[GRASS-SVN] r58595 - grass/branches/releasebranch_6_4/raster/r.to.vect
svn_grass at osgeo.org
svn_grass at osgeo.org
Fri Jan 3 10:40:22 PST 2014
Author: neteler
Date: 2014-01-03 10:40:22 -0800 (Fri, 03 Jan 2014)
New Revision: 58595
Modified:
grass/branches/releasebranch_6_4/raster/r.to.vect/description.html
Log:
r.to.vect manual: examples added
Modified: grass/branches/releasebranch_6_4/raster/r.to.vect/description.html
===================================================================
--- grass/branches/releasebranch_6_4/raster/r.to.vect/description.html 2014-01-03 18:28:50 UTC (rev 58594)
+++ grass/branches/releasebranch_6_4/raster/r.to.vect/description.html 2014-01-03 18:40:22 UTC (rev 58595)
@@ -4,17 +4,16 @@
layer, extracts points, lines or area edge features from it, converts data
to GRASS vector format.
-<h3>Points</h3>
+<h3>Point conversion</h3>
-The <em>r.to.vect</em> program extracts data from a GRASS raster map layer and stores output
-in a new GRASS <em>vector</em> file.
+The <em>r.to.vect</em> program extracts data from a GRASS raster map
+layer and stores output in a new GRASS <em>vector</em> file.
-<h3>Lines</h3>
+<h3>Line conversion</h3>
<em>r.to.vect</em> assumes that the <em>input</em> map has been thinned
using <em><a href="r.thin.html">r.thin</a></em>.
<p>
-
<em>r.to.vect</em> extracts vectors (aka, "arcs") from a
raster map. These arcs may represent linear features
(like roads or streams), or may represent area edge
@@ -22,7 +21,6 @@
units).
<p>
-
<em><a href="r.thin.html">r.thin</a></em> and <em>r.to.vect</em>
may create excessive nodes at every junction, and may create small spurs
or "dangling lines" during the thinning and vectorization process.
@@ -30,7 +28,7 @@
<em><a href="v.clean.html">v.clean</a></em>.
-<h3>Areas</h3>
+<h3>Area conversion</h3>
<em>r.to.vect</em> first traces the perimeter of each unique
area in the raster map layer and creates vector data to
@@ -39,10 +37,9 @@
resultant vector area edge data.
<p>
-
A true vector tracing of the area edges might appear
blocky, since the vectors outline the edges of raster data
-that are stored in rectangular cells. To produce a
+that are stored in rectangular cells. To produce a
better-looking vector map, <em>r.to.vect</em> smoothes the
corners of the vector data as they are being extracted. At
each change in direction (i.e., each corner), the two
@@ -57,30 +54,84 @@
error introduced by smoothing.
<p>
+<em>r.to.vect</em> extracts only area edges from the named raster
+input file. If the raster map contains other data (i.e., line edges,
+or point data) the output may be wrong.
-<em>r.to.vect</em> extracts only area edges from the named raster input file.
-If the raster map contains other data (i.e., line edges, or point data) the
-output may be wrong.
+<h2>EXAMPLES</h2>
+The examples are based on the North Carolina sample dataset:
+<p>
+<b>Conversion of raster points to vector points:</b>
+<p>
+Random sampling of points:
+<div class="code"><pre>
+g.region rast=elevation -p
+# random sampling of points (note that r.random also writes vector points)
+r.random elevation raster_output=elevrand1000 n=1000
+r.to.vect input=elevrand1000 output=elevrand1000 feature=point
+# univariate statistics of sample points
+v.univar elevrand1000 column=value type=point
+# compare to univariate statistics on original full raster map
+r.univar elevation
+</pre></div>
+<p>
+
+<b>Conversion of raster lines to vector lines:</b>
+<p>
+Vectorization of streams in watershed basins map:
+<div class="code"><pre>
+g.region rast=elevation -p
+r.watershed elev=elevation stream=elev.streams thresh=50000
+r.to.vect -s input=elev.streams output=elev_streams feature=line
+# drop "label" column which is superfluous in this example
+v.db.dropcol map=elev_streams column=label
+v.db.renamecol map=elev_streams column=value,basin_id
+# report length per basin ID
+v.report map=elev_streams option=length units=meters
+</pre></div>
+<p>
+
+<b>Conversion of raster polygons to vector polygons:</b>
+<p>
+Vectorization of simplified landuse class map:
+<div class="code"><pre>
+g.region rast=landclass96 -p
+# we smooth corners of area features
+r.to.vect -s input=landclass96 output=my_landclass96 feature=area
+v.colors my_landclass96 color=random
+# show colorized vector map
+d.mon x0
+d.vect my_landclass96 -a
+</pre></div>
+
<h2>BUGS</h2>
For feature=line the input raster map MUST be thinned by
<em><a href="r.thin.html">r.thin</a></em>;
if not, <em>r.to.vect</em> may crash.
-<h2>AUTHOR</h2>
-<b>Points</b><br>
+<h2>SEE ALSO</h2>
+
+<em>
+<a href="g.region.html">g.region</a>,
+<a href="r.thin.html">r.thin</a>,
+<a href="v.clean.html">v.clean</a>
+</em>
+
+<h2>AUTHORS</h2>
+<b>Point support</b><br>
Bill Brown<br>
<br>
-<b>Lines</b><br>
+<b>Line support</b><br>
Mike Baba<br>
DBA Systems, Inc.<br>
10560 Arrowhead Drive<br>
Fairfax, Virginia 22030<br>
<br>
-<b>Areas</b><br>
+<b>Area support</b><br>
<em>Original</em> version of <em>r.poly</em>:
<br>
Jean Ezell and Andrew Heekin,
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