Hanlie Pretorius pisze:
2010/8/10, Nikos Alexandris <[email protected]>:
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
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raster is a matrix of values so it is always rectangular. Null is not a
value, NULL is lack of value. Irregular raster is a rectangural raster
with null (transparent) cells outside the border
J.
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