[GRASS-user] SRTM r.watershed at multiple scales

[Stefan Lüdtke]

Hi,
I experienced  a similar point, but, if I remember right, this was
because I set the computational region to the extend of the catchment
produced by r.water.outlet. So maybe the MASK has a similar effect and
r.watershed needs kind of buffer. Should be easy to check ...

HTH,

Stefan



On 02/20/2014 07:11 PM, Michel Wortmann wrote:
> Here is what I think is strange though about your explanation, Markus:
> If I first mask a watershed produced with r.water.outlet and then use
> r.watershed to produce subbasins, it doesnt include the entire area of
> the watershed but leaves small areas out, although these areas belong to
> it. Is this a threshold problem?
> 
> Tom, see image attached.
> 
> Michel
> 
> On 02/19/2014 04:42 PM, Thomas Adams wrote:
>> I've been using GRASS 7 for this and have not seen a problem -- I hope
>> I'm not overlooking the issue. Michel, can you provide an image that
>> shows this?
>>
>> Thanks,
>> Tom
>>
>> On Wednesday, February 19, 2014, Michel Wortmann
>> <wortmann at pik-potsdam.de <mailto:wortmann at pik-potsdam.de>> wrote:
>>
>>     Markus,
>>     last year you asked me whether the r.watershed output is not
>>     aligned to the r.water.outlet output in GRASS7 (s.b.). Ie. it
>>     leaves small areas out. Back then, I wasnt using GRASS7, but I can
>>     confirm now that it still does it and it is still rather annoying.
>>     Have you ever heard of the reasons or attempted to fix this?
>>     Thanks,
>>     Michel
>>
>>     On 08/26/2013 03:25 PM, Markus Neteler wrote:
>>
>>         On 08/22/2013 08:52 AM, Markus Neteler wrote:
>>
>>             >>
>>             >>Hi Michel,
>>             >>
>>             >>On Wed, Aug 21, 2013 at 1:18 PM, Michel Wortmann
>>             >><wortmann at pik-potsdam.de>  wrote:
>>             >>...
>>
>>                 >>>
>>                 >>>As the r.watershed algorithm often leaves small
>>                 areas at the edges
>>                 >>>uncovered, you'll have to fill those before or
>>                 after patching, otherwise
>>                 >>>you'll have holes in your subbasin map.
>>
>>             >>
>>             >>... just curious: does this happen still in the latest
>>             GRASS 7 version?
>>             >>
>>             >>Markus
>>
>>
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>>
>>
>> -- 
>> Thomas E Adams, III
>> 718 McBurney Drive
>> Lebanon, OH 45036
>>
>> 1 (513) 739-9512 (cell)
>>
>>
> 
> 
> 
> 
> 
> 
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-- 
Stefan Lüdtke

Section 5.4-  Hydrology
Tel.: +49 331 288 2821
Fax: +49 331 288 1570
Email: sluedtke at gfz-potsdam.de

Helmholtz-Zentrum Potsdam
Deutsches GeoForschungsZentrum GFZ
(GFZ German Research Centre for Geoscience)
Stiftung des öff. Rechts Land Brandenburg
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