[GRASS-user] interpolate raster map

Nikos Alexandris nikos.alexandris at felis.uni-freiburg.de
Thu May 22 07:23:39 EDT 2008

On Thu, 2008-05-22 at 13:14 +0200, Rainer M Krug wrote:
> Hi
> I have two raster maps, one (mapA) based on a raster map of a much
> lower resolution (see attached picture) and the other one is in the
> MASK (pink). I would like to do two things:
> 1) "smooth" mapA, so that it is not as grainy as it is now. I know
> that that will introduce error, but the error will be less important
> then the edges based on the coarser resolution.
> 2) extrapolate to the areas not covered by mapA, but part of MASK.
> again - I am aware that this will introduce considerable error, but
> the same applies as in the previous case. So what I would like to do
> here, is essentially fill the edges with the values of the adjacend
> cells which have values.
> Any ideas how I can achieve this?
> I looked at resampling (for (1)), but it increases the edge without
> data, which is not acceptable for me.
> Thanks a lot,
> Rainer

Hi Rainer.

About 1:

The r.resamp module uses the nearest neighbour method which will not
"smooth" your map.
Have a look at r.resamp.interp
( http://grass.osgeo.org/grass63/manuals/html63_user/r.resamp.interp.html )
and I think the bicubic method should help.

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