[GRASS-SVN] r37931 - grass/trunk/vector/v.clean
svn_grass at osgeo.org
svn_grass at osgeo.org
Thu Jun 18 14:49:04 EDT 2009
Author: mmetz
Date: 2009-06-18 14:49:04 -0400 (Thu, 18 Jun 2009)
New Revision: 37931
Modified:
grass/trunk/vector/v.clean/v.clean.html
Log:
another manual update
Modified: grass/trunk/vector/v.clean/v.clean.html
===================================================================
--- grass/trunk/vector/v.clean/v.clean.html 2009-06-18 18:35:55 UTC (rev 37930)
+++ grass/trunk/vector/v.clean/v.clean.html 2009-06-18 18:49:04 UTC (rev 37931)
@@ -4,7 +4,8 @@
maps.
<h3>Break lines/boundaries</h3>
-
+<em>tool=break</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -16,7 +17,8 @@
<em>v.clean tool=break,rmdupl</em>.
<h3>Remove duplicate geometry features</h3>
-
+<em>tool=rmdupl</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -29,34 +31,37 @@
The <em>rmdupl</em> tool should be used after breaking lines and
breaking polygons.
-<h3>Remove dangles</h3>
-
+<h3>Remove dangles or change boundary dangles to type line</h3>
+<em>tool=rmdangle</em> and <em>tool=chdangle</em>
+<p>
Threshold gives maximum line/boundary length in map units, degrees for
-latlon. Dangles shorter than <em>thresh</em> will be removed.
+latlon. Dangles shorter than <em>thresh</em> are removed sequentially.
All dangles will be removed if <em>thresh</em> < 0.
<p>
-The <em>rmdangle</em> tool removes dangling lines/boundaries shorter than
-<em>thresh</em>. A line/boundary is considered to be a dangle if no other
-line of given <em>type</em> is on at least one end node. If a dangle is
-formed by several lines, such a string of lines is taken as one dangle
-and everything is deleted if the combined length is shorter than
-<em>thres</em> or <em>thres</em> is < 0. If the combined length is
-larger than <em>thresh</em>, nothing is deleted. The <em>rmdangle</em>
-tool is useful to remove incorrect boundaries after other cleaning
-operations. Areas can then be successfully built.
-
-<h3>Change boundary dangles to type line</h3>
-
-Threshold gives maximum line/boundary length in map units, degrees for
-latlon. All boundary dangles shorter than <em>thresh</em> will be changed
-to type line. Threshold is ignored if < 0.
+A line/boundary is considered to be a dangle if no other line of given
+<em>type</em> is on at least one end node. If a dangle is formed by
+several lines, such a string of lines is taken as one dangle and line
+lengths are summarized. The <em>rmdangle</em> tool deletes a dangle if
+the (combined) length is shorter than <em>thres</em> or <em>thres</em>
+< 0. If the combined length is larger than <em>thresh</em>, nothing
+is deleted.
<p>
+With <em>thresh</em> < 0, only closed loops and lines connecting
+loops will remain. This is useful to remove all incorrect boundaries
+after other cleaning operations with <em>thres</em> is < 0. Areas can
+then be successfully built.
+<p>
+To preferentially remove shortest dangles first, a first pass with a
+small <em>thresh</em> value can be followed by subsequent passes with
+increasing <em>thresh</em> values.
+<p>
The <em>chdangle</em> tool is similar to the <em>rmdangle</em> tool, but
works only on boundaries and changes dangling boundaries to lines
instead of removing dangles.
-<h3>Remove or change bridges connecting an area and an island or two
-islands</h3>
+<h3>Remove or change bridges connecting an area and an island or two islands</h3>
+<em>tool=rmbridge</em> and <em>tool=chbridge</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -79,21 +84,26 @@
</pre></div>
<p>
Islands and areas must be already clean, i.e. without dangles or small
-angles.
+angles, e.g. <em>v.clean type=boundary tool=rmdangle,rmsa,break,rmdupl,rmbridge
+thresh=-1,0,0,0,0</em>.
<h3>Snap lines to vertex in threshold</h3>
-
+<em>tool=snap</em>
+<p>
Threshold gives maximum distance to another vertex in map units,
-degrees for latlon. If there is no other vertex within <em>thresh</em>,
-no snapping will be done.
-
+degrees for latlon.
+<p>
The <em>snap</em> tool snaps vertices to another vertex not farther away
-than <em>thresh</em>. The <em>type</em> option can have a strong
-influence on the result. Snapped boundaries may need to be cleaned with
-<em>rmdangle,break,rmdupl</em>.
+than <em>thresh</em>. If there is no other vertex within <em>thresh</em>,
+no snapping will be done. The <em>type</em> option can have a strong
+influence on the result. A too large threshold and <em>type=boundary</em>
+can severely damage area topology.
+<p>
+Snapped boundaries may need to be cleaned with <em>rmdangle,break,rmdupl</em>.
<h3>Remove duplicate area centroids</h3>
-
+<em>tool=rmdupl</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -102,7 +112,8 @@
<h3>Break (topologically clean) areas (imported from a non topological
format like ShapeFile)</h3>
-
+<em>tool=bpol</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -121,7 +132,8 @@
<em><a href=v.generalize.html>v.generalize</a></em> instead.
<h3>Remove small areas</h3>
-
+<em>tool=rmarea</em>
+<p>
Threshold gives area size in map units, square meters for latlon.
<p>
The <em>rmarea</em> tool removes all areas <= <em>thresh</em>. The
@@ -130,7 +142,8 @@
area is merged with a larger area.
<h3>Remove all lines or boundaries of zero length</h3>
-
+<em>tool=rmline</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -139,7 +152,8 @@
boundaries are redundant and do not influence area topology.
<h3>Remove small angles between lines at nodes</h3>
-
+<em>tool=rmsa</em>
+<p>
Threshold does not apply, use dummy value if <em>v.clean</em> is
run with several tools.
<p>
@@ -232,7 +246,12 @@
</pre></div>
v.clean type=boundary would remove nothing.
+<h3>Repeatedly remove dangling lines up to 50m length</h3>
+<div class="code"><pre>
+v.clean input=testmap output=cleanmap type=line tool=rmdangle,rmdangle,rmdangle,rmdangle thresh=5,10,20,50
+</pre></div>
+
<h2>AUTHORS</h2>
David Gerdes, U.S. Army Construction Engineering Research Laboratory<br>
More information about the grass-commit
mailing list