[GRASS-user] Cut DEM by SHP

GRASS GRASS user
1

Hi to all....
I wanted to ask a question...
Is it possible to cut a raster (dem) through a shape or a vector?
Thanks..
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2

Salvator*eL*arosa wrote:

Is it possible to cut a raster (dem) through a shape or a vector?

If I understand correctly: (there are other 3D tools for planes)

g.region rast=MapName
v.to.rast

then either create a raster map named MASK (see r.mask) or
  r.mapcalc newmap='if(isnull(vect_mask), null(), MapName)'
                  # if( this , then do this, else do this )

Hamish

3

Hamish wrote:

Salvator*eL*arosa wrote:

Is it possible to cut a raster (dem) through a shape or a vector?

If I understand correctly: (there are other 3D tools for planes)

g.region rast=MapName
v.to.rast

then either create a raster map named MASK (see r.mask) or
  r.mapcalc newmap='if(isnull(vect_mask), null(), MapName)'
                  # if( this , then do this, else do this )

Hamish

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Thanks.
But with MASK is it not permanent?
while with r.mapcalc it's permanent map.

sorry my english!
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4

But with MASK is it not permanent?
while with r.mapcalc it's permanent map.

The mask will be in place as long as a raster map named "MASK" is there.
This affects maps that are read, not written.

for example: (spearfish dataset)

# will only save roads where the MASK is, as that is the only data read
r.mapcalc "MASK=if(isnull(fields))"
r.mapcalc test_rast=roads
g.remove MASK
d.rast test_rast

# will create map over entire region, regardless of MASK
r.mapcalc "MASK=if(isnull(fields))"
r.mapcalc "test_num = x() * y()"
g.remove MASK
d.rast test_num

in that way, MASK can have a permanent effect to newly written maps.

Hamish