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

Micha Silver tsvibar at gmail.com
Wed Apr 5 06:25:31 PDT 2017

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

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