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

[Michel Wortmann]

Thanks Markus and Stefan,
that did make a difference but I think it will always be a bit of a 
gamble and a gap filling to match both the catchment with its subbasins 
will always be needed.
R,
Michel

On 02/20/2014 10:09 PM, Markus Metz wrote:
> On Thu, Feb 20, 2014 at 8:25 PM, Stefan Lüdtke <sluedtke at gfz-potsdam.de> wrote:
>> 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.
> This is correct, r.watershed need a buffer of at least one cell around
> the catchment, otherwise it can not find out where exactly the
> catchment's borders are.
>
> Markus M
>
>
> 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
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>>
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