v.lfp.html

<h2>DESCRIPTION</h2>
<em>v.lfp</em> converts a longest flow path raster map created by
<em>r.lfp</em> to a vector map.

<h2>NOTES</h2>

<em>v.lfp</em> creates a longest flow path vector map by processing an output
raster map from <em>r.lfp</em>. Since a longest flow path raster map can have
cell clusters, simply converting the raster map to a vector map using
<em>r.to.vect</em> can result in closed rectangular shapes in the output vector
map, which represent multiple but equivalent longest flow paths. This module
first converts the input raster map to a vector map, removes dangles, and merge
the remaining lines. The module repeats this process until there remains only
one line feature, which is the final longest flow path.

<h2>EXAMPLE</h2>

<div class="code"><pre>
# Creates a longest flow path raster map.
r.watershed elevation=elev drainage=drain
r.water.outlet input=drain output=basin coordinates=-888857.11,1117788.38
r.lfp input=drain output=lfp coordinates=-888857.11,1117788.38

# The end point of lfp can be the headwater of the longest flow path.
v.lfp input=lfp output=lfp

# Make sure the end point of lfp2 is the outlet point.
v.lfp input=lfp output=lfp2 coordinates=-888857.11,1117788.38
</pre></div>

<h2>SEE ALSO</h2>

<em>
<a href="r.lfp.html">r.lfp</a>
</em>
<br>
<a href="http://idea.isnew.info/how-to-calculate-the-longest-flow-path-in-grass-gis.html">How to calculate the longest flow path in GRASS GIS</a>

<h2>AUTHOR</h2>

<a href="mailto:grass4u@gmail com">Huidae Cho</a>

<p><i>Last changed: $Date: 2016-08-15 17:01:53 -0400 (Mon, 15 Aug 2016) $</i>