu">st_bbox</span>(lines_Delft)</span>
+<span id="cb1-11"><a href="#cb1-11"></a><span class="fu">st_bbox</span>(point_Delft)</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section></section>
+<section>
+<section id="explore-and-plot-by-vector-layer-attributes" class="title-slide slide level1 center">
+<h1>Explore and plot by vector layer attributes</h1>
+
+</section>
+<section id="challenge-2-3-mins" class="slide level2">
+<h2>Challenge 2: 🕐 <strong>3 mins</strong></h2>
+<p>Explore the attributes associated with the <code>point_Delft</code> and <code>boundary_Delft</code> spatial objects.</p>
+<ol type="1">
+<li class="fragment">How many attributes does each have?</li>
+<li class="fragment">What types of leisure points do the points represent? Give three examples.</li>
+<li class="fragment">Which of the following is NOT an attribute of the point_Delft data object?</li>
+</ol>
+<div class="fragment">
+<p>⁣&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A) location B) leisure C) osm_id</p>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_0e0714de" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">03</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<!-- **Hint:**  -->
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb2"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb2-1"><a href="#cb2-1"></a><span class="fu">ncol</span>(point_Delft)</span>
+<span id="cb2-2"><a href="#cb2-2"></a><span class="fu">ncol</span>(boundary_Delft)</span>
+<span id="cb2-3"><a href="#cb2-3"></a></span>
+<span id="cb2-4"><a href="#cb2-4"></a><span class="fu">head</span>(point_Delft)</span>
+<span id="cb2-5"><a href="#cb2-5"></a><span class="fu">head</span>(point_Delft, <span class="dv">10</span>)</span>
+<span id="cb2-6"><a href="#cb2-6"></a></span>
+<span id="cb2-7"><a href="#cb2-7"></a>point_Delft</span>
+<span id="cb2-8"><a href="#cb2-8"></a></span>
+<span id="cb2-9"><a href="#cb2-9"></a><span class="fu">names</span>(point_Delft)</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section>
+<section id="challenge-3-5-mins" class="slide level2">
+<h2>Challenge 3: 🕢 <strong>5 mins</strong></h2>
+<ol type="1">
+<li class="fragment">Create a new object that only contains the motorways in Delft.</li>
+<li class="fragment">How many features does the new object have?</li>
+<li class="fragment">What is the total length of motorways?</li>
+<li class="fragment">Plot the motorways.</li>
+<li class="fragment">Extra: follow the same steps with pedestrian streets.</li>
+</ol>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_504b7a26" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb3"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb3-1"><a href="#cb3-1"></a><span class="fu">levels</span>(<span class="fu">factor</span>(lines_Delft<span class="sc">$</span>highway))</span>
+<span id="cb3-2"><a href="#cb3-2"></a></span>
+<span id="cb3-3"><a href="#cb3-3"></a>motorway_Delft <span class="ot">&lt;-</span> lines_Delft <span class="sc">%&gt;%</span> </span>
+<span id="cb3-4"><a href="#cb3-4"></a>  <span class="fu">filter</span>(highway <span class="sc">==</span> <span class="st">"motorway"</span>)</span>
+<span id="cb3-5"><a href="#cb3-5"></a></span>
+<span id="cb3-6"><a href="#cb3-6"></a>motorway_Delft <span class="sc">%&gt;%</span> </span>
+<span id="cb3-7"><a href="#cb3-7"></a>  <span class="fu">mutate</span>(<span class="at">length =</span> <span class="fu">st_length</span>(.)) <span class="sc">%&gt;%</span> </span>
+<span id="cb3-8"><a href="#cb3-8"></a>  <span class="fu">select</span>(<span class="fu">everything</span>(), geometry) <span class="sc">%&gt;%</span></span>
+<span id="cb3-9"><a href="#cb3-9"></a>  <span class="fu">summarise</span>(<span class="at">total_length =</span> <span class="fu">sum</span>(length))</span>
+<span id="cb3-10"><a href="#cb3-10"></a></span>
+<span id="cb3-11"><a href="#cb3-11"></a><span class="fu">nrow</span>(motorway_Delft)</span>
+<span id="cb3-12"><a href="#cb3-12"></a></span>
+<span id="cb3-13"><a href="#cb3-13"></a><span class="fu">ggplot</span>(<span class="at">data =</span> motorway_Delft) <span class="sc">+</span></span>
+<span id="cb3-14"><a href="#cb3-14"></a>  <span class="fu">geom_sf</span>(<span class="at">size =</span> <span class="fl">1.5</span>) <span class="sc">+</span></span>
+<span id="cb3-15"><a href="#cb3-15"></a>  <span class="fu">ggtitle</span>(<span class="st">"Mobility network of Delft"</span>, <span class="at">subtitle =</span> <span class="st">"Motorways"</span>) <span class="sc">+</span></span>
+<span id="cb3-16"><a href="#cb3-16"></a>  <span class="fu">coord_sf</span>()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section>
+<section id="challenge-4-3-mins" class="slide level2">
+<h2>Challenge 4: 🕚 <strong>3 mins</strong></h2>
+<p>In the previous example, we set the line widths to be 1, 0.75, 0.5, and 0.25. In our case line thicknesses are consistent with the hierarchy of the selected road types, but in some cases we might want to show a different hierarchy.</p>
+<p>Let’s create another plot where we show the different line types with the following thicknesses:</p>
+<ul>
+<li class="fragment">motorways size = 0.25</li>
+<li class="fragment">primary size = 0.75</li>
+<li class="fragment">secondary size = 0.5</li>
+<li class="fragment">cycleway size = 1</li>
+</ul>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_7339863b" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">03</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb4"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb4-1"><a href="#cb4-1"></a><span class="fu">levels</span>(<span class="fu">factor</span>(lines_Delft<span class="sc">$</span>highway))</span>
+<span id="cb4-2"><a href="#cb4-2"></a></span>
+<span id="cb4-3"><a href="#cb4-3"></a>line_widths <span class="ot">&lt;-</span> <span class="fu">c</span>(<span class="fl">0.25</span>, <span class="fl">0.75</span>, <span class="fl">0.5</span>, <span class="dv">1</span>)</span>
+<span id="cb4-4"><a href="#cb4-4"></a></span>
+<span id="cb4-5"><a href="#cb4-5"></a><span class="fu">ggplot</span>(<span class="at">data =</span> lines_Delft_selection) <span class="sc">+</span></span>
+<span id="cb4-6"><a href="#cb4-6"></a>  <span class="fu">geom_sf</span>(<span class="fu">aes</span>(<span class="at">size =</span> highway)) <span class="sc">+</span></span>
+<span id="cb4-7"><a href="#cb4-7"></a>  <span class="fu">scale_size_manual</span>(<span class="at">values =</span> line_widths) <span class="sc">+</span></span>
+<span id="cb4-8"><a href="#cb4-8"></a>  <span class="fu">labs</span>(<span class="at">size =</span> <span class="st">"Road Size"</span>) <span class="sc">+</span></span>
+<span id="cb4-9"><a href="#cb4-9"></a>  <span class="fu">ggtitle</span>(<span class="st">"Mobility network of Delft"</span>, <span class="at">subtitle =</span> <span class="st">"Roads &amp; Cycleways - Line width varies"</span>) <span class="sc">+</span></span>
+<span id="cb4-10"><a href="#cb4-10"></a>  <span class="fu">coord_sf</span>()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section>
+<section id="challenge-5-5-mins" class="slide level2">
+<h2>Challenge 5: 🕡 <strong>5 mins</strong></h2>
+<p>Create a plot that emphasizes only roads where bicycles are allowed, as follows:</p>
+<ul>
+<li class="fragment">Make the lines where bicycles are not allowed THINNER than the roads where bicycles are allowed.</li>
+<li class="fragment">Be sure to add a title and legend to your map.</li>
+<li class="fragment">You might consider a color palette that has all bike-friendly roads displayed in a bright color. All other lines can be black.</li>
+</ul>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_d7cb0eba" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb5"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb5-1"><a href="#cb5-1"></a><span class="fu">levels</span>(<span class="fu">factor</span>(lines_Delft_selection<span class="sc">$</span>highway))</span>
+<span id="cb5-2"><a href="#cb5-2"></a></span>
+<span id="cb5-3"><a href="#cb5-3"></a>lines_Delft_bicycle <span class="ot">&lt;-</span> lines_Delft <span class="sc">%&gt;%</span> </span>
+<span id="cb5-4"><a href="#cb5-4"></a>  <span class="fu">filter</span>(highway <span class="sc">==</span> <span class="st">"cycleway"</span>)</span>
+<span id="cb5-5"><a href="#cb5-5"></a></span>
+<span id="cb5-6"><a href="#cb5-6"></a><span class="fu">ggplot</span>() <span class="sc">+</span></span>
+<span id="cb5-7"><a href="#cb5-7"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> lines_Delft) <span class="sc">+</span></span>
+<span id="cb5-8"><a href="#cb5-8"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> lines_Delft_bicycle, <span class="at">color =</span> <span class="st">"magenta"</span>, <span class="at">size =</span> <span class="dv">2</span>) <span class="sc">+</span></span>
+<span id="cb5-9"><a href="#cb5-9"></a>  <span class="fu">ggtitle</span>(<span class="st">"Mobility network of Delft"</span>, <span class="at">subtitle =</span> <span class="st">"Roads dedicated to bikes"</span>) <span class="sc">+</span></span>
+<span id="cb5-10"><a href="#cb5-10"></a>  <span class="fu">coord_sf</span>()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section>
+<section id="challenge-6-3-mins" class="slide level2">
+<h2>Challenge 6: 🕜 <strong>3 mins</strong></h2>
+<p>Create a map of the municipal boundaries in the Netherlands, as follows:</p>
+<ul>
+<li class="fragment">Use the data located in your data folder: <code>nl-gemeenten.shp</code>.</li>
+<li class="fragment">Apply a line color to each state using its region value.</li>
+<li class="fragment">Add a legend.</li>
+</ul>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_f066ca9f" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">03</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb6"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb6-1"><a href="#cb6-1"></a>municipal_boundaries_NL <span class="ot">&lt;-</span> <span class="fu">st_read</span>(<span class="fu">here</span>(<span class="st">"episodes"</span>, <span class="st">"data"</span>, <span class="st">"nl-gemeenten.shp"</span>))</span>
+<span id="cb6-2"><a href="#cb6-2"></a><span class="fu">str</span>(municipal_boundaries_NL)</span>
+<span id="cb6-3"><a href="#cb6-3"></a><span class="fu">levels</span>(<span class="fu">factor</span>(municipal_boundaries_NL<span class="sc">$</span>ligtInPr_1))</span>
+<span id="cb6-4"><a href="#cb6-4"></a></span>
+<span id="cb6-5"><a href="#cb6-5"></a><span class="fu">ggplot</span>(<span class="at">data =</span> municipal_boundaries_NL) <span class="sc">+</span></span>
+<span id="cb6-6"><a href="#cb6-6"></a>  <span class="fu">geom_sf</span>(<span class="fu">aes</span>(<span class="at">color =</span> ligtInPr_1), <span class="at">size =</span> <span class="dv">1</span>) <span class="sc">+</span></span>
+<span id="cb6-7"><a href="#cb6-7"></a>  <span class="fu">ggtitle</span>(<span class="st">"Contiguous NL Municipal Boundaries"</span>) <span class="sc">+</span></span>
+<span id="cb6-8"><a href="#cb6-8"></a>  <span class="fu">coord_sf</span>()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section></section>
+<section>
+<section id="plot-multiple-shapefiles" class="title-slide slide level1 center">
+<h1>Plot multiple shapefiles</h1>
+
+</section>
+<section id="challenge-7-5-mins" class="slide level2">
+<h2>Challenge 7: 🕘 <strong>5 mins</strong></h2>
+<p>Create a map of leisure locations only including <code>playground</code> and <code>picnic_table</code>:</p>
+<ul>
+<li class="fragment"><p>Color each point by the leisure type.</p></li>
+<li class="fragment"><p>Overlay this layer on top of the <code>lines_Delft</code> layer (the streets).</p></li>
+<li class="fragment"><p>Create a custom legend that applies line symbols to lines and point symbols to the points.</p></li>
+<li class="fragment"><p>Extra: Modify the previous plot. Tell R to plot each point, using a different symbol of shape value.</p></li>
+</ul>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_eec5b114" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb7"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb7-1"><a href="#cb7-1"></a>leisure_locations_selection <span class="ot">&lt;-</span> <span class="fu">st_read</span>(<span class="fu">here</span>(<span class="st">"episodes"</span>, <span class="st">"data"</span>, <span class="st">"delft-leisure.shp"</span>)) <span class="sc">%&gt;%</span> </span>
+<span id="cb7-2"><a href="#cb7-2"></a>  <span class="fu">filter</span>(leisure <span class="sc">%in%</span> <span class="fu">c</span>(<span class="st">"playground"</span>, <span class="st">"picnic_table"</span>))</span>
+<span id="cb7-3"><a href="#cb7-3"></a></span>
+<span id="cb7-4"><a href="#cb7-4"></a>blue_orange <span class="ot">&lt;-</span> <span class="fu">c</span>(<span class="st">"cornflowerblue"</span>, <span class="st">"darkorange"</span>)</span>
+<span id="cb7-5"><a href="#cb7-5"></a></span>
+<span id="cb7-6"><a href="#cb7-6"></a>p <span class="ot">&lt;-</span> <span class="fu">ggplot</span>() <span class="sc">+</span> </span>
+<span id="cb7-7"><a href="#cb7-7"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> lines_Delft_selection, <span class="fu">aes</span>(<span class="at">color =</span> highway)) <span class="sc">+</span> </span>
+<span id="cb7-8"><a href="#cb7-8"></a>  <span class="fu">scale_color_manual</span>(<span class="at">name =</span> <span class="st">"Line Type"</span>, <span class="at">values =</span> road_colors) <span class="sc">+</span></span>
+<span id="cb7-9"><a href="#cb7-9"></a>  <span class="fu">ggtitle</span>(<span class="st">"Road network and leisure"</span>)</span>
+<span id="cb7-10"><a href="#cb7-10"></a></span>
+<span id="cb7-11"><a href="#cb7-11"></a>p <span class="sc">+</span></span>
+<span id="cb7-12"><a href="#cb7-12"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> leisure_locations_selection, <span class="fu">aes</span>(<span class="at">fill =</span> leisure), <span class="at">shape =</span> <span class="dv">21</span>) <span class="sc">+</span></span>
+<span id="cb7-13"><a href="#cb7-13"></a>  <span class="fu">scale_fill_manual</span>(<span class="at">name =</span> <span class="st">"Leisure Type"</span>, <span class="at">values =</span> blue_orange)</span>
+<span id="cb7-14"><a href="#cb7-14"></a></span>
+<span id="cb7-15"><a href="#cb7-15"></a>p <span class="sc">+</span> </span>
+<span id="cb7-16"><a href="#cb7-16"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> leisure_locations_selection, <span class="fu">aes</span>(<span class="at">fill =</span> leisure, <span class="at">shape =</span> leisure), <span class="at">size =</span> <span class="dv">3</span>) <span class="sc">+</span></span>
+<span id="cb7-17"><a href="#cb7-17"></a>  <span class="fu">scale_fill_manual</span>(<span class="at">name =</span> <span class="st">"Leisure Type"</span>, <span class="at">values =</span> blue_orange) <span class="sc">+</span></span>
+<span id="cb7-18"><a href="#cb7-18"></a>  <span class="fu">scale_shape_manual</span>(<span class="at">name =</span> <span class="st">"Leisure Type"</span>, <span class="at">values =</span> <span class="fu">c</span>(<span class="dv">21</span>, <span class="dv">22</span>))</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+</div>
+</section></section>
+<section>
+<section id="handling-spatial-projections" class="title-slide slide level1 center">
+<h1>Handling spatial projections</h1>
+
+</section>
+<section id="challenge-8-3-mins" class="slide level2">
+<h2>Challenge 8: 🕰 <strong>3 mins</strong></h2>
+<p>Create a map of the South Holland, as follows:</p>
+<ol type="1">
+<li class="fragment">Import <code>nl-gemeenten.shp</code> and filter only the municipalities in South Holland.</li>
+<li class="fragment">Plot it and adjust line width as necessary.</li>
+<li class="fragment">Layer the boundary of Delft onto the plot.</li>
+<li class="fragment">Add a title.</li>
+<li class="fragment">Add a legend that shows both the province boundaries (as a line) and the boundary of Delft (as a filled polygon).</li>
+</ol>
+<div class="cell">
+<div class="cell-output-display">
+<div class="countdown" id="timer_96de5618" data-update-every="1" tabindex="0" style="right:0;bottom:0;">
+<div class="countdown-controls"><button class="countdown-bump-down">−</button><button class="countdown-bump-up">+</button></div>
+<code class="countdown-time"><span class="countdown-digits minutes">03</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
+</div>
+</div>
+</div>
+<div class="fragment">
+<div class="cell">
+<div class="sourceCode cell-code" id="cb8"><pre class="sourceCode numberSource r number-lines code-with-copy"><code class="sourceCode r"><span id="cb8-1"><a href="#cb8-1"></a>boundary_ZH <span class="ot">&lt;-</span> municipal_boundary_NL <span class="sc">%&gt;%</span> </span>
+<span id="cb8-2"><a href="#cb8-2"></a>  <span class="fu">filter</span>(ligtInPr_1 <span class="sc">==</span> <span class="st">"Zuid-Holland"</span>)</span>
+<span id="cb8-3"><a href="#cb8-3"></a></span>
+<span id="cb8-4"><a href="#cb8-4"></a><span class="fu">ggplot</span>() <span class="sc">+</span></span>
+<span id="cb8-5"><a href="#cb8-5"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> boundary_ZH, <span class="fu">aes</span>(<span class="at">color =</span><span class="st">"color"</span>), <span class="at">show.legend =</span> <span class="st">"line"</span>) <span class="sc">+</span></span>
+<span id="cb8-6"><a href="#cb8-6"></a>  <span class="fu">scale_color_manual</span>(<span class="at">name =</span> <span class="st">""</span>, <span class="at">labels =</span> <span class="st">"Municipal Boundaries"</span>, <span class="at">values =</span> <span class="fu">c</span>(<span class="st">"color"</span> <span class="ot">=</span> <span class="st">"gray18"</span>)) <span class="sc">+</span></span>
+<span id="cb8-7"><a href="#cb8-7"></a>  <span class="fu">geom_sf</span>(<span class="at">data =</span> boundary_Delft, <span class="fu">aes</span>(<span class="at">shape =</span> <span class="st">"shape"</span>), <span class="at">color =</span> <span class="st">"purple"</span>, <span class="at">fill =</span> <span class="st">"purple"</span>) <span class="sc">+</span></span>
+<span id="cb8-8"><a href="#cb8-8"></a>  <span class="fu">scale_shape_manual</span>(<span class="at">name =</span> <span class="st">""</span>, <span class="at">labels =</span> <span class="st">"Municipality of Delft"</span>, <span class="at">values =</span> <span class="fu">c</span>(<span class="st">"shape"</span> <span class="ot">=</span> <span class="dv">19</span>)) <span class="sc">+</span></span>
+<span id="cb8-9"><a href="#cb8-9"></a>  <span class="fu">ggtitle</span>(<span class="st">"Delft location in South Holland"</span>) <span class="sc">+</span></span>
+<span id="cb8-10"><a href="#cb8-10"></a>  <span class="fu">theme</span>(<span class="at">legend.background =</span> <span class="fu">element_rect</span>(<span class="at">color =</span> <span class="cn">NA</span>)) <span class="sc">+</span></span>
+<span id="cb8-11"><a href="#cb8-11"></a>  <span class="fu">coord_sf</span>()</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
+</div>
+<div class="footer footer-default">
+<p>Geospatial Data Carpentry for Urbanism</p>
+</div>
+</div>
+</section></section>
+    </div>
+  </div>
+
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+        // flash "checked"
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+</body></html>
\ No newline at end of file
diff --git a/aio.html b/aio.html
index 95e1c089..b7dd38f6 100644
--- a/aio.html
+++ b/aio.html
@@ -2216,9 +2216,9 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
-<li>Know the difference between point, line, and polygon vector
-data.</li>
+<li>Differentiate between point, line, and polygon vector data.</li>
 <li>Load vector data into R.</li>
 <li>Access the attributes of a vector object in R.</li>
 </ul>
@@ -2235,25 +2235,23 @@ <h3 class="card-title">Objectives</h3>
 <h3 class="callout-title">Prerequisite<a class="anchor" aria-label="anchor" href="#prereq1"></a>
 </h3>
 <div class="callout-content">
-<p>If you have not installed the <code>sf</code> package yet, run
-<code>install.packages("sf")</code> first. Note that the <code>sf</code>
-package has some external dependencies, namely GEOS, PROJ.4, GDAL and
-UDUNITS, which need to be installed beforehand. Follow the workshop <a href="">setup instructions</a> for the installation of <code>sf</code>
-and its dependencies.</p>
+<p>In this lesson you will work with the <code>sf</code> package. Note
+that the <code>sf</code> package has some external dependencies, namely
+GEOS, PROJ.4, GDAL and UDUNITS, which need to be installed beforehand.
+Before starting the lesson, follow the workshop <a href="index.html#setup">setup instructions</a> for the installation of
+<code>sf</code> and its dependencies.</p>
 </div>
 </div>
 </div>
 <p>First we need to load the packages we will use in this lesson. We
-will use the packages <code>tidyverse</code> and <code>here</code> with
-which you are already familiar from the previous lesson. In addition, we
-need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
+will use the <code>tidyverse</code> package with which you are already
+familiar from the previous lesson. In addition, we need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
 working with spatial vector data.</p>
 <div class="codewrapper sourceCode" id="cb1">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># tools for wrangling, reshaping and visualizing data</span></span>
-<span><span class="kw">library</span><span class="op">(</span><span class="va">here</span><span class="op">)</span>       <span class="co"># managing paths</span></span>
+<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># wrangle, reshape and visualize data</span></span>
 <span><span class="kw">library</span><span class="op">(</span><span class="va">sf</span><span class="op">)</span>         <span class="co"># work with spatial vector data</span></span></code></pre>
 </div>
 <div id="the-sf-package" class="callout callout">
@@ -2266,24 +2264,26 @@ <h3 class="callout-title">The<code>sf</code>package<a class="anchor" aria-label=
 <div class="callout-content">
 <p><code>sf</code> stands for Simple Features which is a standard
 defined by the Open Geospatial Consortium for storing and accessing
-geospatial vector data. PostGIS uses the same standard; so those of you
-who used PostGIS, might find some resemblances with the functions used
-by the <code>sf</code> package.</p>
+geospatial vector data. PostGIS, for instance, uses the same standard,
+so PostGIS users might recognise the functions used by the
+<code>sf</code> package.</p>
 </div>
 </div>
 </div>
 <section id="import-shapefiles"><h2 class="section-heading">Import shapefiles<a class="anchor" aria-label="anchor" href="#import-shapefiles"></a>
 </h2>
 <hr class="half-width">
-<p>Let’s start by opening a shapefile. Shapefiles a common file format
-to store spatial vector data used in GIS software. We will read a
-shapefile with the administrative boundary of Delft with the function
+<p>Let’s start by opening a shapefile. Shapefiles are a common file
+format to store spatial vector data used in GIS software. Note that a
+shapefile consists of multiple files and it is important to keep them
+all together in the same location. We will read a shapefile with the
+administrative boundary of Delft with the function
 <code>st_read()</code> from the <code>sf</code> package.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span>, quiet <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="all-sf-functions-start-with-st_" class="callout callout">
 <div class="callout-square">
@@ -2295,22 +2295,27 @@ <h3 class="callout-title">All<code>sf</code>functions start with<code>st_</code>
 <div class="callout-content">
 <p>Note that all functions from the <code>sf</code> package start with
 the standard prefix <code>st_</code> which stands for Spatial Type. This
-is helpful in at least two ways: (1) it makes the interaction with or
-translation to/from software using the simple features standard like
-PostGIS easy, and (2) it allows for easy autocompletion of function
-names in RStudio.</p>
+is helpful in at least two ways:</p>
+<ol style="list-style-type: decimal">
+<li>it allows for easy autocompletion of function names in RStudio,
+and</li>
+<li>it makes the interaction with or translation to/from software using
+the simple features standard like PostGIS easy.</li>
+</ol>
 </div>
 </div>
 </div>
 </section><section id="spatial-metadata"><h2 class="section-heading">Spatial Metadata<a class="anchor" aria-label="anchor" href="#spatial-metadata"></a>
 </h2>
 <hr class="half-width">
-<p>The <code>st_read()</code> function gave us a message with a summary
-of metadata about the file that was read in. To examine the metadata in
+<p>By default (with <code>quiet = FALSE</code>), the
+<code>st_read()</code> function provides a message with a summary of
+metadata about the file that was read in. To examine the metadata in
 more detail, we can use other, more specialised, functions from the
-<code>sf</code> package. The <code>st_geometry_type()</code> function,
-for instance, gives us information about the geometry type, which in
-this case is <code>POLYGON</code>.</p>
+<code>sf</code> package.</p>
+<p>The <code>st_geometry_type()</code> function, for instance, gives us
+information about the geometry type, which in this case is
+<code>POLYGON</code>.</p>
 <div class="codewrapper sourceCode" id="cb3">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -2325,7 +2330,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </div>
 <p>The <code>st_crs()</code> function returns the coordinate reference
 system (CRS) used by the shapefile, which in this case is
-<code>WGS84</code> and has the unique reference code
+<code>WGS 84</code> and has the unique reference code
 <code>EPSG: 4326</code>.</p>
 <div class="codewrapper sourceCode" id="cb5">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2369,7 +2374,7 @@ <h3 class="callout-title">Examining the output of<code>st_crs()</code><a class="
 </div>
 </div>
 <p>The <code>st_bbox()</code> function shows the extent of the layer. As
-<code>WGS84</code> is a <strong>geographic CRS</strong>, the extent of
+<code>WGS 84</code> is a <strong>geographic CRS</strong>, the extent of
 the shapefile is displayed in degrees.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2388,62 +2393,34 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 our shapefile, we will use the <code>st_transform()</code> function. For
 the <code>crs</code> argument we can use the EPSG code of the CRS we
 want to use, which is <code>28992</code> for the
-<code>Amersfort / RD New</code> projection.</p>
+<code>Amersfort / RD New</code> projection. To check the EPSG code of
+any CRS, we can check this website: <a href="https://epsg.io/" class="external-link uri">https://epsg.io/</a></p>
 <div class="codewrapper sourceCode" id="cb9">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_transform</span><span class="op">(</span><span class="va">boundary_Delft</span>, <span class="fl">28992</span><span class="op">)</span></span>
-<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span></span></code></pre>
+<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">Name</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>Coordinate Reference System:
-  User input: EPSG:28992 
-  wkt:
-PROJCRS["Amersfoort / RD New",
-    BASEGEOGCRS["Amersfoort",
-        DATUM["Amersfoort",
-            ELLIPSOID["Bessel 1841",6377397.155,299.1528128,
-                LENGTHUNIT["metre",1]]],
-        PRIMEM["Greenwich",0,
-            ANGLEUNIT["degree",0.0174532925199433]],
-        ID["EPSG",4289]],
-    CONVERSION["RD New",
-        METHOD["Oblique Stereographic",
-            ID["EPSG",9809]],
-        PARAMETER["Latitude of natural origin",52.1561605555556,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8801]],
-        PARAMETER["Longitude of natural origin",5.38763888888889,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8802]],
-        PARAMETER["Scale factor at natural origin",0.9999079,
-            SCALEUNIT["unity",1],
-            ID["EPSG",8805]],
-        PARAMETER["False easting",155000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8806]],
-        PARAMETER["False northing",463000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8807]]],
-    CS[Cartesian,2],
-        AXIS["easting (X)",east,
-            ORDER[1],
-            LENGTHUNIT["metre",1]],
-        AXIS["northing (Y)",north,
-            ORDER[2],
-            LENGTHUNIT["metre",1]],
-    USAGE[
-        SCOPE["Engineering survey, topographic mapping."],
-        AREA["Netherlands - onshore, including Waddenzee, Dutch Wadden Islands and 12-mile offshore coastal zone."],
-        BBOX[50.75,3.2,53.7,7.22]],
-    ID["EPSG",28992]]</code></pre>
+<pre class="output" tabindex="0"><code>[1] "Amersfoort / RD New"</code></pre>
+</div>
+<div class="codewrapper sourceCode" id="cb11">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
 <p>Notice that the bounding box is measured in meters after the
 transformation.</p>
-<div class="codewrapper sourceCode" id="cb11">
+<div class="codewrapper sourceCode" id="cb13">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2455,9 +2432,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81743.00 442446.21  87703.78 449847.95 </code></pre>
 </div>
+<div class="codewrapper sourceCode" id="cb15">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">units_gdal</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] "metre"</code></pre>
+</div>
 <p>We confirm the transformation by examining the reprojected
 shapefile.</p>
-<div class="codewrapper sourceCode" id="cb13">
+<div class="codewrapper sourceCode" id="cb17">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2482,8 +2470,9 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#callout4"></a>
 </h3>
 <div class="callout-content">
-<p>More about CRS in <a href="">Handling Spatial Projection &amp;
-CRS</a>.</p>
+<p>Read more about Coordinate Reference Systems <a href="https://datacarpentry.org/organization-geospatial/03-crs.html" class="external-link">here</a>.
+We will also practice transformation between CRS in <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial
+Projection &amp; CRS</a>.</p>
 </div>
 </div>
 </div>
@@ -2491,11 +2480,11 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </h2>
 <hr class="half-width">
 <p>Now, let’s plot this shapefile. You are already familiar with the
-<code>ggplot2</code> package from <a href="">Introduction to
-Visualisation</a>. <code>ggplot2</code> has special <code>geom_</code>
-functions for spatial data. We will use the <code>geom_sf()</code>
-function for <code>sf</code> data.</p>
-<div class="codewrapper sourceCode" id="cb15">
+<code>ggplot2</code> package from <a href="04-intro-to-visualisation.html">Introduction to Visualisation</a>.
+<code>ggplot2</code> has special <code>geom_</code> functions for
+spatial data. We will use the <code>geom_sf()</code> function for
+<code>sf</code> data.</p>
+<div class="codewrapper sourceCode" id="cb19">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2504,18 +2493,18 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Delft Administrative Boundary"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span>  <span class="co"># this is needed to display the axes in meters</span></span></code></pre>
 </div>
-<figure><img src="fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-1-import-line-and-point-vector-layers" class="callout challenge">
+<figure><img src="fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-import-line-and-point-vector-layers" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="challenge-1-import-line-and-point-vector-layers" class="callout-inner">
-<h3 class="callout-title">Challenge 1: Import line and point vector
-layers<a class="anchor" aria-label="anchor" href="#challenge-1-import-line-and-point-vector-layers"></a>
+<div id="challenge-import-line-and-point-vector-layers" class="callout-inner">
+<h3 class="callout-title">Challenge: Import line and point vector
+layers<a class="anchor" aria-label="anchor" href="#challenge-import-line-and-point-vector-layers"></a>
 </h3>
 <div class="callout-content">
 <p>Read in <code>delft-streets.shp</code> and
 <code>delft-leisure.shp</code> and assign them to
-<code>lines_Delft</code> and <code>point_Delft</code> respectively.
+<code>lines_Delft</code> and <code>points_Delft</code> respectively.
 Answer the following questions:</p>
 <ol style="list-style-type: decimal">
 <li>What type of R spatial object is created when you import each
@@ -2532,44 +2521,47 @@ <h3 class="callout-title">Challenge 1: Import line and point vector
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
-<div class="codewrapper sourceCode" id="cb16">
+<div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">lines_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-streets.shp"</span><span class="op">)</span></span>
-<span><span class="va">point_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
+<span><span class="va">points_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
 </div>
-<p>We can check the type of data with the <code>class()</code> function
-from base R. Both <code>lines_Delft</code> and <code>point_Delft</code>
-are objects of class <code>"sf"</code>, which extends the
-<code>"data.frame"</code> class.</p>
-<div class="codewrapper sourceCode" id="cb17">
+<p>We can check the type of type of geometry with the
+<code>st_geometry_type()</code> function. <code>lines_Delft</code>
+contains <code>"LINESTRING"</code> geometry and
+<code>points_Delft</code> is made of <code>"POINT"</code>
+geometries.</p>
+<div class="codewrapper sourceCode" id="cb21">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">1</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] LINESTRING
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb19">
+<div class="codewrapper sourceCode" id="cb23">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">2</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] POINT
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<p><code>lines_Delft</code> and <code>point_Delft</code> are in the
+<p><code>lines_Delft</code> and <code>points_Delft</code> are in the
 correct CRS.</p>
-<div class="codewrapper sourceCode" id="cb21">
+<div class="codewrapper sourceCode" id="cb25">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2580,11 +2572,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb23">
+<div class="codewrapper sourceCode" id="cb27">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2594,8 +2586,8 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <p>When looking at the bounding boxes with the <code>st_bbox()</code>
 function, we see the spatial extent of the two objects in a projected
 CRS using meters as units. <code>lines_Delft()</code> and
-<code>point_Delft</code> have similar extents.</p>
-<div class="codewrapper sourceCode" id="cb25">
+<code>points_Delft</code> have similar extents.</p>
+<div class="codewrapper sourceCode" id="cb29">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2607,11 +2599,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81759.58 441223.13  89081.41 449845.81 </code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb27">
+<div class="codewrapper sourceCode" id="cb31">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2636,7 +2628,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul>
@@ -2672,6 +2664,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li><p>Query attributes of a vector object.</p></li>
 <li><p>Subset vector objects using specific attribute values.</p></li>
@@ -2762,13 +2755,13 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </div>
 </div>
 <p>We can also preview the content of the object by looking at the first
-6 rows with the <code>head()</code> function, which is in the case of an
-<code>sf</code> object the same as examining the object directly.</p>
+6 rows with the <code>head()</code> function, which in the case of an
+<code>sf</code> object is similar to examining the object directly.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span> <span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2855,6 +2848,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 [21] "tertiary"       "tertiary_link"  "track"          "trunk"         
 [25] "trunk_link"     "unclassified"  </code></pre>
 </div>
+<p>Note that this way the values are shown by default in alphabetical
+order and <code>NA</code>s are not displayed, whereas using
+<code>unique()</code> returns unique values in the order of their
+occurrence in the data frame and it also shows <code>NA</code>
+values.</p>
 </div>
 </div>
 </div>
@@ -2969,7 +2967,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="co"># point_Delft</span></span></code></pre>
 </div>
-<p>However, this is not a good approach as the first rows might still
+<p>We have our answer (<code>sports_centre</code> is the third value),
+but in general this is not a good approach as the first rows might still
 have many <code>NA</code>s and three distinct values might still not be
 present in the first <code>n</code> rows of the data frame. To remove
 <code>NA</code>s, we can use the function <code>na.omit()</code> on the
@@ -2988,19 +2987,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] "picnic_table"  "marina"        "marina"        "sports_centre"
 [5] "sports_centre" "playground"   </code></pre>
 </div>
-<p>To show only unique values, we can use the <code>unique()</code>
-function to only see the first occurrence of each distinct value (note
-that <code>NA</code> will still be included once).</p>
+<p>To show only unique values, we can use the <code>levels()</code>
+function on a factor to only see the first occurrence of each distinct
+value. Note <code>NA</code>s are dropped in this case and that we get
+the first three of the unique alphabetically ordered values.</p>
 <div class="codewrapper sourceCode" id="cb24">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">unique</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">levels</span><span class="op">(</span><span class="fu">factor</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "picnic_table" "marina"       NA            </code></pre>
+<pre class="output" tabindex="0"><code>[1] "dance"       "dog_park"    "escape_game"</code></pre>
 </div>
 <ol start="3" style="list-style-type: decimal">
 <li>To see a list of all attribute names, we can use the
@@ -3103,6 +3103,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 </h3>
 <div class="callout-content">
 <!-- 7 minutes -->
+<p>Challenge: Now with motorways (and pedestrian streets)</p>
 <ol style="list-style-type: decimal">
 <li>Create a new object that only contains the motorways in Delft.</li>
 <li>How many features does the new object have?</li>
@@ -3201,7 +3202,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] 48</code></pre>
 </div>
 <ol start="4" style="list-style-type: decimal">
-<li>Plot the motorways</li>
+<li>Plot the motorways.</li>
 </ol>
 <div class="codewrapper sourceCode" id="cb43">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3213,7 +3214,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal">
-<li>Same steps with pedestrian streets</li>
+<li>Follow the same steps with pedestrian streets.</li>
 </ol>
 <div class="codewrapper sourceCode" id="cb44">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3292,8 +3293,10 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 expression in which we only filter the rows of our data frame that have
 one of the four given values <code>"motorway"</code>,
 <code>"primary"</code>, <code>"secondary"</code>, and
-<code>"cycleway"</code>. We also make sure that the highway column is a
-factor column.</p>
+<code>"cycleway"</code>. Note that we do this with the <code>%in</code>
+operator which is a more compact equivalent of a series of conditions
+joined by the <code>|</code> (or) operator. We also make sure that the
+highway column is a factor column.</p>
 <div class="codewrapper sourceCode" id="cb51">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3307,7 +3310,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <p>Next we define the four colors we want to use, one for each type of
 road in our vector object. Note that in R you can use named colors like
 <code>"blue"</code>, <code>"green"</code>, <code>"navy"</code>, and
-<code>"purple"</code>. A full list of named colors can be listed with
+<code>"purple"</code>. If you are using RStudio, you will see the named
+colors previewed in line. A full list of named colors can be listed with
 the <code>colors()</code> function.</p>
 <div class="codewrapper sourceCode" id="cb52">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3359,12 +3363,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">scale_linewidth_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">line_widths</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-line-width-by-attribute" class="callout challenge">
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-line-width-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-line-width-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot line width by attribute<a class="anchor" aria-label="anchor" href="#plot-line-width-by-attribute"></a>
+<div id="challenge-plot-line-width-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot line width by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-line-width-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <p>In the example above, we set the line widths to be 1, 0.75, 0.5, and
@@ -3434,13 +3438,14 @@ <h2 id="add-plot-legend">Add plot legend<a class="anchor" aria-label="anchor" hr
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
+<code class="sourceCode R"><span><span class="va">p1</span> <span class="op">&lt;-</span> <span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
 <span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Default Legend"</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span>
+<span><span class="va">p1</span></span></code></pre>
 </div>
 <figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-34-1.png" alt="Mobility network in Delft using thicker lines than the previous example." class="figure mx-auto d-block"><figcaption>
 Mobility network in Delft using thicker lines than the previous example.
@@ -3448,15 +3453,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
+<code class="sourceCode R"><span><span class="va">p2</span> <span class="op">&lt;-</span> <span class="va">p1</span> <span class="op">+</span></span>
 <span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3467,33 +3466,21 @@ <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left">
 Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
 generated.</code></pre>
 </div>
-<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft with large-font and border around
-the legend.
-</figcaption></figure><div class="codewrapper sourceCode" id="cb63">
+<div class="codewrapper sourceCode" id="cb63">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">new_colors</span> <span class="op">&lt;-</span> <span class="fu">c</span><span class="op">(</span><span class="st">"springgreen"</span>, <span class="st">"blue"</span>, <span class="st">"magenta"</span>, <span class="st">"orange"</span><span class="op">)</span></span>
-<span></span>
-<span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">new_colors</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">p2</span></span></code></pre>
 </div>
-<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><div id="plot-lines-by-attributes" class="callout challenge">
+<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
+Map of the mobility network in Delft with large-font and border around
+the legend.
+</figcaption></figure><div id="challenge-plot-lines-by-attributes" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-lines-by-attributes" class="callout-inner">
-<h3 class="callout-title">Plot lines by attributes<a class="anchor" aria-label="anchor" href="#plot-lines-by-attributes"></a>
+<div id="challenge-plot-lines-by-attributes" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot lines by attributes<a class="anchor" aria-label="anchor" href="#challenge-plot-lines-by-attributes"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -3557,17 +3544,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network in Delft"</span>, subtitle <span class="op">=</span> <span class="st">"Roads dedicated to Bikes"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
 </div>
 </div>
 </div>
 </div>
-<div id="plot-polygon-by-attribute" class="callout challenge">
+<div id="challenge-plot-polygon-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-polygon-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#plot-polygon-by-attribute"></a>
+<div id="challenge-plot-polygon-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-polygon-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -3588,7 +3575,7 @@ <h4 class="accordion-header" id="headingSolution5">Show me the solution</h4>
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="fu">here</span><span class="op">(</span><span class="st">"data"</span>, <span class="st">"nl-gemeenten.shp"</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/nl-gemeenten.shp"</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3648,7 +3635,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
 </div>
 </div>
 </div>
@@ -3701,6 +3688,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li>Plot multiple vector layers in the same plot.</li>
 <li>Apply custom symbols to spatial objects in a plot.</li>
@@ -3710,18 +3698,17 @@ <h3 class="card-title">Objectives</h3>
 </div>
 </div>
 </div>
-<p>This episode builds upon the <a href="">previous episode</a> to work
-with vector layers in R and explore how to plot multiple vector
-layers.</p>
+<p>This episode builds upon the <a href="10-explore-and-plot-by-vector-layer-attributes.html">previous
+episode</a> to work with vector layers in R and explore how to plot
+multiple vector layers.</p>
 <section id="load-the-data"><h2 class="section-heading">Load the data<a class="anchor" aria-label="anchor" href="#load-the-data"></a>
 </h2>
 <hr class="half-width">
-<p>To work with vector data in R, we can use the <code>sf</code>
-library. The <code>terra</code> package also allows us to explore
-metadata using similar commands for both raster and vector files. Make
-sure that you have these packages loaded.</p>
+<p>To work with vector data in R, we use the <code>sf</code> library.
+Make sure that it is loaded.</p>
 <p>We will continue to work with the three ESRI shapefiles that we
-loaded in the <a href="">Open and Plot Vector Layers</a> episode.</p>
+loaded in the <a href="09-open-and-plot-vector-layers.html">Open and
+Plot Vector Layers</a> episode.</p>
 </section><section id="plotting-multiple-vector-layers"><h2 class="section-heading">Plotting Multiple Vector Layers<a class="anchor" aria-label="anchor" href="#plotting-multiple-vector-layers"></a>
 </h2>
 <hr class="half-width">
@@ -3747,14 +3734,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the symbology (the colors and
-symbols) that we used to create the plot above. For example, it might be
-good if the lines were symbolized as lines. In the previous episode, you
-may have noticed that the default legend behavior for
-<code>geom_sf</code> is to draw a ‘patch’ for each legend entry. If you
-want the legend to draw lines or points, you need to add an instruction
-to the <code>geom_sf</code> call - in this case,
-<code>show.legend = 'line'</code>.</p>
+<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the functions
+<code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code>.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3786,9 +3768,15 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-3-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>We notice that there are quite some playgrounds in the residential
 parts of Delft, whereas on campus there is a concentration of picnic
 tables. So that is what our next challenge is about.</p>
-<div class="section level3">
-<h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-label="anchor" href="#challenge-7-5-minutes"></a>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout challenge">
+<div class="callout-square">
+<i class="callout-icon" data-feather="zap"></i>
+</div>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout-inner">
+<h3 class="callout-title">Challenge: Visualising multiple layers with a
+custom legend<a class="anchor" aria-label="anchor" href="#challenge-visualising-multiple-layers-with-a-custom-legend"></a>
 </h3>
+<div class="callout-content">
 <p>Create a map of leisure locations only including
 <code>playground</code> and <code>picnic_table</code>, with each point
 colored by the leisure type. Overlay this layer on top of the
@@ -3796,6 +3784,16 @@ <h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-lab
 that applies line symbols to lines and point symbols to the points.</p>
 <p>Modify the plot above. Tell R to plot each point, using a different
 symbol of shape value.</p>
+</div>
+</div>
+</div>
+<div id="accordionSolution1" class="accordion challenge-accordion accordion-flush">
+<div class="accordion-item">
+<button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
+  <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
+</button>
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb4">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3839,7 +3837,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span>, <span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">leisure_locations_selection</span>, <span class="fu">aes</span><span class="op">(</span>fill <span class="op">=</span> <span class="va">leisure</span><span class="op">)</span>, </span>
-<span>          shape <span class="op">=</span> <span class="fl">21</span>, show.legend <span class="op">=</span> <span class="st">'point'</span><span class="op">)</span> <span class="op">+</span> </span>
+<span>          shape <span class="op">=</span> <span class="fl">21</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Line Type"</span>, values <span class="op">=</span> <span class="va">road_colors</span>,</span>
 <span>     guide <span class="op">=</span> <span class="fu">guide_legend</span><span class="op">(</span>override.aes <span class="op">=</span> <span class="fu">list</span><span class="op">(</span>linetype <span class="op">=</span> <span class="st">"solid"</span>, shape <span class="op">=</span> <span class="cn">NA</span><span class="op">)</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_fill_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Soil Type"</span>, values <span class="op">=</span> <span class="va">blue_orange</span>,</span>
@@ -3862,7 +3860,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Road network and leisure"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><!-- End of challenge --><div id="keypoints1" class="callout keypoints">
+<figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+</div>
+</div>
+</div>
+</div>
+<div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
 <i class="callout-icon" data-feather="key"></i>
 </div>
@@ -3874,10 +3877,8 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul>
 </div>
 </div>
@@ -3886,7 +3887,6 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 Place links that you need to refer to multiple times across pages here. Delete
 any links that you are not going to use. 
  -->
-</div>
 </section></section><section id="aio-12-handling-spatial-projection-and-crs"><p>Content from <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial Projections &amp; CRS</a></p>
 <hr>
 <p>Last updated on 2024-01-29 |
@@ -3912,6 +3912,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li>Plot vector objects with different CRSs in the same plot.</li>
 </ul>
@@ -4055,19 +4056,21 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Map of Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-multiple-layers-of-spatial-data" class="callout challenge">
+<figure><img src="fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-multiple-layers-of-spatial-data" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-multiple-layers-of-spatial-data" class="callout-inner">
-<h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor" aria-label="anchor" href="#plot-multiple-layers-of-spatial-data"></a>
+<div id="challenge-plot-multiple-layers-of-spatial-data" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot multiple layers of spatial
+data<a class="anchor" aria-label="anchor" href="#challenge-plot-multiple-layers-of-spatial-data"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
 <p>Create a map of South Holland as follows:</p>
 <ol style="list-style-type: decimal">
-<li>Import and plot <code>nl-gemeenten.shp</code>. Adjust line width as
-necessary.</li>
+<li>Import <code>nl-gemeenten.shp</code> and filter only the
+municipalities in South Holland.</li>
+<li>Plot it and adjust line width as necessary.</li>
 <li>Layer the boundary of Delft onto the plot.</li>
 <li>Add a title.</li>
 <li>Add a legend that shows both the province boundaries (as a line) and
@@ -4081,7 +4084,7 @@ <h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb18">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -4112,12 +4115,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 </h2>
 <hr class="half-width">
 <p>To save a file, use the <code>st_write()</code> function from the
-<code>sf</code> package.</p>
+<code>sf</code> package. Although <code>sf</code> guesses the driver
+needed for a specified output file name from its extension, this can be
+made explicitly via the <code>driver</code> argument. In our case
+<code>driver = "ESRI Shapefile"</code> ensures that the output is
+correctly saved as a <code>.shp</code> file.</p>
 <div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="sourceCode r" tabindex="0"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true" tabindex="-1"></a><span class="fu">st_write</span>(leisure_locations_selection,</span>
-<span id="cb20-2"><a href="#cb20-2" aria-hidden="true" tabindex="-1"></a>         <span class="st">"data/leisure_locations_selection.shp"</span>), driver <span class="ot">=</span> <span class="st">"ESRI Shapefile"</span><span class="er">)</span></span></code></pre>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_write</span><span class="op">(</span><span class="va">leisure_locations_selection</span>,</span>
+<span>         <span class="st">"data/leisure_locations_selection.shp"</span>, driver <span class="op">=</span> <span class="st">"ESRI Shapefile"</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
@@ -4522,7 +4530,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <p><code>+units=m</code> in the output of the code above tells us that
 our data is in meters (m).</p>
@@ -4710,7 +4718,7 @@ <h3 class="callout-title">Challenge: Explore raster metadata<a class="anchor" ar
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">Show me the solution</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb30">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -5952,7 +5960,7 @@ <h3 class="callout-title">Challenge: Explore CHM Raster Values<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb10">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png b/fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png
index 7fdee4e5..823b8ef6 100644
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diff --git a/images.html b/images.html
index b58e0405..3ae2f448 100644
--- a/images.html
+++ b/images.html
@@ -451,14 +451,9 @@ <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-8">Figure 8</h3>
 the legend.
 </figcaption></figure><hr>
 <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-9">Figure 9</h3>
-<p aria-hidden="true">Image 1 of 1: ‘Map of the mobility network in Delft using a different color palette.’</p>
-<figure style="text-align: center"><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><hr>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
 <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-10">Figure 10</h3>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
-<h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-11">Figure 11</h3>
-<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr></section><section id="11-plot-multiple-shape-files"><h2 class="section-heading"><a href="11-plot-multiple-shape-files.html">Plot multiple shapefiles</a></h2>
+<figure><img src="fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr></section><section id="11-plot-multiple-shape-files"><h2 class="section-heading"><a href="11-plot-multiple-shape-files.html">Plot multiple shapefiles</a></h2>
 <hr class="half-width">
 <h3 id="11-plot-multiple-shape-files-figure-1">Figure 1</h3>
 <figure><img src="fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
diff --git a/index.html b/index.html
index 1f299c42..2b542259 100644
--- a/index.html
+++ b/index.html
@@ -405,7 +405,7 @@ <h3 class="callout-title">GDAL, GEOS, and PROJ.4<a class="anchor" aria-label="an
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Windows</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <p>To install the geospatial libraries, install the latest version <a href="https://cran.r-project.org/bin/windows/Rtools/" class="external-link">RTools</a></p>
 </div>
@@ -417,7 +417,7 @@ <h4 class="accordion-header" id="headingSolution1">Windows</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">MacOS</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
 <div class="accordion-body">
 <p>Install the geospatial libraries individually using <a href="https://brew.sh" class="external-link">homebrew</a>. Open Terminal.app and run the
 following commands:</p>
@@ -438,7 +438,7 @@ <h3 class="code-label">BASH<i aria-hidden="true" data-feather="chevron-left"></i
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution3" aria-expanded="false" aria-controls="collapseSolution3">
   <h4 class="accordion-header" id="headingSolution3">Linux</h4>
 </button>
-<div id="collapseSolution3" class="accordion-collapse collapse" aria-labelledby="headingSolution3" data-bs-parent="#accordionSolution3">
+<div id="collapseSolution3" class="accordion-collapse collapse" data-bs-parent="#accordionSolution3" aria-labelledby="headingSolution3">
 <div class="accordion-body">
 <p>Steps for installing the geospatial libraries will vary based on
 which form of Linux you are using. These instructions are adapted from
@@ -494,7 +494,7 @@ <h3 class="callout-title">UDUNITS<a class="anchor" aria-label="anchor" href="#ud
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution4" aria-expanded="false" aria-controls="collapseSolution4">
   <h4 class="accordion-header" id="headingSolution4">Linux</h4>
 </button>
-<div id="collapseSolution4" class="accordion-collapse collapse" aria-labelledby="headingSolution4" data-bs-parent="#accordionSolution4">
+<div id="collapseSolution4" class="accordion-collapse collapse" data-bs-parent="#accordionSolution4" aria-labelledby="headingSolution4">
 <div class="accordion-body">
 <p>Steps for installing the geospatial will vary based on which form of
 Linux you are using. These instructions are adapted from the <a href="https://github.com/r-spatial/sf" class="external-link"><code>sf</code> package’s
@@ -545,7 +545,7 @@ <h3 class="callout-title">R<a class="anchor" aria-label="anchor" href="#r"></a>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution5" aria-expanded="false" aria-controls="collapseSolution5">
   <h4 class="accordion-header" id="headingSolution5">Windows</h4>
 </button>
-<div id="collapseSolution5" class="accordion-collapse collapse" aria-labelledby="headingSolution5" data-bs-parent="#accordionSolution5">
+<div id="collapseSolution5" class="accordion-collapse collapse" data-bs-parent="#accordionSolution5" aria-labelledby="headingSolution5">
 <div class="accordion-body">
 <p>To install <code>R</code>, Windows users should select “Download R
 for Windows” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
@@ -562,7 +562,7 @@ <h4 class="accordion-header" id="headingSolution5">Windows</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution6" aria-expanded="false" aria-controls="collapseSolution6">
   <h4 class="accordion-header" id="headingSolution6">MacOS</h4>
 </button>
-<div id="collapseSolution6" class="accordion-collapse collapse" aria-labelledby="headingSolution6" data-bs-parent="#accordionSolution6">
+<div id="collapseSolution6" class="accordion-collapse collapse" data-bs-parent="#accordionSolution6" aria-labelledby="headingSolution6">
 <div class="accordion-body">
 <p>To install <code>R</code>, macOS users should select “Download R for
 macOS” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
@@ -580,7 +580,7 @@ <h4 class="accordion-header" id="headingSolution6">MacOS</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution7" aria-expanded="false" aria-controls="collapseSolution7">
   <h4 class="accordion-header" id="headingSolution7">Linux</h4>
 </button>
-<div id="collapseSolution7" class="accordion-collapse collapse" aria-labelledby="headingSolution7" data-bs-parent="#accordionSolution7">
+<div id="collapseSolution7" class="accordion-collapse collapse" data-bs-parent="#accordionSolution7" aria-labelledby="headingSolution7">
 <div class="accordion-body">
 <p>To install <code>R</code>, Linux users should select “Download R for
 Linux” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
diff --git a/instructor/01-intro-to-r.html b/instructor/01-intro-to-r.html
index 1cbf589c..047c12fc 100644
--- a/instructor/01-intro-to-r.html
+++ b/instructor/01-intro-to-r.html
@@ -440,7 +440,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
   <h3 class="accordion-header" id="headingInstructor1">
 <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div>Instructor Note</h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
 <div class="accordion-body">
 <p>In interest of time, focus on one way of creating the folders. You
 can showcase an alternative method with just one example.</p>
diff --git a/instructor/02-data-structures.html b/instructor/02-data-structures.html
index 16b1b657..e299fea8 100644
--- a/instructor/02-data-structures.html
+++ b/instructor/02-data-structures.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 12%" class="percentage">
-    12%
+<aside class="col-md-12 lesson-progress"><div style="width: 13%" class="percentage">
+    13%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 12%" aria-valuenow="12" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 13%" aria-valuenow="13" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/instructor/03-explore-data.html b/instructor/03-explore-data.html
index ddd40b5c..f6c530ce 100644
--- a/instructor/03-explore-data.html
+++ b/instructor/03-explore-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 15%" class="percentage">
-    15%
+<aside class="col-md-12 lesson-progress"><div style="width: 16%" class="percentage">
+    16%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 15%" aria-valuenow="15" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 16%" aria-valuenow="16" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/instructor/04-intro-to-visualisation.html b/instructor/04-intro-to-visualisation.html
index c4d21b54..13bebf36 100644
--- a/instructor/04-intro-to-visualisation.html
+++ b/instructor/04-intro-to-visualisation.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 18%" class="percentage">
-    18%
+<aside class="col-md-12 lesson-progress"><div style="width: 19%" class="percentage">
+    19%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 18%" aria-valuenow="18" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 19%" aria-valuenow="19" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/instructor/09-open-and-plot-vector-layers.html b/instructor/09-open-and-plot-vector-layers.html
index e8277b20..26ab023c 100644
--- a/instructor/09-open-and-plot-vector-layers.html
+++ b/instructor/09-open-and-plot-vector-layers.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 20%" class="percentage">
-    20%
+<aside class="col-md-12 lesson-progress"><div style="width: 22%" class="percentage">
+    22%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 20%" aria-valuenow="20" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 22%" aria-valuenow="22" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -362,8 +362,8 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
-<ul><li>Know the difference between point, line, and polygon vector
-data.</li>
+<p>After completing this episode, participants should be able to…</p>
+<ul><li>Differentiate between point, line, and polygon vector data.</li>
 <li>Load vector data into R.</li>
 <li>Access the attributes of a vector object in R.</li>
 </ul></div>
@@ -377,14 +377,14 @@ <h3 class="card-title">Objectives</h3>
   <h3 class="accordion-header" id="headingInstructor1">
 <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div>Instructor Note</h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Make sure that the <code>sf</code> package and its dependencies are
-installed before the workshop. The installation can take quite some
-time, so allocate enough extra time before the workshop for solving
-installation problems. We recommend one or two installation ‘walk-in’
-hours on a day before the workshop and 15-30 minutes at the beginning of
-the first workshop day should be enough to tackle installation
+installed before the workshop. The installation can be lengthy, so
+allocate enough extra time before the workshop for solving installation
+problems. We recommend one or two installation ‘walk-in’ hours on a day
+before the workshop. Also, 15-30 minutes at the beginning of the first
+workshop day should be enough to tackle last-minute installation
 issues.</p>
 </div>
 </div>
@@ -398,25 +398,23 @@ <h3 class="accordion-header" id="headingInstructor1">
 <h3 class="callout-title">Prerequisite<a class="anchor" aria-label="anchor" href="#prereq1"></a>
 </h3>
 <div class="callout-content">
-<p>If you have not installed the <code>sf</code> package yet, run
-<code>install.packages("sf")</code> first. Note that the <code>sf</code>
-package has some external dependencies, namely GEOS, PROJ.4, GDAL and
-UDUNITS, which need to be installed beforehand. Follow the workshop <a href="">setup instructions</a> for the installation of <code>sf</code>
-and its dependencies.</p>
+<p>In this lesson you will work with the <code>sf</code> package. Note
+that the <code>sf</code> package has some external dependencies, namely
+GEOS, PROJ.4, GDAL and UDUNITS, which need to be installed beforehand.
+Before starting the lesson, follow the workshop <a href="index.html#setup">setup instructions</a> for the installation of
+<code>sf</code> and its dependencies.</p>
 </div>
 </div>
 </div>
 <p>First we need to load the packages we will use in this lesson. We
-will use the packages <code>tidyverse</code> and <code>here</code> with
-which you are already familiar from the previous lesson. In addition, we
-need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
+will use the <code>tidyverse</code> package with which you are already
+familiar from the previous lesson. In addition, we need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
 working with spatial vector data.</p>
 <div class="codewrapper sourceCode" id="cb1">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># tools for wrangling, reshaping and visualizing data</span></span>
-<span><span class="kw">library</span><span class="op">(</span><span class="va">here</span><span class="op">)</span>       <span class="co"># managing paths</span></span>
+<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># wrangle, reshape and visualize data</span></span>
 <span><span class="kw">library</span><span class="op">(</span><span class="va">sf</span><span class="op">)</span>         <span class="co"># work with spatial vector data</span></span></code></pre>
 </div>
 <div id="the-sf-package" class="callout callout">
@@ -429,23 +427,25 @@ <h3 class="callout-title">The<code>sf</code>package<a class="anchor" aria-label=
 <div class="callout-content">
 <p><code>sf</code> stands for Simple Features which is a standard
 defined by the Open Geospatial Consortium for storing and accessing
-geospatial vector data. PostGIS uses the same standard; so those of you
-who used PostGIS, might find some resemblances with the functions used
-by the <code>sf</code> package.</p>
+geospatial vector data. PostGIS, for instance, uses the same standard,
+so PostGIS users might recognise the functions used by the
+<code>sf</code> package.</p>
 </div>
 </div>
 </div>
 <section id="import-shapefiles"><h2 class="section-heading">Import shapefiles<a class="anchor" aria-label="anchor" href="#import-shapefiles"></a>
 </h2>
-<hr class="half-width"><p>Let’s start by opening a shapefile. Shapefiles a common file format
-to store spatial vector data used in GIS software. We will read a
-shapefile with the administrative boundary of Delft with the function
+<hr class="half-width"><p>Let’s start by opening a shapefile. Shapefiles are a common file
+format to store spatial vector data used in GIS software. Note that a
+shapefile consists of multiple files and it is important to keep them
+all together in the same location. We will read a shapefile with the
+administrative boundary of Delft with the function
 <code>st_read()</code> from the <code>sf</code> package.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span>, quiet <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="all-sf-functions-start-with-st_" class="callout callout">
 <div class="callout-square">
@@ -457,21 +457,24 @@ <h3 class="callout-title">All<code>sf</code>functions start with<code>st_</code>
 <div class="callout-content">
 <p>Note that all functions from the <code>sf</code> package start with
 the standard prefix <code>st_</code> which stands for Spatial Type. This
-is helpful in at least two ways: (1) it makes the interaction with or
-translation to/from software using the simple features standard like
-PostGIS easy, and (2) it allows for easy autocompletion of function
-names in RStudio.</p>
-</div>
+is helpful in at least two ways:</p>
+<ol style="list-style-type: decimal"><li>it allows for easy autocompletion of function names in RStudio,
+and</li>
+<li>it makes the interaction with or translation to/from software using
+the simple features standard like PostGIS easy.</li>
+</ol></div>
 </div>
 </div>
 </section><section id="spatial-metadata"><h2 class="section-heading">Spatial Metadata<a class="anchor" aria-label="anchor" href="#spatial-metadata"></a>
 </h2>
-<hr class="half-width"><p>The <code>st_read()</code> function gave us a message with a summary
-of metadata about the file that was read in. To examine the metadata in
+<hr class="half-width"><p>By default (with <code>quiet = FALSE</code>), the
+<code>st_read()</code> function provides a message with a summary of
+metadata about the file that was read in. To examine the metadata in
 more detail, we can use other, more specialised, functions from the
-<code>sf</code> package. The <code>st_geometry_type()</code> function,
-for instance, gives us information about the geometry type, which in
-this case is <code>POLYGON</code>.</p>
+<code>sf</code> package.</p>
+<p>The <code>st_geometry_type()</code> function, for instance, gives us
+information about the geometry type, which in this case is
+<code>POLYGON</code>.</p>
 <div class="codewrapper sourceCode" id="cb3">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -486,7 +489,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </div>
 <p>The <code>st_crs()</code> function returns the coordinate reference
 system (CRS) used by the shapefile, which in this case is
-<code>WGS84</code> and has the unique reference code
+<code>WGS 84</code> and has the unique reference code
 <code>EPSG: 4326</code>.</p>
 <div class="codewrapper sourceCode" id="cb5">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -530,7 +533,7 @@ <h3 class="callout-title">Examining the output of<code>st_crs()</code><a class="
 </div>
 </div>
 <p>The <code>st_bbox()</code> function shows the extent of the layer. As
-<code>WGS84</code> is a <strong>geographic CRS</strong>, the extent of
+<code>WGS 84</code> is a <strong>geographic CRS</strong>, the extent of
 the shapefile is displayed in degrees.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -549,62 +552,34 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 our shapefile, we will use the <code>st_transform()</code> function. For
 the <code>crs</code> argument we can use the EPSG code of the CRS we
 want to use, which is <code>28992</code> for the
-<code>Amersfort / RD New</code> projection.</p>
+<code>Amersfort / RD New</code> projection. To check the EPSG code of
+any CRS, we can check this website: <a href="https://epsg.io/" class="external-link uri">https://epsg.io/</a></p>
 <div class="codewrapper sourceCode" id="cb9">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_transform</span><span class="op">(</span><span class="va">boundary_Delft</span>, <span class="fl">28992</span><span class="op">)</span></span>
-<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span></span></code></pre>
+<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">Name</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>Coordinate Reference System:
-  User input: EPSG:28992 
-  wkt:
-PROJCRS["Amersfoort / RD New",
-    BASEGEOGCRS["Amersfoort",
-        DATUM["Amersfoort",
-            ELLIPSOID["Bessel 1841",6377397.155,299.1528128,
-                LENGTHUNIT["metre",1]]],
-        PRIMEM["Greenwich",0,
-            ANGLEUNIT["degree",0.0174532925199433]],
-        ID["EPSG",4289]],
-    CONVERSION["RD New",
-        METHOD["Oblique Stereographic",
-            ID["EPSG",9809]],
-        PARAMETER["Latitude of natural origin",52.1561605555556,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8801]],
-        PARAMETER["Longitude of natural origin",5.38763888888889,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8802]],
-        PARAMETER["Scale factor at natural origin",0.9999079,
-            SCALEUNIT["unity",1],
-            ID["EPSG",8805]],
-        PARAMETER["False easting",155000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8806]],
-        PARAMETER["False northing",463000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8807]]],
-    CS[Cartesian,2],
-        AXIS["easting (X)",east,
-            ORDER[1],
-            LENGTHUNIT["metre",1]],
-        AXIS["northing (Y)",north,
-            ORDER[2],
-            LENGTHUNIT["metre",1]],
-    USAGE[
-        SCOPE["Engineering survey, topographic mapping."],
-        AREA["Netherlands - onshore, including Waddenzee, Dutch Wadden Islands and 12-mile offshore coastal zone."],
-        BBOX[50.75,3.2,53.7,7.22]],
-    ID["EPSG",28992]]</code></pre>
+<pre class="output" tabindex="0"><code>[1] "Amersfoort / RD New"</code></pre>
+</div>
+<div class="codewrapper sourceCode" id="cb11">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
 <p>Notice that the bounding box is measured in meters after the
 transformation.</p>
-<div class="codewrapper sourceCode" id="cb11">
+<div class="codewrapper sourceCode" id="cb13">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -616,9 +591,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81743.00 442446.21  87703.78 449847.95 </code></pre>
 </div>
+<div class="codewrapper sourceCode" id="cb15">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">units_gdal</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] "metre"</code></pre>
+</div>
 <p>We confirm the transformation by examining the reprojected
 shapefile.</p>
-<div class="codewrapper sourceCode" id="cb13">
+<div class="codewrapper sourceCode" id="cb17">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -643,19 +629,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#callout4"></a>
 </h3>
 <div class="callout-content">
-<p>More about CRS in <a href="">Handling Spatial Projection &amp;
-CRS</a>.</p>
+<p>Read more about Coordinate Reference Systems <a href="https://datacarpentry.org/organization-geospatial/03-crs.html" class="external-link">here</a>.
+We will also practice transformation between CRS in <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial
+Projection &amp; CRS</a>.</p>
 </div>
 </div>
 </div>
 </section><section id="plot-a-vector-layer"><h2 class="section-heading">Plot a vector layer<a class="anchor" aria-label="anchor" href="#plot-a-vector-layer"></a>
 </h2>
 <hr class="half-width"><p>Now, let’s plot this shapefile. You are already familiar with the
-<code>ggplot2</code> package from <a href="">Introduction to
-Visualisation</a>. <code>ggplot2</code> has special <code>geom_</code>
-functions for spatial data. We will use the <code>geom_sf()</code>
-function for <code>sf</code> data.</p>
-<div class="codewrapper sourceCode" id="cb15">
+<code>ggplot2</code> package from <a href="04-intro-to-visualisation.html">Introduction to Visualisation</a>.
+<code>ggplot2</code> has special <code>geom_</code> functions for
+spatial data. We will use the <code>geom_sf()</code> function for
+<code>sf</code> data.</p>
+<div class="codewrapper sourceCode" id="cb19">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -664,18 +651,18 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Delft Administrative Boundary"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span>  <span class="co"># this is needed to display the axes in meters</span></span></code></pre>
 </div>
-<figure><img src="../fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-1-import-line-and-point-vector-layers" class="callout challenge">
+<figure><img src="../fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-import-line-and-point-vector-layers" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="challenge-1-import-line-and-point-vector-layers" class="callout-inner">
-<h3 class="callout-title">Challenge 1: Import line and point vector
-layers<a class="anchor" aria-label="anchor" href="#challenge-1-import-line-and-point-vector-layers"></a>
+<div id="challenge-import-line-and-point-vector-layers" class="callout-inner">
+<h3 class="callout-title">Challenge: Import line and point vector
+layers<a class="anchor" aria-label="anchor" href="#challenge-import-line-and-point-vector-layers"></a>
 </h3>
 <div class="callout-content">
 <p>Read in <code>delft-streets.shp</code> and
 <code>delft-leisure.shp</code> and assign them to
-<code>lines_Delft</code> and <code>point_Delft</code> respectively.
+<code>lines_Delft</code> and <code>points_Delft</code> respectively.
 Answer the following questions:</p>
 <ol style="list-style-type: decimal"><li>What type of R spatial object is created when you import each
 layer?</li>
@@ -690,44 +677,47 @@ <h3 class="callout-title">Challenge 1: Import line and point vector
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
-<div class="codewrapper sourceCode" id="cb16">
+<div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">lines_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-streets.shp"</span><span class="op">)</span></span>
-<span><span class="va">point_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
+<span><span class="va">points_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
 </div>
-<p>We can check the type of data with the <code>class()</code> function
-from base R. Both <code>lines_Delft</code> and <code>point_Delft</code>
-are objects of class <code>"sf"</code>, which extends the
-<code>"data.frame"</code> class.</p>
-<div class="codewrapper sourceCode" id="cb17">
+<p>We can check the type of type of geometry with the
+<code>st_geometry_type()</code> function. <code>lines_Delft</code>
+contains <code>"LINESTRING"</code> geometry and
+<code>points_Delft</code> is made of <code>"POINT"</code>
+geometries.</p>
+<div class="codewrapper sourceCode" id="cb21">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">1</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] LINESTRING
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb19">
+<div class="codewrapper sourceCode" id="cb23">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">2</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] POINT
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<p><code>lines_Delft</code> and <code>point_Delft</code> are in the
+<p><code>lines_Delft</code> and <code>points_Delft</code> are in the
 correct CRS.</p>
-<div class="codewrapper sourceCode" id="cb21">
+<div class="codewrapper sourceCode" id="cb25">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -738,11 +728,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb23">
+<div class="codewrapper sourceCode" id="cb27">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -752,8 +742,8 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <p>When looking at the bounding boxes with the <code>st_bbox()</code>
 function, we see the spatial extent of the two objects in a projected
 CRS using meters as units. <code>lines_Delft()</code> and
-<code>point_Delft</code> have similar extents.</p>
-<div class="codewrapper sourceCode" id="cb25">
+<code>points_Delft</code> have similar extents.</p>
+<div class="codewrapper sourceCode" id="cb29">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -765,11 +755,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81759.58 441223.13  89081.41 449845.81 </code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb27">
+<div class="codewrapper sourceCode" id="cb31">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -793,7 +783,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul></div>
diff --git a/instructor/10-explore-and-plot-by-vector-layer-attributes.html b/instructor/10-explore-and-plot-by-vector-layer-attributes.html
index 0d17f189..a3c6e187 100644
--- a/instructor/10-explore-and-plot-by-vector-layer-attributes.html
+++ b/instructor/10-explore-and-plot-by-vector-layer-attributes.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 28%" class="percentage">
-    28%
+<aside class="col-md-12 lesson-progress"><div style="width: 30%" class="percentage">
+    30%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 28%" aria-valuenow="28" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 30%" aria-valuenow="30" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -329,7 +329,7 @@ <h1>Explore and plot by vector layer attributes</h1>
         
         
         
-        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 30 minutes</p>
+        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 50 minutes</p>
         
         <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
@@ -352,6 +352,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li><p>Query attributes of a vector object.</p></li>
 <li><p>Subset vector objects using specific attribute values.</p></li>
 <li><p>Plot a vector feature, colored by unique attribute
@@ -439,13 +440,13 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </div>
 </div>
 <p>We can also preview the content of the object by looking at the first
-6 rows with the <code>head()</code> function, which is in the case of an
-<code>sf</code> object the same as examining the object directly.</p>
+6 rows with the <code>head()</code> function, which in the case of an
+<code>sf</code> object is similar to examining the object directly.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span> <span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -531,6 +532,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 [21] "tertiary"       "tertiary_link"  "track"          "trunk"         
 [25] "trunk_link"     "unclassified"  </code></pre>
 </div>
+<p>Note that this way the values are shown by default in alphabetical
+order and <code>NA</code>s are not displayed, whereas using
+<code>unique()</code> returns unique values in the order of their
+occurrence in the data frame and it also shows <code>NA</code>
+values.</p>
 </div>
 </div>
 </div>
@@ -637,7 +643,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="co"># point_Delft</span></span></code></pre>
 </div>
-<p>However, this is not a good approach as the first rows might still
+<p>We have our answer (<code>sports_centre</code> is the third value),
+but in general this is not a good approach as the first rows might still
 have many <code>NA</code>s and three distinct values might still not be
 present in the first <code>n</code> rows of the data frame. To remove
 <code>NA</code>s, we can use the function <code>na.omit()</code> on the
@@ -656,19 +663,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] "picnic_table"  "marina"        "marina"        "sports_centre"
 [5] "sports_centre" "playground"   </code></pre>
 </div>
-<p>To show only unique values, we can use the <code>unique()</code>
-function to only see the first occurrence of each distinct value (note
-that <code>NA</code> will still be included once).</p>
+<p>To show only unique values, we can use the <code>levels()</code>
+function on a factor to only see the first occurrence of each distinct
+value. Note <code>NA</code>s are dropped in this case and that we get
+the first three of the unique alphabetically ordered values.</p>
 <div class="codewrapper sourceCode" id="cb24">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">unique</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">levels</span><span class="op">(</span><span class="fu">factor</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "picnic_table" "marina"       NA            </code></pre>
+<pre class="output" tabindex="0"><code>[1] "dance"       "dog_park"    "escape_game"</code></pre>
 </div>
 <ol start="3" style="list-style-type: decimal"><li>To see a list of all attribute names, we can use the
 <code>names()</code> function.</li>
@@ -768,6 +776,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 </h3>
 <div class="callout-content">
 <!-- 7 minutes -->
+<p>Challenge: Now with motorways (and pedestrian streets)</p>
 <ol style="list-style-type: decimal"><li>Create a new object that only contains the motorways in Delft.</li>
 <li>How many features does the new object have?</li>
 <li>What is the total length of motorways?</li>
@@ -857,7 +866,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 48</code></pre>
 </div>
-<ol start="4" style="list-style-type: decimal"><li>Plot the motorways</li>
+<ol start="4" style="list-style-type: decimal"><li>Plot the motorways.</li>
 </ol><div class="codewrapper sourceCode" id="cb43">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -867,7 +876,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Fast mobility network"</span>, subtitle <span class="op">=</span> <span class="st">"Motorways"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal"><li>Same steps with pedestrian streets</li>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal"><li>Follow the same steps with pedestrian streets.</li>
 </ol><div class="codewrapper sourceCode" id="cb44">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -943,8 +952,10 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 expression in which we only filter the rows of our data frame that have
 one of the four given values <code>"motorway"</code>,
 <code>"primary"</code>, <code>"secondary"</code>, and
-<code>"cycleway"</code>. We also make sure that the highway column is a
-factor column.</p>
+<code>"cycleway"</code>. Note that we do this with the <code>%in</code>
+operator which is a more compact equivalent of a series of conditions
+joined by the <code>|</code> (or) operator. We also make sure that the
+highway column is a factor column.</p>
 <div class="codewrapper sourceCode" id="cb51">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -958,7 +969,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <p>Next we define the four colors we want to use, one for each type of
 road in our vector object. Note that in R you can use named colors like
 <code>"blue"</code>, <code>"green"</code>, <code>"navy"</code>, and
-<code>"purple"</code>. A full list of named colors can be listed with
+<code>"purple"</code>. If you are using RStudio, you will see the named
+colors previewed in line. A full list of named colors can be listed with
 the <code>colors()</code> function.</p>
 <div class="codewrapper sourceCode" id="cb52">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1008,12 +1020,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">scale_linewidth_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">line_widths</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-line-width-by-attribute" class="callout challenge">
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-line-width-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-line-width-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot line width by attribute<a class="anchor" aria-label="anchor" href="#plot-line-width-by-attribute"></a>
+<div id="challenge-plot-line-width-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot line width by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-line-width-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <p>In the example above, we set the line widths to be 1, 0.75, 0.5, and
@@ -1079,13 +1091,14 @@ <h2 id="add-plot-legend">Add plot legend<a class="anchor" aria-label="anchor" hr
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
+<code class="sourceCode R"><span><span class="va">p1</span> <span class="op">&lt;-</span> <span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
 <span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Default Legend"</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span>
+<span><span class="va">p1</span></span></code></pre>
 </div>
 <figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-34-1.png" alt="Mobility network in Delft using thicker lines than the previous example." class="figure mx-auto d-block"><figcaption>
 Mobility network in Delft using thicker lines than the previous example.
@@ -1093,15 +1106,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
+<code class="sourceCode R"><span><span class="va">p2</span> <span class="op">&lt;-</span> <span class="va">p1</span> <span class="op">+</span></span>
 <span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1112,33 +1119,21 @@ <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left">
 Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
 generated.</code></pre>
 </div>
-<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft with large-font and border around
-the legend.
-</figcaption></figure><div class="codewrapper sourceCode" id="cb63">
+<div class="codewrapper sourceCode" id="cb63">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">new_colors</span> <span class="op">&lt;-</span> <span class="fu">c</span><span class="op">(</span><span class="st">"springgreen"</span>, <span class="st">"blue"</span>, <span class="st">"magenta"</span>, <span class="st">"orange"</span><span class="op">)</span></span>
-<span></span>
-<span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">new_colors</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">p2</span></span></code></pre>
 </div>
-<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><div id="plot-lines-by-attributes" class="callout challenge">
+<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
+Map of the mobility network in Delft with large-font and border around
+the legend.
+</figcaption></figure><div id="challenge-plot-lines-by-attributes" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-lines-by-attributes" class="callout-inner">
-<h3 class="callout-title">Plot lines by attributes<a class="anchor" aria-label="anchor" href="#plot-lines-by-attributes"></a>
+<div id="challenge-plot-lines-by-attributes" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot lines by attributes<a class="anchor" aria-label="anchor" href="#challenge-plot-lines-by-attributes"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -1202,16 +1197,16 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network in Delft"</span>, subtitle <span class="op">=</span> <span class="st">"Roads dedicated to Bikes"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
 </div>
 </div>
 </div>
-<div id="plot-polygon-by-attribute" class="callout challenge">
+<div id="challenge-plot-polygon-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-polygon-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#plot-polygon-by-attribute"></a>
+<div id="challenge-plot-polygon-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-polygon-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -1232,7 +1227,7 @@ <h4 class="accordion-header" id="headingSolution5">Show me the solution</h4>
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="fu">here</span><span class="op">(</span><span class="st">"data"</span>, <span class="st">"nl-gemeenten.shp"</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/nl-gemeenten.shp"</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -1292,7 +1287,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
 </div>
 </div>
 </div>
diff --git a/instructor/11-plot-multiple-shape-files.html b/instructor/11-plot-multiple-shape-files.html
index de57472f..3624464d 100644
--- a/instructor/11-plot-multiple-shape-files.html
+++ b/instructor/11-plot-multiple-shape-files.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 35%" class="percentage">
-    35%
+<aside class="col-md-12 lesson-progress"><div style="width: 43%" class="percentage">
+    43%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 35%" aria-valuenow="35" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 43%" aria-valuenow="43" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -337,7 +337,7 @@ <h1>Plot multiple shapefiles</h1>
         
         
         
-        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 60 minutes</p>
+        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 35 minutes</p>
         
         <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
@@ -361,6 +361,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li>Plot multiple vector layers in the same plot.</li>
 <li>Apply custom symbols to spatial objects in a plot.</li>
 </ul></div>
@@ -368,17 +369,16 @@ <h3 class="card-title">Objectives</h3>
 </div>
 </div>
 </div>
-<p>This episode builds upon the <a href="">previous episode</a> to work
-with vector layers in R and explore how to plot multiple vector
-layers.</p>
+<p>This episode builds upon the <a href="10-explore-and-plot-by-vector-layer-attributes.html">previous
+episode</a> to work with vector layers in R and explore how to plot
+multiple vector layers.</p>
 <section id="load-the-data"><h2 class="section-heading">Load the data<a class="anchor" aria-label="anchor" href="#load-the-data"></a>
 </h2>
-<hr class="half-width"><p>To work with vector data in R, we can use the <code>sf</code>
-library. The <code>terra</code> package also allows us to explore
-metadata using similar commands for both raster and vector files. Make
-sure that you have these packages loaded.</p>
+<hr class="half-width"><p>To work with vector data in R, we use the <code>sf</code> library.
+Make sure that it is loaded.</p>
 <p>We will continue to work with the three ESRI shapefiles that we
-loaded in the <a href="">Open and Plot Vector Layers</a> episode.</p>
+loaded in the <a href="09-open-and-plot-vector-layers.html">Open and
+Plot Vector Layers</a> episode.</p>
 </section><section id="plotting-multiple-vector-layers"><h2 class="section-heading">Plotting Multiple Vector Layers<a class="anchor" aria-label="anchor" href="#plotting-multiple-vector-layers"></a>
 </h2>
 <hr class="half-width"><p>So far we learned how to plot information from a single shapefile and
@@ -403,14 +403,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the symbology (the colors and
-symbols) that we used to create the plot above. For example, it might be
-good if the lines were symbolized as lines. In the previous episode, you
-may have noticed that the default legend behavior for
-<code>geom_sf</code> is to draw a ‘patch’ for each legend entry. If you
-want the legend to draw lines or points, you need to add an instruction
-to the <code>geom_sf</code> call - in this case,
-<code>show.legend = 'line'</code>.</p>
+<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the functions
+<code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code>.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -442,8 +437,15 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-3-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>We notice that there are quite some playgrounds in the residential
 parts of Delft, whereas on campus there is a concentration of picnic
 tables. So that is what our next challenge is about.</p>
-<div class="section level3">
-<h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-label="anchor" href="#challenge-7-5-minutes"></a></h3>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout challenge">
+<div class="callout-square">
+<i class="callout-icon" data-feather="zap"></i>
+</div>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout-inner">
+<h3 class="callout-title">Challenge: Visualising multiple layers with a
+custom legend<a class="anchor" aria-label="anchor" href="#challenge-visualising-multiple-layers-with-a-custom-legend"></a>
+</h3>
+<div class="callout-content">
 <p>Create a map of leisure locations only including
 <code>playground</code> and <code>picnic_table</code>, with each point
 colored by the leisure type. Overlay this layer on top of the
@@ -451,6 +453,16 @@ <h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-lab
 that applies line symbols to lines and point symbols to the points.</p>
 <p>Modify the plot above. Tell R to plot each point, using a different
 symbol of shape value.</p>
+</div>
+</div>
+</div>
+<div id="accordionSolution1" class="accordion challenge-accordion accordion-flush">
+<div class="accordion-item">
+<button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
+  <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
+</button>
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb4">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -494,7 +506,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span>, <span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">leisure_locations_selection</span>, <span class="fu">aes</span><span class="op">(</span>fill <span class="op">=</span> <span class="va">leisure</span><span class="op">)</span>, </span>
-<span>          shape <span class="op">=</span> <span class="fl">21</span>, show.legend <span class="op">=</span> <span class="st">'point'</span><span class="op">)</span> <span class="op">+</span> </span>
+<span>          shape <span class="op">=</span> <span class="fl">21</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Line Type"</span>, values <span class="op">=</span> <span class="va">road_colors</span>,</span>
 <span>     guide <span class="op">=</span> <span class="fu">guide_legend</span><span class="op">(</span>override.aes <span class="op">=</span> <span class="fu">list</span><span class="op">(</span>linetype <span class="op">=</span> <span class="st">"solid"</span>, shape <span class="op">=</span> <span class="cn">NA</span><span class="op">)</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_fill_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Soil Type"</span>, values <span class="op">=</span> <span class="va">blue_orange</span>,</span>
@@ -517,7 +529,11 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Road network and leisure"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><!-- End of challenge --><div id="keypoints1" class="callout keypoints">
+<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure></div>
+</div>
+</div>
+</div>
+<div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
 <i class="callout-icon" data-feather="key"></i>
 </div>
@@ -528,10 +544,8 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <ul><li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul></div>
 </div>
 </div>
@@ -539,7 +553,6 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 Place links that you need to refer to multiple times across pages here. Delete
 any links that you are not going to use. 
  -->
-</div>
 </section></div> <!-- / div.lesson-content -->
     </main><!-- / main#main-content.main-content --><nav class="bottom-pagination mx-md-4" aria-label="Previous and Next Chapter"><div class="d-block d-sm-block d-md-none">
         <a class="chapter-link" href="../instructor/10-explore-and-plot-by-vector-layer-attributes.html"><i aria-hidden="true" class="small-arrow" data-feather="arrow-left"></i>Previous</a>
diff --git a/instructor/12-handling-spatial-projection-and-crs.html b/instructor/12-handling-spatial-projection-and-crs.html
index 77152f86..75000ac4 100644
--- a/instructor/12-handling-spatial-projection-and-crs.html
+++ b/instructor/12-handling-spatial-projection-and-crs.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 49%" class="percentage">
-    49%
+<aside class="col-md-12 lesson-progress"><div style="width: 52%" class="percentage">
+    52%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 49%" aria-valuenow="49" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 52%" aria-valuenow="52" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -337,7 +337,7 @@ <h1>Handling Spatial Projections &amp; CRS</h1>
         
         
         
-        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 60 minutes</p>
+        <p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 30 minutes</p>
         
         <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
@@ -360,6 +360,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul><li>Plot vector objects with different CRSs in the same plot.</li>
 </ul></div>
 </div>
@@ -500,18 +501,20 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Map of Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-multiple-layers-of-spatial-data" class="callout challenge">
+<figure><img src="../fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-multiple-layers-of-spatial-data" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-multiple-layers-of-spatial-data" class="callout-inner">
-<h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor" aria-label="anchor" href="#plot-multiple-layers-of-spatial-data"></a>
+<div id="challenge-plot-multiple-layers-of-spatial-data" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot multiple layers of spatial
+data<a class="anchor" aria-label="anchor" href="#challenge-plot-multiple-layers-of-spatial-data"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
 <p>Create a map of South Holland as follows:</p>
-<ol style="list-style-type: decimal"><li>Import and plot <code>nl-gemeenten.shp</code>. Adjust line width as
-necessary.</li>
+<ol style="list-style-type: decimal"><li>Import <code>nl-gemeenten.shp</code> and filter only the
+municipalities in South Holland.</li>
+<li>Plot it and adjust line width as necessary.</li>
 <li>Layer the boundary of Delft onto the plot.</li>
 <li>Add a title.</li>
 <li>Add a legend that shows both the province boundaries (as a line) and
@@ -524,7 +527,7 @@ <h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb18">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -553,12 +556,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 </section><section id="export-a-shapefile"><h2 class="section-heading">Export a shapefile<a class="anchor" aria-label="anchor" href="#export-a-shapefile"></a>
 </h2>
 <hr class="half-width"><p>To save a file, use the <code>st_write()</code> function from the
-<code>sf</code> package.</p>
+<code>sf</code> package. Although <code>sf</code> guesses the driver
+needed for a specified output file name from its extension, this can be
+made explicitly via the <code>driver</code> argument. In our case
+<code>driver = "ESRI Shapefile"</code> ensures that the output is
+correctly saved as a <code>.shp</code> file.</p>
 <div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="sourceCode r" tabindex="0"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true" tabindex="-1"></a><span class="fu">st_write</span>(leisure_locations_selection,</span>
-<span id="cb20-2"><a href="#cb20-2" aria-hidden="true" tabindex="-1"></a>         <span class="st">"data/leisure_locations_selection.shp"</span>), driver <span class="ot">=</span> <span class="st">"ESRI Shapefile"</span><span class="er">)</span></span></code></pre>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_write</span><span class="op">(</span><span class="va">leisure_locations_selection</span>,</span>
+<span>         <span class="st">"data/leisure_locations_selection.shp"</span>, driver <span class="op">=</span> <span class="st">"ESRI Shapefile"</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
diff --git a/instructor/13-intro-to-raster-data.html b/instructor/13-intro-to-raster-data.html
index a22a6941..a9cb7b9b 100644
--- a/instructor/13-intro-to-raster-data.html
+++ b/instructor/13-intro-to-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 63%" class="percentage">
-    63%
+<aside class="col-md-12 lesson-progress"><div style="width: 60%" class="percentage">
+    60%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 63%" aria-valuenow="63" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 60%" aria-valuenow="60" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -712,7 +712,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <p><code>+units=m</code> in the output of the code above tells us that
 our data is in meters (m).</p>
@@ -895,7 +895,7 @@ <h3 class="callout-title">Challenge: Explore raster metadata<a class="anchor" ar
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">Show me the solution</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb30">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/instructor/14-plot-raster-data.html b/instructor/14-plot-raster-data.html
index 263f6dbe..89f3b552 100644
--- a/instructor/14-plot-raster-data.html
+++ b/instructor/14-plot-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 71%" class="percentage">
-    71%
+<aside class="col-md-12 lesson-progress"><div style="width: 68%" class="percentage">
+    68%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 71%" aria-valuenow="71" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 68%" aria-valuenow="68" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/instructor/15-reproject-raster-data.html b/instructor/15-reproject-raster-data.html
index 987debe2..b51dc74a 100644
--- a/instructor/15-reproject-raster-data.html
+++ b/instructor/15-reproject-raster-data.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 79%" class="percentage">
-    79%
+<aside class="col-md-12 lesson-progress"><div style="width: 77%" class="percentage">
+    77%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 79%" aria-valuenow="79" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 77%" aria-valuenow="77" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
diff --git a/instructor/16-raster-calculations.html b/instructor/16-raster-calculations.html
index 78d9bf78..a5394c64 100644
--- a/instructor/16-raster-calculations.html
+++ b/instructor/16-raster-calculations.html
@@ -86,11 +86,11 @@
   Geospatial Data Carpentry for Urbanism
 </div>
 
-<aside class="col-md-12 lesson-progress"><div style="width: 87%" class="percentage">
-    87%
+<aside class="col-md-12 lesson-progress"><div style="width: 86%" class="percentage">
+    86%
   </div>
   <div class="progress incubator">
-    <div class="progress-bar incubator" role="progressbar" style="width: 87%" aria-valuenow="87" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
+    <div class="progress-bar incubator" role="progressbar" style="width: 86%" aria-valuenow="86" aria-label="Lesson Progress" aria-valuemin="0" aria-valuemax="100">
     </div>
   </div>
 </aside><div class="container">
@@ -627,7 +627,7 @@ <h3 class="callout-title">Challenge: Explore CHM Raster Values<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb10">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/instructor/aio.html b/instructor/aio.html
index f7f79781..8c60aef4 100644
--- a/instructor/aio.html
+++ b/instructor/aio.html
@@ -513,7 +513,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
   <h3 class="accordion-header" id="headingInstructor1">
 <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div>Instructor Note</h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
 <div class="accordion-body">
 <p>In interest of time, focus on one way of creating the folders. You
 can showcase an alternative method with just one example.</p>
@@ -2241,9 +2241,9 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
-<li>Know the difference between point, line, and polygon vector
-data.</li>
+<li>Differentiate between point, line, and polygon vector data.</li>
 <li>Load vector data into R.</li>
 <li>Access the attributes of a vector object in R.</li>
 </ul>
@@ -2258,14 +2258,14 @@ <h3 class="card-title">Objectives</h3>
   <h3 class="accordion-header" id="headingInstructor1">
 <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div>Instructor Note</h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Make sure that the <code>sf</code> package and its dependencies are
-installed before the workshop. The installation can take quite some
-time, so allocate enough extra time before the workshop for solving
-installation problems. We recommend one or two installation ‘walk-in’
-hours on a day before the workshop and 15-30 minutes at the beginning of
-the first workshop day should be enough to tackle installation
+installed before the workshop. The installation can be lengthy, so
+allocate enough extra time before the workshop for solving installation
+problems. We recommend one or two installation ‘walk-in’ hours on a day
+before the workshop. Also, 15-30 minutes at the beginning of the first
+workshop day should be enough to tackle last-minute installation
 issues.</p>
 </div>
 </div>
@@ -2279,25 +2279,23 @@ <h3 class="accordion-header" id="headingInstructor1">
 <h3 class="callout-title">Prerequisite<a class="anchor" aria-label="anchor" href="#prereq1"></a>
 </h3>
 <div class="callout-content">
-<p>If you have not installed the <code>sf</code> package yet, run
-<code>install.packages("sf")</code> first. Note that the <code>sf</code>
-package has some external dependencies, namely GEOS, PROJ.4, GDAL and
-UDUNITS, which need to be installed beforehand. Follow the workshop <a href="">setup instructions</a> for the installation of <code>sf</code>
-and its dependencies.</p>
+<p>In this lesson you will work with the <code>sf</code> package. Note
+that the <code>sf</code> package has some external dependencies, namely
+GEOS, PROJ.4, GDAL and UDUNITS, which need to be installed beforehand.
+Before starting the lesson, follow the workshop <a href="index.html#setup">setup instructions</a> for the installation of
+<code>sf</code> and its dependencies.</p>
 </div>
 </div>
 </div>
 <p>First we need to load the packages we will use in this lesson. We
-will use the packages <code>tidyverse</code> and <code>here</code> with
-which you are already familiar from the previous lesson. In addition, we
-need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
+will use the <code>tidyverse</code> package with which you are already
+familiar from the previous lesson. In addition, we need to load the <a href="https://r-spatial.github.io/sf/" class="external-link"><code>sf</code></a> package for
 working with spatial vector data.</p>
 <div class="codewrapper sourceCode" id="cb1">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># tools for wrangling, reshaping and visualizing data</span></span>
-<span><span class="kw">library</span><span class="op">(</span><span class="va">here</span><span class="op">)</span>       <span class="co"># managing paths</span></span>
+<code class="sourceCode R"><span><span class="kw">library</span><span class="op">(</span><span class="va">tidyverse</span><span class="op">)</span>  <span class="co"># wrangle, reshape and visualize data</span></span>
 <span><span class="kw">library</span><span class="op">(</span><span class="va">sf</span><span class="op">)</span>         <span class="co"># work with spatial vector data</span></span></code></pre>
 </div>
 <div id="the-sf-package" class="callout callout">
@@ -2310,24 +2308,26 @@ <h3 class="callout-title">The<code>sf</code>package<a class="anchor" aria-label=
 <div class="callout-content">
 <p><code>sf</code> stands for Simple Features which is a standard
 defined by the Open Geospatial Consortium for storing and accessing
-geospatial vector data. PostGIS uses the same standard; so those of you
-who used PostGIS, might find some resemblances with the functions used
-by the <code>sf</code> package.</p>
+geospatial vector data. PostGIS, for instance, uses the same standard,
+so PostGIS users might recognise the functions used by the
+<code>sf</code> package.</p>
 </div>
 </div>
 </div>
 <section id="import-shapefiles"><h2 class="section-heading">Import shapefiles<a class="anchor" aria-label="anchor" href="#import-shapefiles"></a>
 </h2>
 <hr class="half-width">
-<p>Let’s start by opening a shapefile. Shapefiles a common file format
-to store spatial vector data used in GIS software. We will read a
-shapefile with the administrative boundary of Delft with the function
+<p>Let’s start by opening a shapefile. Shapefiles are a common file
+format to store spatial vector data used in GIS software. Note that a
+shapefile consists of multiple files and it is important to keep them
+all together in the same location. We will read a shapefile with the
+administrative boundary of Delft with the function
 <code>st_read()</code> from the <code>sf</code> package.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-boundary.shp"</span>, quiet <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="all-sf-functions-start-with-st_" class="callout callout">
 <div class="callout-square">
@@ -2339,22 +2339,27 @@ <h3 class="callout-title">All<code>sf</code>functions start with<code>st_</code>
 <div class="callout-content">
 <p>Note that all functions from the <code>sf</code> package start with
 the standard prefix <code>st_</code> which stands for Spatial Type. This
-is helpful in at least two ways: (1) it makes the interaction with or
-translation to/from software using the simple features standard like
-PostGIS easy, and (2) it allows for easy autocompletion of function
-names in RStudio.</p>
+is helpful in at least two ways:</p>
+<ol style="list-style-type: decimal">
+<li>it allows for easy autocompletion of function names in RStudio,
+and</li>
+<li>it makes the interaction with or translation to/from software using
+the simple features standard like PostGIS easy.</li>
+</ol>
 </div>
 </div>
 </div>
 </section><section id="spatial-metadata"><h2 class="section-heading">Spatial Metadata<a class="anchor" aria-label="anchor" href="#spatial-metadata"></a>
 </h2>
 <hr class="half-width">
-<p>The <code>st_read()</code> function gave us a message with a summary
-of metadata about the file that was read in. To examine the metadata in
+<p>By default (with <code>quiet = FALSE</code>), the
+<code>st_read()</code> function provides a message with a summary of
+metadata about the file that was read in. To examine the metadata in
 more detail, we can use other, more specialised, functions from the
-<code>sf</code> package. The <code>st_geometry_type()</code> function,
-for instance, gives us information about the geometry type, which in
-this case is <code>POLYGON</code>.</p>
+<code>sf</code> package.</p>
+<p>The <code>st_geometry_type()</code> function, for instance, gives us
+information about the geometry type, which in this case is
+<code>POLYGON</code>.</p>
 <div class="codewrapper sourceCode" id="cb3">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -2369,7 +2374,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </div>
 <p>The <code>st_crs()</code> function returns the coordinate reference
 system (CRS) used by the shapefile, which in this case is
-<code>WGS84</code> and has the unique reference code
+<code>WGS 84</code> and has the unique reference code
 <code>EPSG: 4326</code>.</p>
 <div class="codewrapper sourceCode" id="cb5">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2413,7 +2418,7 @@ <h3 class="callout-title">Examining the output of<code>st_crs()</code><a class="
 </div>
 </div>
 <p>The <code>st_bbox()</code> function shows the extent of the layer. As
-<code>WGS84</code> is a <strong>geographic CRS</strong>, the extent of
+<code>WGS 84</code> is a <strong>geographic CRS</strong>, the extent of
 the shapefile is displayed in degrees.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2432,62 +2437,34 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 our shapefile, we will use the <code>st_transform()</code> function. For
 the <code>crs</code> argument we can use the EPSG code of the CRS we
 want to use, which is <code>28992</code> for the
-<code>Amersfort / RD New</code> projection.</p>
+<code>Amersfort / RD New</code> projection. To check the EPSG code of
+any CRS, we can check this website: <a href="https://epsg.io/" class="external-link uri">https://epsg.io/</a></p>
 <div class="codewrapper sourceCode" id="cb9">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">boundary_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_transform</span><span class="op">(</span><span class="va">boundary_Delft</span>, <span class="fl">28992</span><span class="op">)</span></span>
-<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span></span></code></pre>
+<span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">Name</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>Coordinate Reference System:
-  User input: EPSG:28992 
-  wkt:
-PROJCRS["Amersfoort / RD New",
-    BASEGEOGCRS["Amersfoort",
-        DATUM["Amersfoort",
-            ELLIPSOID["Bessel 1841",6377397.155,299.1528128,
-                LENGTHUNIT["metre",1]]],
-        PRIMEM["Greenwich",0,
-            ANGLEUNIT["degree",0.0174532925199433]],
-        ID["EPSG",4289]],
-    CONVERSION["RD New",
-        METHOD["Oblique Stereographic",
-            ID["EPSG",9809]],
-        PARAMETER["Latitude of natural origin",52.1561605555556,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8801]],
-        PARAMETER["Longitude of natural origin",5.38763888888889,
-            ANGLEUNIT["degree",0.0174532925199433],
-            ID["EPSG",8802]],
-        PARAMETER["Scale factor at natural origin",0.9999079,
-            SCALEUNIT["unity",1],
-            ID["EPSG",8805]],
-        PARAMETER["False easting",155000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8806]],
-        PARAMETER["False northing",463000,
-            LENGTHUNIT["metre",1],
-            ID["EPSG",8807]]],
-    CS[Cartesian,2],
-        AXIS["easting (X)",east,
-            ORDER[1],
-            LENGTHUNIT["metre",1]],
-        AXIS["northing (Y)",north,
-            ORDER[2],
-            LENGTHUNIT["metre",1]],
-    USAGE[
-        SCOPE["Engineering survey, topographic mapping."],
-        AREA["Netherlands - onshore, including Waddenzee, Dutch Wadden Islands and 12-mile offshore coastal zone."],
-        BBOX[50.75,3.2,53.7,7.22]],
-    ID["EPSG",28992]]</code></pre>
+<pre class="output" tabindex="0"><code>[1] "Amersfoort / RD New"</code></pre>
+</div>
+<div class="codewrapper sourceCode" id="cb11">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
 <p>Notice that the bounding box is measured in meters after the
 transformation.</p>
-<div class="codewrapper sourceCode" id="cb11">
+<div class="codewrapper sourceCode" id="cb13">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2499,9 +2476,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81743.00 442446.21  87703.78 449847.95 </code></pre>
 </div>
+<div class="codewrapper sourceCode" id="cb15">
+<h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">boundary_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">units_gdal</span></span></code></pre>
+</div>
+<div class="codewrapper">
+<h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
+</h3>
+<pre class="output" tabindex="0"><code>[1] "metre"</code></pre>
+</div>
 <p>We confirm the transformation by examining the reprojected
 shapefile.</p>
-<div class="codewrapper sourceCode" id="cb13">
+<div class="codewrapper sourceCode" id="cb17">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2526,8 +2514,9 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#callout4"></a>
 </h3>
 <div class="callout-content">
-<p>More about CRS in <a href="">Handling Spatial Projection &amp;
-CRS</a>.</p>
+<p>Read more about Coordinate Reference Systems <a href="https://datacarpentry.org/organization-geospatial/03-crs.html" class="external-link">here</a>.
+We will also practice transformation between CRS in <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial
+Projection &amp; CRS</a>.</p>
 </div>
 </div>
 </div>
@@ -2535,11 +2524,11 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </h2>
 <hr class="half-width">
 <p>Now, let’s plot this shapefile. You are already familiar with the
-<code>ggplot2</code> package from <a href="">Introduction to
-Visualisation</a>. <code>ggplot2</code> has special <code>geom_</code>
-functions for spatial data. We will use the <code>geom_sf()</code>
-function for <code>sf</code> data.</p>
-<div class="codewrapper sourceCode" id="cb15">
+<code>ggplot2</code> package from <a href="04-intro-to-visualisation.html">Introduction to Visualisation</a>.
+<code>ggplot2</code> has special <code>geom_</code> functions for
+spatial data. We will use the <code>geom_sf()</code> function for
+<code>sf</code> data.</p>
+<div class="codewrapper sourceCode" id="cb19">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2548,18 +2537,18 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Delft Administrative Boundary"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span>  <span class="co"># this is needed to display the axes in meters</span></span></code></pre>
 </div>
-<figure><img src="../fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-1-import-line-and-point-vector-layers" class="callout challenge">
+<figure><img src="../fig/09-open-and-plot-vector-layers-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-import-line-and-point-vector-layers" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="challenge-1-import-line-and-point-vector-layers" class="callout-inner">
-<h3 class="callout-title">Challenge 1: Import line and point vector
-layers<a class="anchor" aria-label="anchor" href="#challenge-1-import-line-and-point-vector-layers"></a>
+<div id="challenge-import-line-and-point-vector-layers" class="callout-inner">
+<h3 class="callout-title">Challenge: Import line and point vector
+layers<a class="anchor" aria-label="anchor" href="#challenge-import-line-and-point-vector-layers"></a>
 </h3>
 <div class="callout-content">
 <p>Read in <code>delft-streets.shp</code> and
 <code>delft-leisure.shp</code> and assign them to
-<code>lines_Delft</code> and <code>point_Delft</code> respectively.
+<code>lines_Delft</code> and <code>points_Delft</code> respectively.
 Answer the following questions:</p>
 <ol style="list-style-type: decimal">
 <li>What type of R spatial object is created when you import each
@@ -2576,44 +2565,47 @@ <h3 class="callout-title">Challenge 1: Import line and point vector
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
-<div class="codewrapper sourceCode" id="cb16">
+<div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="va">lines_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-streets.shp"</span><span class="op">)</span></span>
-<span><span class="va">point_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
+<span><span class="va">points_Delft</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/delft-leisure.shp"</span><span class="op">)</span></span></code></pre>
 </div>
-<p>We can check the type of data with the <code>class()</code> function
-from base R. Both <code>lines_Delft</code> and <code>point_Delft</code>
-are objects of class <code>"sf"</code>, which extends the
-<code>"data.frame"</code> class.</p>
-<div class="codewrapper sourceCode" id="cb17">
+<p>We can check the type of type of geometry with the
+<code>st_geometry_type()</code> function. <code>lines_Delft</code>
+contains <code>"LINESTRING"</code> geometry and
+<code>points_Delft</code> is made of <code>"POINT"</code>
+geometries.</p>
+<div class="codewrapper sourceCode" id="cb21">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">1</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] LINESTRING
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb19">
+<div class="codewrapper sourceCode" id="cb23">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">class</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_geometry_type</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">[</span><span class="fl">2</span><span class="op">]</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "sf"         "data.frame"</code></pre>
+<pre class="output" tabindex="0"><code>[1] POINT
+18 Levels: GEOMETRY POINT LINESTRING POLYGON MULTIPOINT ... TRIANGLE</code></pre>
 </div>
-<p><code>lines_Delft</code> and <code>point_Delft</code> are in the
+<p><code>lines_Delft</code> and <code>points_Delft</code> are in the
 correct CRS.</p>
-<div class="codewrapper sourceCode" id="cb21">
+<div class="codewrapper sourceCode" id="cb25">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2624,11 +2616,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 </h3>
 <pre class="output" tabindex="0"><code>[1] 28992</code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb23">
+<div class="codewrapper sourceCode" id="cb27">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_crs</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span><span class="op">$</span><span class="va">epsg</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2638,8 +2630,8 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <p>When looking at the bounding boxes with the <code>st_bbox()</code>
 function, we see the spatial extent of the two objects in a projected
 CRS using meters as units. <code>lines_Delft()</code> and
-<code>point_Delft</code> have similar extents.</p>
-<div class="codewrapper sourceCode" id="cb25">
+<code>points_Delft</code> have similar extents.</p>
+<div class="codewrapper sourceCode" id="cb29">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
@@ -2651,11 +2643,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>     xmin      ymin      xmax      ymax 
  81759.58 441223.13  89081.41 449845.81 </code></pre>
 </div>
-<div class="codewrapper sourceCode" id="cb27">
+<div class="codewrapper sourceCode" id="cb31">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">st_bbox</span><span class="op">(</span><span class="va">points_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2680,7 +2672,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul>
@@ -2696,7 +2688,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <p>Last updated on 2024-01-29 |
         
         <a href="https://github.com/carpentries-incubator/r-geospatial-urban/edit/main/episodes/10-explore-and-plot-by-vector-layer-attributes.Rmd" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
-<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 30 minutes</p>
+<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 50 minutes</p>
 <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
         </div>
@@ -2717,6 +2709,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li><p>Query attributes of a vector object.</p></li>
 <li><p>Subset vector objects using specific attribute values.</p></li>
@@ -2807,13 +2800,13 @@ <h3 class="callout-title">Callout<a class="anchor" aria-label="anchor" href="#ca
 </div>
 </div>
 <p>We can also preview the content of the object by looking at the first
-6 rows with the <code>head()</code> function, which is in the case of an
-<code>sf</code> object the same as examining the object directly.</p>
+6 rows with the <code>head()</code> function, which in the case of an
+<code>sf</code> object is similar to examining the object directly.</p>
 <div class="codewrapper sourceCode" id="cb7">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span> <span class="op">(</span><span class="va">lines_Delft</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -2900,6 +2893,11 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 [21] "tertiary"       "tertiary_link"  "track"          "trunk"         
 [25] "trunk_link"     "unclassified"  </code></pre>
 </div>
+<p>Note that this way the values are shown by default in alphabetical
+order and <code>NA</code>s are not displayed, whereas using
+<code>unique()</code> returns unique values in the order of their
+occurrence in the data frame and it also shows <code>NA</code>
+values.</p>
 </div>
 </div>
 </div>
@@ -3014,7 +3012,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <pre class="downlit sourceCode r">
 <code class="sourceCode R"><span><span class="co"># point_Delft</span></span></code></pre>
 </div>
-<p>However, this is not a good approach as the first rows might still
+<p>We have our answer (<code>sports_centre</code> is the third value),
+but in general this is not a good approach as the first rows might still
 have many <code>NA</code>s and three distinct values might still not be
 present in the first <code>n</code> rows of the data frame. To remove
 <code>NA</code>s, we can use the function <code>na.omit()</code> on the
@@ -3033,19 +3032,20 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] "picnic_table"  "marina"        "marina"        "sports_centre"
 [5] "sports_centre" "playground"   </code></pre>
 </div>
-<p>To show only unique values, we can use the <code>unique()</code>
-function to only see the first occurrence of each distinct value (note
-that <code>NA</code> will still be included once).</p>
+<p>To show only unique values, we can use the <code>levels()</code>
+function on a factor to only see the first occurrence of each distinct
+value. Note <code>NA</code>s are dropped in this case and that we get
+the first three of the unique alphabetically ordered values.</p>
 <div class="codewrapper sourceCode" id="cb24">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">unique</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
+<code class="sourceCode R"><span><span class="fu">head</span><span class="op">(</span><span class="fu">levels</span><span class="op">(</span><span class="fu">factor</span><span class="op">(</span><span class="va">point_Delft</span><span class="op">$</span><span class="va">leisure</span><span class="op">)</span><span class="op">)</span>, n <span class="op">=</span> <span class="fl">3</span><span class="op">)</span>   <span class="co"># this is even better</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="output" tabindex="0"><code>[1] "picnic_table" "marina"       NA            </code></pre>
+<pre class="output" tabindex="0"><code>[1] "dance"       "dog_park"    "escape_game"</code></pre>
 </div>
 <ol start="3" style="list-style-type: decimal">
 <li>To see a list of all attribute names, we can use the
@@ -3148,6 +3148,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 </h3>
 <div class="callout-content">
 <!-- 7 minutes -->
+<p>Challenge: Now with motorways (and pedestrian streets)</p>
 <ol style="list-style-type: decimal">
 <li>Create a new object that only contains the motorways in Delft.</li>
 <li>How many features does the new object have?</li>
@@ -3246,7 +3247,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 <pre class="output" tabindex="0"><code>[1] 48</code></pre>
 </div>
 <ol start="4" style="list-style-type: decimal">
-<li>Plot the motorways</li>
+<li>Plot the motorways.</li>
 </ol>
 <div class="codewrapper sourceCode" id="cb43">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3258,7 +3259,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-22-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><ol start="5" style="list-style-type: decimal">
-<li>Same steps with pedestrian streets</li>
+<li>Follow the same steps with pedestrian streets.</li>
 </ol>
 <div class="codewrapper sourceCode" id="cb44">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3337,8 +3338,10 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 expression in which we only filter the rows of our data frame that have
 one of the four given values <code>"motorway"</code>,
 <code>"primary"</code>, <code>"secondary"</code>, and
-<code>"cycleway"</code>. We also make sure that the highway column is a
-factor column.</p>
+<code>"cycleway"</code>. Note that we do this with the <code>%in</code>
+operator which is a more compact equivalent of a series of conditions
+joined by the <code>|</code> (or) operator. We also make sure that the
+highway column is a factor column.</p>
 <div class="codewrapper sourceCode" id="cb51">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3352,7 +3355,8 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <p>Next we define the four colors we want to use, one for each type of
 road in our vector object. Note that in R you can use named colors like
 <code>"blue"</code>, <code>"green"</code>, <code>"navy"</code>, and
-<code>"purple"</code>. A full list of named colors can be listed with
+<code>"purple"</code>. If you are using RStudio, you will see the named
+colors previewed in line. A full list of named colors can be listed with
 the <code>colors()</code> function.</p>
 <div class="codewrapper sourceCode" id="cb52">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3404,12 +3408,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">scale_linewidth_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">line_widths</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-line-width-by-attribute" class="callout challenge">
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-30-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-line-width-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-line-width-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot line width by attribute<a class="anchor" aria-label="anchor" href="#plot-line-width-by-attribute"></a>
+<div id="challenge-plot-line-width-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot line width by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-line-width-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <p>In the example above, we set the line widths to be 1, 0.75, 0.5, and
@@ -3479,13 +3483,14 @@ <h2 id="add-plot-legend">Add plot legend<a class="anchor" aria-label="anchor" hr
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
+<code class="sourceCode R"><span><span class="va">p1</span> <span class="op">&lt;-</span> <span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
 <span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Default Legend"</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span>
+<span><span class="va">p1</span></span></code></pre>
 </div>
 <figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-34-1.png" alt="Mobility network in Delft using thicker lines than the previous example." class="figure mx-auto d-block"><figcaption>
 Mobility network in Delft using thicker lines than the previous example.
@@ -3493,15 +3498,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">road_colors</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
+<code class="sourceCode R"><span><span class="va">p2</span> <span class="op">&lt;-</span> <span class="va">p1</span> <span class="op">+</span></span>
 <span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3512,33 +3511,21 @@ <h3 class="code-label">WARNING<i aria-hidden="true" data-feather="chevron-left">
 Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
 generated.</code></pre>
 </div>
-<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft with large-font and border around
-the legend.
-</figcaption></figure><div class="codewrapper sourceCode" id="cb63">
+<div class="codewrapper sourceCode" id="cb63">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">new_colors</span> <span class="op">&lt;-</span> <span class="fu">c</span><span class="op">(</span><span class="st">"springgreen"</span>, <span class="st">"blue"</span>, <span class="st">"magenta"</span>, <span class="st">"orange"</span><span class="op">)</span></span>
-<span></span>
-<span><span class="fu">ggplot</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">geom_sf</span><span class="op">(</span><span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span>, linewidth <span class="op">=</span> <span class="fl">1.5</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">scale_color_manual</span><span class="op">(</span>values <span class="op">=</span> <span class="va">new_colors</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">labs</span><span class="op">(</span>color <span class="op">=</span> <span class="st">'Road Type'</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">theme</span><span class="op">(</span>legend.text <span class="op">=</span> <span class="fu">element_text</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">20</span><span class="op">)</span>, </span>
-<span>        legend.box.background <span class="op">=</span> <span class="fu">element_rect</span><span class="op">(</span>size <span class="op">=</span> <span class="fl">1</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
-<span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span>, </span>
-<span>       subtitle <span class="op">=</span> <span class="st">"Roads &amp; Cycleways - Modified Legend"</span><span class="op">)</span> <span class="op">+</span></span>
-<span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">p2</span></span></code></pre>
 </div>
-<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><div id="plot-lines-by-attributes" class="callout challenge">
+<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-35-1.png" alt="Map of the mobility network in Delft with large-font and border around the legend." class="figure mx-auto d-block"><figcaption>
+Map of the mobility network in Delft with large-font and border around
+the legend.
+</figcaption></figure><div id="challenge-plot-lines-by-attributes" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-lines-by-attributes" class="callout-inner">
-<h3 class="callout-title">Plot lines by attributes<a class="anchor" aria-label="anchor" href="#plot-lines-by-attributes"></a>
+<div id="challenge-plot-lines-by-attributes" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot lines by attributes<a class="anchor" aria-label="anchor" href="#challenge-plot-lines-by-attributes"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -3602,17 +3589,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network in Delft"</span>, subtitle <span class="op">=</span> <span class="st">"Roads dedicated to Bikes"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
 </div>
 </div>
 </div>
 </div>
-<div id="plot-polygon-by-attribute" class="callout challenge">
+<div id="challenge-plot-polygon-by-attribute" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-polygon-by-attribute" class="callout-inner">
-<h3 class="callout-title">Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#plot-polygon-by-attribute"></a>
+<div id="challenge-plot-polygon-by-attribute" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot polygon by attribute<a class="anchor" aria-label="anchor" href="#challenge-plot-polygon-by-attribute"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
@@ -3633,7 +3620,7 @@ <h4 class="accordion-header" id="headingSolution5">Show me the solution</h4>
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
 <pre class="downlit sourceCode r">
-<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="fu">here</span><span class="op">(</span><span class="st">"data"</span>, <span class="st">"nl-gemeenten.shp"</span><span class="op">)</span><span class="op">)</span></span></code></pre>
+<code class="sourceCode R"><span><span class="va">municipal_boundaries_NL</span> <span class="op">&lt;-</span> <span class="fu">st_read</span><span class="op">(</span><span class="st">"data/nl-gemeenten.shp"</span><span class="op">)</span></span></code></pre>
 </div>
 <div class="codewrapper">
 <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -3693,7 +3680,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
 </div>
 </div>
 </div>
@@ -3725,7 +3712,7 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <p>Last updated on 2024-01-29 |
         
         <a href="https://github.com/carpentries-incubator/r-geospatial-urban/edit/main/episodes/11-plot-multiple-shape-files.Rmd" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
-<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 60 minutes</p>
+<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 35 minutes</p>
 <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
         </div>
@@ -3747,6 +3734,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li>Plot multiple vector layers in the same plot.</li>
 <li>Apply custom symbols to spatial objects in a plot.</li>
@@ -3756,18 +3744,17 @@ <h3 class="card-title">Objectives</h3>
 </div>
 </div>
 </div>
-<p>This episode builds upon the <a href="">previous episode</a> to work
-with vector layers in R and explore how to plot multiple vector
-layers.</p>
+<p>This episode builds upon the <a href="10-explore-and-plot-by-vector-layer-attributes.html">previous
+episode</a> to work with vector layers in R and explore how to plot
+multiple vector layers.</p>
 <section id="load-the-data"><h2 class="section-heading">Load the data<a class="anchor" aria-label="anchor" href="#load-the-data"></a>
 </h2>
 <hr class="half-width">
-<p>To work with vector data in R, we can use the <code>sf</code>
-library. The <code>terra</code> package also allows us to explore
-metadata using similar commands for both raster and vector files. Make
-sure that you have these packages loaded.</p>
+<p>To work with vector data in R, we use the <code>sf</code> library.
+Make sure that it is loaded.</p>
 <p>We will continue to work with the three ESRI shapefiles that we
-loaded in the <a href="">Open and Plot Vector Layers</a> episode.</p>
+loaded in the <a href="09-open-and-plot-vector-layers.html">Open and
+Plot Vector Layers</a> episode.</p>
 </section><section id="plotting-multiple-vector-layers"><h2 class="section-heading">Plotting Multiple Vector Layers<a class="anchor" aria-label="anchor" href="#plotting-multiple-vector-layers"></a>
 </h2>
 <hr class="half-width">
@@ -3793,14 +3780,9 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Mobility network of Delft"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the symbology (the colors and
-symbols) that we used to create the plot above. For example, it might be
-good if the lines were symbolized as lines. In the previous episode, you
-may have noticed that the default legend behavior for
-<code>geom_sf</code> is to draw a ‘patch’ for each legend entry. If you
-want the legend to draw lines or points, you need to add an instruction
-to the <code>geom_sf</code> call - in this case,
-<code>show.legend = 'line'</code>.</p>
+<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>Next, let’s build a custom legend using the functions
+<code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code>.</p>
 <div class="codewrapper sourceCode" id="cb2">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3832,9 +3814,15 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-3-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><p>We notice that there are quite some playgrounds in the residential
 parts of Delft, whereas on campus there is a concentration of picnic
 tables. So that is what our next challenge is about.</p>
-<div class="section level3">
-<h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-label="anchor" href="#challenge-7-5-minutes"></a>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout challenge">
+<div class="callout-square">
+<i class="callout-icon" data-feather="zap"></i>
+</div>
+<div id="challenge-visualising-multiple-layers-with-a-custom-legend" class="callout-inner">
+<h3 class="callout-title">Challenge: Visualising multiple layers with a
+custom legend<a class="anchor" aria-label="anchor" href="#challenge-visualising-multiple-layers-with-a-custom-legend"></a>
 </h3>
+<div class="callout-content">
 <p>Create a map of leisure locations only including
 <code>playground</code> and <code>picnic_table</code>, with each point
 colored by the leisure type. Overlay this layer on top of the
@@ -3842,6 +3830,16 @@ <h3 id="challenge-7-5-minutes">Challenge 7 (5 minutes)<a class="anchor" aria-lab
 that applies line symbols to lines and point symbols to the points.</p>
 <p>Modify the plot above. Tell R to plot each point, using a different
 symbol of shape value.</p>
+</div>
+</div>
+</div>
+<div id="accordionSolution1" class="accordion challenge-accordion accordion-flush">
+<div class="accordion-item">
+<button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
+  <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
+</button>
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb4">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
@@ -3885,7 +3883,7 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <code class="sourceCode R"><span><span class="fu">ggplot</span><span class="op">(</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">lines_Delft_selection</span>, <span class="fu">aes</span><span class="op">(</span>color <span class="op">=</span> <span class="va">highway</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">geom_sf</span><span class="op">(</span>data <span class="op">=</span> <span class="va">leisure_locations_selection</span>, <span class="fu">aes</span><span class="op">(</span>fill <span class="op">=</span> <span class="va">leisure</span><span class="op">)</span>, </span>
-<span>          shape <span class="op">=</span> <span class="fl">21</span>, show.legend <span class="op">=</span> <span class="st">'point'</span><span class="op">)</span> <span class="op">+</span> </span>
+<span>          shape <span class="op">=</span> <span class="fl">21</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_color_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Line Type"</span>, values <span class="op">=</span> <span class="va">road_colors</span>,</span>
 <span>     guide <span class="op">=</span> <span class="fu">guide_legend</span><span class="op">(</span>override.aes <span class="op">=</span> <span class="fu">list</span><span class="op">(</span>linetype <span class="op">=</span> <span class="st">"solid"</span>, shape <span class="op">=</span> <span class="cn">NA</span><span class="op">)</span><span class="op">)</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">scale_fill_manual</span><span class="op">(</span>name <span class="op">=</span> <span class="st">"Soil Type"</span>, values <span class="op">=</span> <span class="va">blue_orange</span>,</span>
@@ -3908,7 +3906,12 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Road network and leisure"</span><span class="op">)</span> <span class="op">+</span> </span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><!-- End of challenge --><div id="keypoints1" class="callout keypoints">
+<figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-8-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure>
+</div>
+</div>
+</div>
+</div>
+<div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
 <i class="callout-icon" data-feather="key"></i>
 </div>
@@ -3920,10 +3923,8 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 <li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul>
 </div>
 </div>
@@ -3932,13 +3933,12 @@ <h3 class="callout-title">Key Points<a class="anchor" aria-label="anchor" href="
 Place links that you need to refer to multiple times across pages here. Delete
 any links that you are not going to use. 
  -->
-</div>
 </section></section><section id="aio-12-handling-spatial-projection-and-crs"><p>Content from <a href="12-handling-spatial-projection-and-crs.html">Handling Spatial Projections &amp; CRS</a></p>
 <hr>
 <p>Last updated on 2024-01-29 |
         
         <a href="https://github.com/carpentries-incubator/r-geospatial-urban/edit/main/episodes/12-handling-spatial-projection-and-crs.Rmd" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
-<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 60 minutes</p>
+<p>Estimated time: <i aria-hidden="true" data-feather="clock"></i> 30 minutes</p>
 <div class="text-end">
           <button role="button" aria-pressed="false" tabindex="0" id="expand-code" class="pull-right" data-expand="Expand All Solutions " data-collapse="Collapse All Solutions "> Expand All Solutions <i aria-hidden="true" data-feather="plus"></i></button>
         </div>
@@ -3959,6 +3959,7 @@ <h3 class="card-title">Questions</h3>
 <div class="card-body">
 <div class="inner bordered">
 <h3 class="card-title">Objectives</h3>
+<p>After completing this episode, participants should be able to…</p>
 <ul>
 <li>Plot vector objects with different CRSs in the same plot.</li>
 </ul>
@@ -4102,19 +4103,21 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 <span>  <span class="fu">labs</span><span class="op">(</span>title <span class="op">=</span> <span class="st">"Map of Contiguous NL Municipal Boundaries"</span><span class="op">)</span> <span class="op">+</span></span>
 <span>  <span class="fu">coord_sf</span><span class="op">(</span>datum <span class="op">=</span> <span class="fu">st_crs</span><span class="op">(</span><span class="fl">28992</span><span class="op">)</span><span class="op">)</span></span></code></pre>
 </div>
-<figure><img src="../fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="plot-multiple-layers-of-spatial-data" class="callout challenge">
+<figure><img src="../fig/12-handling-spatial-projection-and-crs-rendered-unnamed-chunk-9-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><div id="challenge-plot-multiple-layers-of-spatial-data" class="callout challenge">
 <div class="callout-square">
 <i class="callout-icon" data-feather="zap"></i>
 </div>
-<div id="plot-multiple-layers-of-spatial-data" class="callout-inner">
-<h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor" aria-label="anchor" href="#plot-multiple-layers-of-spatial-data"></a>
+<div id="challenge-plot-multiple-layers-of-spatial-data" class="callout-inner">
+<h3 class="callout-title">Challenge: Plot multiple layers of spatial
+data<a class="anchor" aria-label="anchor" href="#challenge-plot-multiple-layers-of-spatial-data"></a>
 </h3>
 <div class="callout-content">
 <!-- 5 minutes -->
 <p>Create a map of South Holland as follows:</p>
 <ol style="list-style-type: decimal">
-<li>Import and plot <code>nl-gemeenten.shp</code>. Adjust line width as
-necessary.</li>
+<li>Import <code>nl-gemeenten.shp</code> and filter only the
+municipalities in South Holland.</li>
+<li>Plot it and adjust line width as necessary.</li>
 <li>Layer the boundary of Delft onto the plot.</li>
 <li>Add a title.</li>
 <li>Add a legend that shows both the province boundaries (as a line) and
@@ -4128,7 +4131,7 @@ <h3 class="callout-title">Plot multiple layers of spatial data<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb18">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -4159,12 +4162,17 @@ <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i
 </h2>
 <hr class="half-width">
 <p>To save a file, use the <code>st_write()</code> function from the
-<code>sf</code> package.</p>
+<code>sf</code> package. Although <code>sf</code> guesses the driver
+needed for a specified output file name from its extension, this can be
+made explicitly via the <code>driver</code> argument. In our case
+<code>driver = "ESRI Shapefile"</code> ensures that the output is
+correctly saved as a <code>.shp</code> file.</p>
 <div class="codewrapper sourceCode" id="cb20">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
 </h3>
-<pre class="sourceCode r" tabindex="0"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true" tabindex="-1"></a><span class="fu">st_write</span>(leisure_locations_selection,</span>
-<span id="cb20-2"><a href="#cb20-2" aria-hidden="true" tabindex="-1"></a>         <span class="st">"data/leisure_locations_selection.shp"</span>), driver <span class="ot">=</span> <span class="st">"ESRI Shapefile"</span><span class="er">)</span></span></code></pre>
+<pre class="downlit sourceCode r">
+<code class="sourceCode R"><span><span class="fu">st_write</span><span class="op">(</span><span class="va">leisure_locations_selection</span>,</span>
+<span>         <span class="st">"data/leisure_locations_selection.shp"</span>, driver <span class="op">=</span> <span class="st">"ESRI Shapefile"</span><span class="op">)</span></span></code></pre>
 </div>
 <div id="keypoints1" class="callout keypoints">
 <div class="callout-square">
@@ -4570,7 +4578,7 @@ <h3 class="callout-title">Challenge<a class="anchor" aria-label="anchor" href="#
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <p><code>+units=m</code> in the output of the code above tells us that
 our data is in meters (m).</p>
@@ -4758,7 +4766,7 @@ <h3 class="callout-title">Challenge: Explore raster metadata<a class="anchor" ar
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">Show me the solution</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb30">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
@@ -6003,7 +6011,7 @@ <h3 class="callout-title">Challenge: Explore CHM Raster Values<a class="anchor"
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Show me the solution</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <div class="codewrapper sourceCode" id="cb10">
 <h3 class="code-label">R<i aria-hidden="true" data-feather="chevron-left"></i><i aria-hidden="true" data-feather="chevron-right"></i>
diff --git a/instructor/images.html b/instructor/images.html
index 69d75561..d95db730 100644
--- a/instructor/images.html
+++ b/instructor/images.html
@@ -453,14 +453,9 @@ <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-8">Figure 8</h3>
 the legend.
 </figcaption></figure><hr>
 <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-9">Figure 9</h3>
-<p aria-hidden="true">Image 1 of 1: ‘Map of the mobility network in Delft using a different color palette.’</p>
-<figure style="text-align: center"><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-36-1.png" alt="Map of the mobility network in Delft using a different color palette." class="figure mx-auto d-block"><figcaption>
-Map of the mobility network in Delft using a different color palette.
-</figcaption></figure><hr>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-38-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
 <h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-10">Figure 10</h3>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-39-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
-<h3 id="10-explore-and-plot-by-vector-layer-attributes-figure-11">Figure 11</h3>
-<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-42-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr></section><section id="11-plot-multiple-shape-files"><h2 class="section-heading"><a href="11-plot-multiple-shape-files.html">Plot multiple shapefiles</a></h2>
+<figure><img src="../fig/10-explore-and-plot-by-vector-layer-attributes-rendered-unnamed-chunk-41-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr></section><section id="11-plot-multiple-shape-files"><h2 class="section-heading"><a href="11-plot-multiple-shape-files.html">Plot multiple shapefiles</a></h2>
 <hr class="half-width">
 <h3 id="11-plot-multiple-shape-files-figure-1">Figure 1</h3>
 <figure><img src="../fig/11-plot-multiple-shape-files-rendered-unnamed-chunk-1-1.png" style="display: block; margin: auto;" class="figure mx-auto d-block"></figure><hr>
diff --git a/instructor/index.html b/instructor/index.html
index 66a8619c..ca32fc55 100644
--- a/instructor/index.html
+++ b/instructor/index.html
@@ -397,7 +397,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 How can I examine the attributes of a vector layer?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>02h 26m
+<span class="visually-hidden">Duration: </span>02h 46m
 </td>
 <td>
  7. <a href="11-plot-multiple-shape-files.html">Plot multiple
@@ -407,7 +407,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 How can I create map compositions with custom legends using ggplot?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>03h 26m
+<span class="visually-hidden">Duration: </span>03h 21m
 </td>
 <td>
  8. <a href="12-handling-spatial-projection-and-crs.html">Handling
@@ -417,7 +417,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 What do I do when vector data don’t line up?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>04h 26m
+<span class="visually-hidden">Duration: </span>03h 51m
 </td>
 <td>
  9. <a href="13-intro-to-raster-data.html">Intro to Raster Data</a>
@@ -427,7 +427,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 R?<br>:::
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>04h 58m
+<span class="visually-hidden">Duration: </span>04h 23m
 </td>
 <td>
 10. <a href="14-plot-raster-data.html">Plot Raster Data</a>
@@ -437,7 +437,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 can I customize the colour scheme of a raster image?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>05h 33m
+<span class="visually-hidden">Duration: </span>04h 58m
 </td>
 <td>
 11. <a href="15-reproject-raster-data.html">Reproject Raster Data</a>
@@ -446,7 +446,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 How do I work with raster data sets that are in different projections?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>06h 05m
+<span class="visually-hidden">Duration: </span>05h 30m
 </td>
 <td>
 12. <a href="16-raster-calculations.html">Raster Calculations</a>
@@ -456,7 +456,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 defined locations?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>06h 35m
+<span class="visually-hidden">Duration: </span>06h 00m
 </td>
 <td>
 13. <a href="17-work-with-multi-band-rasters.html">Work with Multi-Band
@@ -466,7 +466,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 How can I visualize individual and multiple bands in a raster object?
 </td>
 </tr><tr><td>
-<span class="visually-hidden">Duration: </span>07h 00m
+<span class="visually-hidden">Duration: </span>06h 25m
 </td>
 <td>
 Finish
@@ -560,7 +560,7 @@ <h3 class="callout-title">GDAL, GEOS, and PROJ.4<a class="anchor" aria-label="an
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1">Windows</h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
 <div class="accordion-body">
 <p>To install the geospatial libraries, install the latest version <a href="https://cran.r-project.org/bin/windows/Rtools/" class="external-link">RTools</a></p>
 </div>
@@ -572,7 +572,7 @@ <h4 class="accordion-header" id="headingSolution1">Windows</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2">MacOS</h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
 <div class="accordion-body">
 <p>Install the geospatial libraries individually using <a href="https://brew.sh" class="external-link">homebrew</a>. Open Terminal.app and run the
 following commands:</p>
@@ -593,7 +593,7 @@ <h3 class="code-label">BASH<i aria-hidden="true" data-feather="chevron-left"></i
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution3" aria-expanded="false" aria-controls="collapseSolution3">
   <h4 class="accordion-header" id="headingSolution3">Linux</h4>
 </button>
-<div id="collapseSolution3" class="accordion-collapse collapse" aria-labelledby="headingSolution3" data-bs-parent="#accordionSolution3">
+<div id="collapseSolution3" class="accordion-collapse collapse" data-bs-parent="#accordionSolution3" aria-labelledby="headingSolution3">
 <div class="accordion-body">
 <p>Steps for installing the geospatial libraries will vary based on
 which form of Linux you are using. These instructions are adapted from
@@ -649,7 +649,7 @@ <h3 class="callout-title">UDUNITS<a class="anchor" aria-label="anchor" href="#ud
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution4" aria-expanded="false" aria-controls="collapseSolution4">
   <h4 class="accordion-header" id="headingSolution4">Linux</h4>
 </button>
-<div id="collapseSolution4" class="accordion-collapse collapse" aria-labelledby="headingSolution4" data-bs-parent="#accordionSolution4">
+<div id="collapseSolution4" class="accordion-collapse collapse" data-bs-parent="#accordionSolution4" aria-labelledby="headingSolution4">
 <div class="accordion-body">
 <p>Steps for installing the geospatial will vary based on which form of
 Linux you are using. These instructions are adapted from the <a href="https://github.com/r-spatial/sf" class="external-link"><code>sf</code> package’s
@@ -700,7 +700,7 @@ <h3 class="callout-title">R<a class="anchor" aria-label="anchor" href="#r"></a>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution5" aria-expanded="false" aria-controls="collapseSolution5">
   <h4 class="accordion-header" id="headingSolution5">Windows</h4>
 </button>
-<div id="collapseSolution5" class="accordion-collapse collapse" aria-labelledby="headingSolution5" data-bs-parent="#accordionSolution5">
+<div id="collapseSolution5" class="accordion-collapse collapse" data-bs-parent="#accordionSolution5" aria-labelledby="headingSolution5">
 <div class="accordion-body">
 <p>To install <code>R</code>, Windows users should select “Download R
 for Windows” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
@@ -717,7 +717,7 @@ <h4 class="accordion-header" id="headingSolution5">Windows</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution6" aria-expanded="false" aria-controls="collapseSolution6">
   <h4 class="accordion-header" id="headingSolution6">MacOS</h4>
 </button>
-<div id="collapseSolution6" class="accordion-collapse collapse" aria-labelledby="headingSolution6" data-bs-parent="#accordionSolution6">
+<div id="collapseSolution6" class="accordion-collapse collapse" data-bs-parent="#accordionSolution6" aria-labelledby="headingSolution6">
 <div class="accordion-body">
 <p>To install <code>R</code>, macOS users should select “Download R for
 macOS” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
@@ -735,7 +735,7 @@ <h4 class="accordion-header" id="headingSolution6">MacOS</h4>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution7" aria-expanded="false" aria-controls="collapseSolution7">
   <h4 class="accordion-header" id="headingSolution7">Linux</h4>
 </button>
-<div id="collapseSolution7" class="accordion-collapse collapse" aria-labelledby="headingSolution7" data-bs-parent="#accordionSolution7">
+<div id="collapseSolution7" class="accordion-collapse collapse" data-bs-parent="#accordionSolution7" aria-labelledby="headingSolution7">
 <div class="accordion-body">
 <p>To install <code>R</code>, Linux users should select “Download R for
 Linux” from RStudio and CRAN’s <a href="https://cloud.r-project.org" class="external-link">cloud download page</a>, which will
diff --git a/instructor/instructor-notes.html b/instructor/instructor-notes.html
index 5dba1bae..3a6ed751 100644
--- a/instructor/instructor-notes.html
+++ b/instructor/instructor-notes.html
@@ -424,11 +424,11 @@ <h3 id="09-open-and-plot-vector-layers-headingInstructor1">
 <a href="09-open-and-plot-vector-layers.html#headingInstructor1">Instructor Note</a><a class="anchor" aria-label="anchor" href="#09-open-and-plot-vector-layers-headingInstructor1"></a>
 </h3>
 <p>Make sure that the <code>sf</code> package and its dependencies are
-installed before the workshop. The installation can take quite some
-time, so allocate enough extra time before the workshop for solving
-installation problems. We recommend one or two installation ‘walk-in’
-hours on a day before the workshop and 15-30 minutes at the beginning of
-the first workshop day should be enough to tackle installation
+installed before the workshop. The installation can be lengthy, so
+allocate enough extra time before the workshop for solving installation
+problems. We recommend one or two installation ‘walk-in’ hours on a day
+before the workshop. Also, 15-30 minutes at the beginning of the first
+workshop day should be enough to tackle last-minute installation
 issues.</p>
 <hr>
 <br></section><section id="10-explore-and-plot-by-vector-layer-attributes"><h2 class="section-heading"><a href="10-explore-and-plot-by-vector-layer-attributes.html">Explore and plot by vector layer attributesQuery Vector Feature Metadata<a class="anchor" aria-label="anchor" href="#query-vector-feature-metadata"></a></a></h2>
diff --git a/instructor/key-points.html b/instructor/key-points.html
index f4c0a502..a5647998 100644
--- a/instructor/key-points.html
+++ b/instructor/key-points.html
@@ -439,7 +439,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul></section><section id="10-explore-and-plot-by-vector-layer-attributes"><h2 class="section-heading"><a href="10-explore-and-plot-by-vector-layer-attributes.html">Explore and plot by vector layer attributesQuery Vector Feature Metadata<a class="anchor" aria-label="anchor" href="#query-vector-feature-metadata"></a></a></h2>
@@ -455,10 +455,8 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 <li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul></section><section id="12-handling-spatial-projection-and-crs"><h2 class="section-heading"><a href="12-handling-spatial-projection-and-crs.html">Handling Spatial Projections &amp; CRS</a></h2>
 <hr class="half-width">
 <ul>
diff --git a/key-points.html b/key-points.html
index d4c73e0e..caabf632 100644
--- a/key-points.html
+++ b/key-points.html
@@ -437,7 +437,7 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 extent.</li>
 <li>Load spatial objects into R with the <code>st_read()</code>
 function.</li>
-<li>Spatial objects can be plotted directly with <code>ggplot</code>
+<li>Spatial objects can be plotted directly with <code>ggplot2</code>
 using the <code>geom_sf()</code> function. No need to convert to a data
 frame.</li>
 </ul></section><section id="10-explore-and-plot-by-vector-layer-attributes"><h2 class="section-heading"><a href="10-explore-and-plot-by-vector-layer-attributes.html">Explore and plot by vector layer attributesQuery Vector Feature Metadata<a class="anchor" aria-label="anchor" href="#query-vector-feature-metadata"></a></a></h2>
@@ -453,10 +453,8 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 <li>Use the <code>+</code> operator to add multiple layers to a
 ggplot.</li>
 <li>A plot can be a combination of multiple vector layers.</li>
-<li>Use the <code>show.legend</code> argument to set legend symbol
-types.</li>
-<li>Use the <code>scale_fill_manual()</code> function to set legend
-colors.</li>
+<li>Use the <code>scale_color_manual()</code> and
+<code>scale_fill_manual()</code> functions to set legend colors.</li>
 </ul></section><section id="12-handling-spatial-projection-and-crs"><h2 class="section-heading"><a href="12-handling-spatial-projection-and-crs.html">Handling Spatial Projections &amp; CRS</a></h2>
 <hr class="half-width">
 <ul>
diff --git a/md5sum.txt b/md5sum.txt
index 4a40c5f3..ce07513f 100644
--- a/md5sum.txt
+++ b/md5sum.txt
@@ -8,10 +8,10 @@
 "episodes/02-data-structures.Rmd" "f931ec7c4389445e191c4242601a9e08" "site/built/02-data-structures.md" "2024-01-29"
 "episodes/03-explore-data.Rmd" "e336f5c9503ce0e3339313803c3972d6" "site/built/03-explore-data.md" "2024-01-29"
 "episodes/04-intro-to-visualisation.Rmd" "23119233131530bb32bc9b02c9365b90" "site/built/04-intro-to-visualisation.md" "2024-01-29"
-"episodes/09-open-and-plot-vector-layers.Rmd" "900c7db9496a39a783274f609025892d" "site/built/09-open-and-plot-vector-layers.md" "2024-01-29"
-"episodes/10-explore-and-plot-by-vector-layer-attributes.Rmd" "5922efcd00e3b2211c879db06b3cccf6" "site/built/10-explore-and-plot-by-vector-layer-attributes.md" "2024-01-29"
-"episodes/11-plot-multiple-shape-files.Rmd" "410e905a4512c289ca0e04786b6fb262" "site/built/11-plot-multiple-shape-files.md" "2024-01-29"
-"episodes/12-handling-spatial-projection-and-crs.Rmd" "ed450613ffcd215227e938afd0c5b936" "site/built/12-handling-spatial-projection-and-crs.md" "2024-01-29"
+"episodes/09-open-and-plot-vector-layers.Rmd" "5385fff5dcb5d66ecd33d90845952dbd" "site/built/09-open-and-plot-vector-layers.md" "2024-01-29"
+"episodes/10-explore-and-plot-by-vector-layer-attributes.Rmd" "cd771d38f1d966e9bf07b2ea392b0ac1" "site/built/10-explore-and-plot-by-vector-layer-attributes.md" "2024-01-29"
+"episodes/11-plot-multiple-shape-files.Rmd" "1bddac335a8e6436c1109badb9c30915" "site/built/11-plot-multiple-shape-files.md" "2024-01-29"
+"episodes/12-handling-spatial-projection-and-crs.Rmd" "687a642d4424eff3926433517dc769d7" "site/built/12-handling-spatial-projection-and-crs.md" "2024-01-29"
 "episodes/13-intro-to-raster-data.Rmd" "ac403745679c50cc3d0ebade6b43732a" "site/built/13-intro-to-raster-data.md" "2024-01-29"
 "episodes/14-plot-raster-data.Rmd" "e74c1aae5e32478ba386f15a9b7b80d9" "site/built/14-plot-raster-data.md" "2024-01-29"
 "episodes/15-reproject-raster-data.Rmd" "9392077cf50153cc1443b270b904e28b" "site/built/15-reproject-raster-data.md" "2024-01-29"
diff --git a/pkgdown.yml b/pkgdown.yml
index afb39f91..941b43df 100644
--- a/pkgdown.yml
+++ b/pkgdown.yml
@@ -2,5 +2,5 @@ pandoc: 2.19.2
 pkgdown: 2.0.7
 pkgdown_sha: ~
 articles: {}
-last_built: 2024-01-29T15:54Z
+last_built: 2024-01-29T15:59Z
 
diff --git a/sitemap.xml b/sitemap.xml
index f049e464..e933dd1d 100644
--- a/sitemap.xml
+++ b/sitemap.xml
@@ -39,6 +39,9 @@
   <url>
     <loc>https://carpentries-incubator.github.io/r-geospatial-urban/17-work-with-multi-band-rasters.html</loc>
   </url>
+  <url>
+    <loc>https://carpentries-incubator.github.io/r-geospatial-urban/2-vector-slides.html</loc>
+  </url>
   <url>
     <loc>https://carpentries-incubator.github.io/r-geospatial-urban/3-raster-slides.html</loc>
   </url>