[GRASS-SVN] r46550 - grass/trunk/vector/v.net

[svn_grass at osgeo.org]

Author: mmetz
Date: 2011-06-03 09:16:31 -0700 (Fri, 03 Jun 2011)
New Revision: 46550

Modified:
   grass/trunk/vector/v.net/v.net.html
Log:
update manual

Modified: grass/trunk/vector/v.net/v.net.html
===================================================================
--- grass/trunk/vector/v.net/v.net.html	2011-06-03 16:16:06 UTC (rev 46549)
+++ grass/trunk/vector/v.net/v.net.html	2011-06-03 16:16:31 UTC (rev 46550)
@@ -1,10 +1,28 @@
 <h2>DESCRIPTION</h2>
 
-<em>v.net</em> is used for vector network maps maintenance.  It
-reports the current network graph status. It also permits to globally
-insert missing nodes or arcs and to connect unconnected nodes to the
-graph within a given distance threshold.
+<em>v.net</em> is used for network preparation and maintenance. 
+It permits to insert missing nodes or arcs and to connect unconnected 
+nodes to the network within a given distance threshold. 
+It can also report the current network graph status. 
 
+<p>
+In terms of network analysis, a network consists of nodes connected by 
+arcs. In a vector map prepared for network analysis, nodes are represented 
+by the grass-internal geometry type <em>node</em> and arcs by the geometry 
+type <em>line</em>. If a <em>line</em> consists of several vertices and 
+segments (the typical case), only its staring and ending vertex are 
+regarded as network nodes. Further more, explicit starting and ending 
+nodes for e.g. a least costly path search or subnetwork allocation are 
+represented by the geometry type point.
+
+<p>
+In general, network analysis will find the least costly (shortest or 
+fastest) path from point A to point B by follwing the existing lines. 
+This implies that these points must lie at the start or end point of a 
+line with is part of the network. If no line is starting or ending at a 
+given point, this point is not part of the network, i.e. the point is 
+unconnected and unreachable.
+
 <h3>NOTES</h3>
 
 If vector editing is required to modify the