[GRASS-user] cutting issue (again): r.mapcalc vs. r.resample

Achim Kisseler ak7 at jupiter.uni-freiburg.de
Mon Jan 25 17:44:30 EST 2010

And more:

...The category values in the new raster output map layer will be the 
same as those in the original, except that the resolution and extent of 
the new raster output map layer will match those of the current 
geographic region settings (see g.region)....



Tim Michelsen schrieb:
> Hello,
> I while ago I asked how to cut a small map from a larger one using the
> region settings as boundary for the small map:
> http://n2.nabble.com/r-mapcalc-changes-color-table-td4072836.html#a4072836
> I tried this again:
> Approach 1: r.mapcalc
> 	r.mapcalc "cut=if(boundary_raster, large_map,
> null())"
> Approach 2: r.resample
> 	r.resample input=large_map output=cut
> I notice the that using Approach 2, the areas that was outside the set
> region is white. The underlayung rasters are not visible (or only if I
> set the opacity of "cut" to a low value).
> If I use Approach 1 with r.mapcalc, the areas outside the region are
> really NULL() (=transparent) and underlaying larger rasters are visible.
> Only that the result "cut" from r.mapcalc has a new colortable.
> Am I doing something wrong?
> Why is the no such command r.cut?
> Thanks in advance for your help,
> Timmie
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