On Fri, Jan 9, 2015 at 5:12 AM, Takenori KANAI <[email protected]> wrote: > Markus N and Markus M, > > Thankyou for your response. > > I see. If on the first step, more surrounding cells have the same > minimum cost, which is the first cell encountered > used (like follows: a is greater than surraounding cells)? > I'm sorry the question on the abc. > > 2 2 2 > 2 a 2 > 2 2 2 > I was wrong. In this case all cells with the minimum cost are added and the direction is resolved later. The way how this direction is resolved is not documented, unfortunately. There are 247 possible cases where directions need to be resolved, these have been hard-coded.
Markus M > Thanks > > Takenori K. > > To my knowledge there is no scientific paper available related to the > r.drain algorithm. > It has been written by Roger S. Miller in 2001 (replacing an older and > less functional version). > > You may see the internals here in the code base: > http://trac.osgeo.org/grass/browser/grass/trunk/raster/r.drain > > Maybe other users know more about this algorithm family? > > Best > Markus N > > r.drain simply follows the lowest cost in the surrounding cells (must > be lower than the current cell). If more surrounding cells have the > same minimum cost, the first cell encountered is used. > > Markus M > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
