[GRASS-SVN] r51450 -
grass/branches/develbranch_6/vector/v.net.allpairs
svn_grass at osgeo.org
svn_grass at osgeo.org
Sun Apr 15 02:54:51 EDT 2012
Author: mmetz
Date: 2012-04-14 23:54:51 -0700 (Sat, 14 Apr 2012)
New Revision: 51450
Modified:
grass/branches/develbranch_6/vector/v.net.allpairs/description.html
Log:
update documentation
Modified: grass/branches/develbranch_6/vector/v.net.allpairs/description.html
===================================================================
--- grass/branches/develbranch_6/vector/v.net.allpairs/description.html 2012-04-15 06:54:33 UTC (rev 51449)
+++ grass/branches/develbranch_6/vector/v.net.allpairs/description.html 2012-04-15 06:54:51 UTC (rev 51450)
@@ -1,37 +1,61 @@
<h2>DESCRIPTION</h2>
-<em>v.net.allpairs</em> computes the shortest path between each select
-node and all other nodes.
+<em>v.net.allpairs</em> computes the shortest path between each selected
+node and all other selected nodes.
+<p>
+If the input vector has been prepared with <em>v.net</em> and
+<em>v.net.allpairs</em> should use cost columns, further preparation is
+of the input vector required. In contrast to the output of <em>v.net</em>
+and the behaviour of other <em>v.net.*</em> modules, <em>v.net.allpairs</em>
+uses the same layer to read cost columns for arcs and to read node
+categories. Therefore new, unique categories for points must be added
+to the layer with cost columns for lines with <em>v.category</em>.
+<br>
+If <b>abcolumn</b> is not given then then the same costs are used for
+forward and backward arcs.
<h2>NOTES</h2>
-An attribute table is created and linked to <b>layer</b>. The table
+An attribute table is created and linked to layer 1. The table
contains three columns: <em>cat</em>, <em>to_cat</em>, <em>cost</em>.
Each entry denotes the cost of the shortest path from <em>cat</em> to
<em>to_cat</em>. If the cost is negative then no path exists. If points
-are specified by <b>cats, layer</b> or <b>where</b> parameters then the
-table is filled only for the selected points. In other words, <em>cat</em>
-columns contains only selected points but the distances are computed and
-updated for <em>all</em> other nodes.<br>
-If flag <b>-a</b> is set then new points are added on nodes without points.
-These points have the largest category. Precisely, the category of each new
-point is larger than any of the old categories. If the flag is not set
-then no new points are created and hence the attribute table stores the
-costs only between the points already present in the input. Output consists
-of all points mentioned in either of the columns.<br>
-If <b>abcolumn</b> is not given then then the same costs are used for
-forward and backward arcs.
+are specified by <b>cats, layer</b> or <b>where</b> parameters then
+the table is filled only for the selected points.
+<br>
+If the <b>-a</b> flag is set then new points are added on nodes without
+nodes. These points have the largest category. Precisely, the category
+value of each new point is larger than any of the old categories. Note
+that these new points are not included in the output table.
-<h2>EXAMPLES</h2>
+<h2>EXAMPLE</h2>
-Find shortest path from each intersection with pedestrian crossing to
-every other point using <em>SHAPE_LEN</em> for the cost of traversing
-the arcs in both directions.
+Find shortest path along roads from selected archsites (Spearfish sample
+dataset):
<div class="code"><pre>
-v.net.allpairs input=roads output=roads_pairs afcol=SHAPE_LEN where="crossing=1"
+# prepare network: connect archsites to roads with threshold 200
+v.net input=roads at PERMANENT points=archsites at PERMANENT \
+output=roads_net operation=connect thresh=200
+
+# verify result
+v.category input=roads_net option=report
+
+# only lines should have a category in layer 1
+# only points should have a category in layer 2
+
+# shortest path between all points with categories 1 - 5 in layer 2
+v.net.allpairs input=roads_net layer=2 cats=1-5 out=roads_net_all
+v.db.select roads_net_all
</pre></div>
-<p>
+Result in matrix form:
+<div class="code"><pre>
+from\to 1 3 4 5
+1 0 18820.386 17206.651 17373.274
+3 18820.386 0 1739.079 9040.575
+4 17206.651 1739.079 0 7426.84
+5 17373.274 9040.575 7426.84 0
+</pre></div>
<h2>SEE ALSO</h2>
@@ -44,7 +68,8 @@
<h2>AUTHORS</h2>
Daniel Bundala, Google Summer of Code 2009, Student<br>
-Wolf Bergenheim, Mentor
+Wolf Bergenheim, Mentor<br>
+Markus Metz
<p>
<i>Last changed: $Date$</i>
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