[GRASS-user] Clipping Raster Map

Rich Shepard rshepard at appl-ecosys.com
Fri Jan 1 19:43:03 EST 2010

On Fri, 1 Jan 2010, Hamish wrote:

> please post the output of
> g.region -p

GRASS 6.4.0svn (Oregon):/usr4/grassbase/Oregon > g.region -p
projection: 99 (Lambert Conformal Conic)
zone:       0
datum:      nad83
ellipsoid:  grs80
north:      1334419.25160578
south:      1279151.24118496
west:       769192.9282895
east:       819255.92362222
nsres:      0.00175298
ewres:      0.00133118
rows:       31528020
cols:       37608092
cells:      1185708676737840

>  and
> r.info -gs $mapname

GRASS 6.4.0svn (Oregon):/usr4/grassbase/Oregon > r.info -gs map=dem

> how long are we talking about to render here, 2 seconds or 20?

   Well, after about 3 minutes it may move off 0% to 3%. After 5 or 6 minutes
I hit ^C to kill the process.

> g.copy only copies files*, it doesn't resample. if your base raster map
> is stored in PERMANENT or somewhere else in your mapset search path then
> there is usually little need to make a local copy, it will resample on
> the fly as needed, at full speed.. "copy" with r.resamp* or r.mapcalc
> if you want a new map which really is cropped

   The full span is stored in PERMANENTA. I want to work only with the
project area which is why I g.copy when I screw up the local copy.


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