[GRASS-user] Clipping rasters

[Hanlie Pretorius]

2010/8/10, Nikos Alexandris <nikos.alexandris at felis.uni-freiburg.de>:
> Hanlie Pretorius wrote:
>
>> I thought I created a clipped DEM by rasterising an irregular vector
>> boundary and then using a mask to create the clipped DEM from a
>> rectangular DEM.
>>
>> For example:
>> -----
>
> #first, check and set your region of interest
> g.region vect=border -pa

Tried this with the same result, as Jarek points out in the second
reply. So, I assume it's impossible to have a raster with an irregular
boundary in GRASS?

>
>> # convert vector border to raster
>> v.to.rast input="border" output="border" use="cat" type="area" layer=1
>> value=1 rows=4096                                |
>>
>> # set the mask to the raster border
>> r.mask border
>
>> # create the clipped DEM
>> r.mapcalc
>>
>> >dem_clipped=dem_full
>>
>> # remove the mask
>> r.mask -r
>> -----
>>
>> But it turns out I was wrong, the 'clipped' raster just contains NULL
>> values outside of the border raster. What did I do wrong? Is there a
>> better way to clip a raster to a vector boundary?
>
> So, always check the region ;-). I think this is the best (and only?) way to
> clip.
>
> Regards, Nikos
>