[GRASS-dev] r.watershed2 with MFD

[Helena Mitasova]

Markus,

at this point, as you suggest, the best would be to work on this in  
grass7 - do you have SVN commit access?

Helena


On Dec 5, 2008, at 3:02 PM, 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.
> 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.

You may be using a threshold that is too small.
>
> 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.
>
> 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
>
>
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