[GRASS-SVN] r51450 - grass/branches/develbranch_6/vector/v.net.allpairs

[svn_grass at osgeo.org]

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>