README.md

GeoTrellis landsat tutorial project

This tutorial goes over how to process a single landsat image on a single machine, using GeoTrellis and spark. We will create a server that will serve out tiles onto a web map that represent an NDVI calculation on our image. The calculation of the NDVI and the rendering of the PNG tile will be dynamic and happen per tile request.

Download a Landsat image

Download this landsat image: https://s3.amazonaws.com/geotrellis-sample-datasets/landsat/LC80140322014139LGN00.tar.bz

Un-tar this into data/landsat

Creating a 2 band geotiff from the red and NIR bands masked with the QA band

The code in src/main/scala/tutorial/MaskRedAndNearInfrared.scala will do this.

> ./sbt run

Select the tutorial.MaskRedAndNearInfrared to run.

This will produce data/r-nir.tif

Create a PNG of an NDVI of of our image.

The code in src/main/scala/tutorial/CreateNDVIPng.scala will do this.

> ./sbt run

Select the tutorial.CreateNDVIPng to run.

This will produce data/ndvi.png

Preprocessing our data with GDAL

We want to use the GDAL library to do some preproccessing of our data

Reproject our image using gdalwarp

First, we want to reproject our data into "web mercator" (EPSG:3857)

In the data directory:

> gdalwarp -t_srs EPSG:3857 r-nir.tif r-nir-wm.tif

Tile out the R and NIR bands with gdal_retile.py

We'll want to work with smaller tiles of our image when working with spark. Tile them out using gdal_retile.py

In the data directory:

> mkdir landsat-tiles
> gdal_retile.py -ps 512 512 -targetDir landsat-tiles/ r-nir-wm.tif

Transform the tiled image into z/x/y indexed GeoTiffs.

This step will transform the tiles we made last step into a set of GeoTiffs representing a version of the raster in GeoTiffs according to the Slippy Map tile coordinate representation, at multiple zoom levels.

The code is in the src/main/scala/tutorial/TileGeoTiff.scala file.

> ./sbt run

Select the tutorial.TileGeoTiff to run.

Tiles will be generated in the data/tiles directory.

Serve out dynamically created NDVI images using Spray

This step will start a server that will serve out NDVI images onto a web map.

The code is located in the src/main/scala/tutorial/ServeNDVI.scala file.

> ./sbt run

Select the tutorial.ServeNDVI to run.

You can either go tonow open static/index.html and see our NDVI tiles on a web map.