[GRASSLIST:2127] Re: [GRASS5] Re: r.drain -- new version

Rich Shepard rshepard at appl-ecosys.com
Wed Jul 18 22:17:59 EDT 2001

On Wed, 18 Jul 2001, Roger S. Miller wrote:

> The various modules originated at different times and some from different
> authors.  I suspect that they have never been integrated into a single
> module mostly because noone has ever simultaneously had both the need and
> the time to integrate them.


  This is what I suspected, but I'm surprised that consolidation wasn't done
as part of the move to 5.x.

> I also don't think there's a lot of reasons to integrate them.  The main
> reason would be to make sure that all of the watershed analysis tools
> produce consistent results.  That lack of consistency can be a problem.

  Without a lot of looking, I don't know that they use the same algorithms.
That can lead to problems as you noted above.

> While I agree there is a lot of overlap between these tools I don't have
> much trouble distinguishing between them.

  I agree that with familiarity, everything becomes "intuitive". (Ahem!
Pardon me.) But, I could make an argument for using the most robust,
"correct" algorithm currently available to route flow, for example, rather
than having the result depend on which module is used. New users in
particular are subject to the most confusion and uncertainty. And, I don't
recall seeing anything in the man pages (on a consistent basis, at least)
that describes the algorithm implemented.

  The reason I make a big deal about this is so much of what I do is on
projects that are controversial, sensitive, and become politically charged.
I want to know that I can defend my reputation and my work when some project
opponent raises a challenge, or the project ends up in court, at the
Interior Board of Land Appeals, or similar settings.



Dr. Richard B. Shepard, President

                       Applied Ecosystem Services, Inc. (TM)
            2404 SW 22nd Street | Troutdale, OR 97060-1247 | U.S.A.
 + 1 503-667-4517 (voice) | + 1 503-667-8863 (fax) | rshepard at appl-ecosys.com
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