[GRASSLIST:2324] Re: Removing a section of a raster map

[Hal Mueller]

I haven't tried to do anything like this in a while, and might have 
the details a bit off, don't have time to pin it down right now.

I think the key is r.mask.  You can derive the mask by comparing 
layer with protrusion to layer without protrusion.  Or maybe just by 
looking at layer without protrusion.

(hip shot, untested!)

I would try

r.mapcalc
to make a binary raster, 1 where I want data and 0 where I don't

r.mask
set the mask to be that binary I just made

r.mapcalc newrast=rastwithprotrusion

g.remove rast=MASK

d.rast newrast
should display a correct layer

make sure to g.remove the mask (or use r.mask to set no mask) before testing
your new layer; otherwise you might just _think_ you got it right

Hal

----
Hal Mueller                hal at seanet.com
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