[GRASS-user] r.mask: no MASK created when using many categories

Mira Kattwinkel kattwinkel-mira at uni-landau.de
Wed Apr 5 06:59:43 PDT 2017

Dear Micha

thanks for your suggestion.

Actually, that's is what I usually do. However, I am not really 
interested in the catchment of the endpoints of the edges but in 
sampling points lying at the streams. If a point lies within the dem 
cell of the outlet, which can be a confluence of two streams, the 
coordinate approach will result in the catchment of both confluences, 
although the point lies just at one of them. That's why I came up with 
the idea of summing up the subcatchments of only the relevant branch of 
the stream network.

Maybe there are other thoughts on that?


On 05/04/17 15:25, Micha Silver wrote:
> On 04/05/2017 03:22 PM, Mira Kattwinkel wrote:
>> Dear List,
>> I am using r.mask to create a new raster map that only contains 
>> certain categories given in 'maskcats'. Then, I use r.mapcalc to save 
>> the map under a new name and (to be on the save side) delete the MASK 
>> with r.mask flag '-r'. I do this in a loop and it works fine until a 
>> case when the number of categories to combine is 213 (trail and error 
>> lead to 106 as the maximum number that works fine). Flag 'verbose' 
>> gives the message that a MASK was created, but none is there. The 
>> problem arises in both cases when I directly use Grass or through R 
>> using execGrass.
>> Is there a limit in the number of categories that can be passed to 
>> r.mask? I did not find any hint about that. Additionally, I wonder 
>> why there is no error message but in the contrary one that tells me 
>> that a MASK was created even when it failed.
>> In case the details are important (or if anybody has a better idea 
>> how to achieve what I want): I have a raster map of subcatchemts 
>> belonging to stream segments created with r.stream.basins. For the 
>> endpoints of segments, I want to combine these subcatchments to a 
>> total catchment raster map containing all upstream catchments.
> If you have the endpoint of of the outlet segment, you might use that 
> as the "coordinates" parameter to r.stream.basins to create a single 
> large drainage basin. Then use that as the mask to get out the 
> subcatchments.
>> Thanks a lot,
>> Mira
> -- 
> Micha Silver
> cell: +972-523-665918

Dr. Mira Kattwinkel
Quantitative Landscape Ecology
Institute for Environmental Sciences
University of Koblenz-Landau
Fortstra├če 7
76829 Landau
Phone: + 49 6341 280-31553
Office: Building I, Room 2.02

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