[GRASS-user] r.basin: Completes on Some Basins, Fails on Others

[Rich Shepard]

On Thu, 7 Jun 2012, Helmut Kudrnovsky wrote:

> sure, it's taken from http://www.surfaces.co.il/?p=241

   Micha wrote an excellent description that answered a number of questions
for me. Now I'm ready to try r.basin again and want to check the validity of
my understanding of how I got where I now am and where it's going with
r.basin.

   The input to r.stream.extract came from r.watershed with this command:

r.watershed elev=dem_10m acc=facc drain=fdir basin=catch stream=str thresh=50000

and was followed by r.stream.extract:

r.stream.extract elev=dem_10m acc=facc thresh=1000 stream_rast=rstream stream_vect=vstream

   To find the sub-basin outlets,

v.patch in=catchments,vstream out=basin_stream

and

v.clean in=basin_vstream out=basin_vstream_clean tool=break error=cross_points

   Prior to running v.out.ascii to save the cross_points in a text file I
carefully manually deleted extraneious tiny sub-basins and cross_points at
the confluences of stream channels. This reveals that many cross_points are
not on sub-basin boundaries generated by r.watershed.

   In Micha's blog article the cross_points.txt file is used as input to
r.water.outlet which generates the appropriate catchments. I assume this is
also true for r.basin; i.e., it will generate its own basins and sub-basins
based on the outlet points in the cross_points.txt file. Is this assumption
correct?

   My thanks to Markus(M), Madi, Helmut, and Micha.

Rich