On Friday 29 February 2008, Jonathan Greenberg wrote: > If I have a r.cost surface calculated from a set of vector points used > as starting points, and some cost surface, is there any way to easily > retrieve the SOURCE vector ID that leads to the lowest cost to get to > any cell in the raster? E.g. from a given point, where is the point > that costs the least to get to? > > --j
r.cost is generally used in conjunction with r.drain. First a cost surface from: - a starting point - a set of starting points - a line segment is generated to: - the edges of the region - a stopping point - a set of stopping points Then r.drain is used to compute the least-cost-path between the starting point/points/line and some arbitrary end point. With the idea that you will "drain" some water down-slope the cost surface, back to your starting point/points/line. To find the least-cost-path between *any two points* I have generally found it simplest to run r.cost + r.drain for every start/stop combination that I am interested in. An example is posted here: http://casoilresource.lawr.ucdavis.edu/drupal/node/244 note that the code describing this process on the referenced page is actually an un-rolled foreach loop. Hope that helps a little, Dylan -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
