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- Date: Sun, 15 Jul 2001 18:26:51 -0600
- From: "Roger S. Miller" <rgrmill@rt66.com>
- X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.0.27 i586)
- X-Accept-Language: en
- To: Markus Neteler <neteler@geog.uni-hannover.de>
- Subject: r.drain -- new version
- 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
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