Hamish, That sounds about right. Which is why I'm trying to modify r.walk/r.drain to be able to return the actual least-cost path. I've finished the r.walk bit but I'm having trouble modifying the r.drain function.
Re my original question, would it be better to make a separate module or modify r.drain? -Colin On Tue, Jun 24, 2008 at 2:06 PM, Hamish <[EMAIL PROTECTED]> wrote: > Dylan: >> > Interesting post Colin. Can you comment on the differences between >> > r.drain and r.walk in this example [1], in light of your findings? >> > 1. http://casoilresource.lawr.ucdavis.edu/drupal/node/544 > > teaching r.walk to follow ridgelines when possible would be cool for back > country stuff. Perhaps r.mapcalc multiply the slope-cost input map with a > r.param.scale feature map that likes ridges and saddles but doesn't like > gullies and pits? treelines too. > > Also set cost map to NULL if slope > x so it doesn't have you crossing > cumulatively short but physically challenging 20m cliffs. > > > Colin: >> Excellently documented example by the way. >> >> The path is probably quite similar but the point is that there is >> currently no way to ensure that the r.drain path conforms to the >> same path as the optimal path of cost accumulation (calculated >> by r.walk or r.cost). > > AFAIR r.drain just blindly climbs to the next up/downhill D8 cell, in a loop, > until it can climb/drop no more. thus it is not "least" cost at all, just one > valid solution? (??) > > > Hamish > > > > > > _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
