[GRASS5] Re: r.drain -- new version

Markus Neteler neteler at geog.uni-hannover.de
Wed Jul 18 19:07:32 EDT 2001


(cc to grass5)

many thanks for your cmoplete rewrite of r.drain - now it seems to
run correctly! I have tested with FCELL and DCELL map.

The new code is in CVS now.

Many thanks again for your work,


On Sun, Jul 15, 2001 at 06:26:51PM -0600, Roger S. Miller wrote:
> Markus,
> I worked on the original r.drain for a while and wasn't really able to
> understand what it was doing, much less where the problem was.  I
> figured that I might be able to spend the rest of the weekend figuring
> it out and in the end I would still have a program with unusual behavior
> in flat spots.  I decided instead to finish the version that I started
> based on r.fill.dir.
> My version of r.drain (which I called r.d2) is in the attached zip file.
> r.d2 reproduces most of the behavior of r.drain.  It does not use the
> "null_value" option and it won't read input from a sites file.  It uses
> all of the flags defined for r.drain.  My first draft of the model
> didn't correctly handle the ew,ns and diagonal resolutions (as
> r.fill.dir does not).  I believe that I fixed that problem.  There are
> also some other minor behaviors that differ a little from r.drain.
> r.d2 runs pretty quickly on a small, clean dem, but it can take quite a
> while  to run on a large cell map - particularly one with very many
> areas where the flow directions are ambiguous.  I didn't write anything
> into the program to warn the user about the execution time.
> I tested it on the fcell map that you sent me when this issue first came
> up and on a lat-long cell map.  It worked well in both cases.  The
> version of r.fill.dir that I started with was the version I had archived
> here, which was not updated for all the changes needed to make
> r.fill.dir run on all of our platforms.  I built in the changes that I
> could remember, but there may be a few more that come up when you try to
> compile it on the Cray.
> I hope this meets your needs.
> Roger

Markus Neteler *  University of Hannover
Institute of Physical Geography and Landscape Ecology
Schneiderberg 50 * D-30167 Hannover * Germany
Tel: ++49-(0)511-762-4494  Fax: -3984

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