[GRASS-dev] r.watershed2 with MFD

Dylan Beaudette debeaudette at ucdavis.edu
Fri Dec 5 17:18:22 EST 2008


On Friday 05 December 2008, Markus Metz wrote:
> Dylan Beaudette wrote:
> > On Fri, Dec 5, 2008 at 1:55 AM, Markus Metz <markus_metz at gmx.de> wrote:
> >> I took the request for MFD support in r.watershed by Helena and Dylan to
> >> heart and implemented it, but still need a few more days to clean up the
> >> code, then I want to submit it as r.watershed2.mfd to grass-addons.
> >
> > Is there any way to
> > cleanly merge this with the existing r.watershed code in SVN so that
> > we can test it?
>
> Also considering Michael's remarks, I suggets that I then not submit to
> grass-addons, but to grass 7. Not to grass-6.4.x, because this code is
> now more experimental and documentation still needs to be written.

Good points. Perhaps my anxiousness to give the new MFD functionality clouded 
my better judgment :) .


> The MFD algorithm seems to be robust and produces the expected results
> with nice differences according to the convergence factor, but the other
> outputs are different and I don't know yet if this is ok and desired or
> not. The basins and half-basins are different, less so for coarser
> resolution, rather disastrous with MFD for the 1m LIDAR DEM in the North
> Carolina dataset. It seems that such a DEM should be processed with
> coarser resolution to obtain basins and half-basins that make sense,
> apparently both for SFD and MFD, but these a just first impressions.
> Slope length (LS for USLE) and slope steepness (S for USLE) are about
> 99.9% identical between SFD and MFD with the DEM <elevation> in the
> North Carolina dataset. Streams are again different, i.e. MFD streams
> need to be thinned then they are very similar to SFD, but MFD streams
> make sense.
> Once I have added MFD to segmented mode too and updated the
> documentation, the module is ready to be submitted and scrutinised by
> others.

Looking forward to it!

> This is no easy feat to modify r.watershed, I want to make sure the old
> behaviour is preserved when adding new functionality and I need some
> more time before submitting. I don't like to submit code with bugs...
>
> Markus Metz

Indeed. Please go through the development cycle as suggested by experienced 
developers.

Cheers,

Dylan



-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341


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