[GRASS-user] Cropping maps

[Vaclav Petras]

For cropping, see also a new addon module called r.clip which clips
according the computational region while respecting mask and the *original*
raster resolution:

https://grass.osgeo.org/grass72/manuals/addons/r.clip.html

Testing and feedback welcome.

Vaclav

On Tue, Sep 26, 2017 at 10:35 AM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:

> On 26/09/17 16:17, Moritz Lennert wrote:
>
>> On 26/09/17 15:57, Marco Alicera wrote:
>>
>>> Dear list,
>>> I am trying to crop a raster map into a smaller area, but I am failing.
>>>
>>> This wiki page link <https://grasswiki.osgeo.org/wiki/Cropping_maps> is
>>> quite clear:
>>> "Make boundary into mask using r.mask
>>> <https://grass.osgeo.org/grass72/manuals/r.mask.html> then copy raster
>>> source to new map (g.copy
>>> <https://grass.osgeo.org/grass72/manuals/g.copy.html>). All cells
>>> outside of the mask will be omitted from the new copy."
>>>
>>> r.mask vector=myarea
>>> g.copy --overwrite raster=OldRasterWithBigArea,NewRasterWithSmallArea
>>> r.mask -r
>>>
>>> I expected all cell outside were not going to be omitted, but replaced
>>> by NULL.
>>>
>>
>> I'm not sure I understand your last sentence, but AFAIK, the wiki info
>> is wrong. g.copy works directly on the files and ignores mask and region
>> settings. In your example, OldRasterWithBigArea and
>> NewRasterWithSmallArea should be strictly identical.
>>
>> You need to use r.mapcalc "new = old" while the mask is set to get a
>> raster with everything outside the mask set to NULL.
>>
>
> I've rewritten the wiki page to try to make things clearer.
>
>
> Moritz
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