Conversion of GTOPO30

[Jason Sperfslage]

Hi Stephan,

Perhaps your problem more complicated than I think, but here is what I have
done in similar situations:

1) Import each image independently, just use the original resolution and region
   for each one.
2) Now edit your region to the be entire area of interest and the final 
   resolution of interest.
3) Use r.mapcalc to merge the images together into the new window/resolution.

   g.region region=big.region
   r.mapcalc "newimage1 = gtopoimage1"
   r.mapcalc "newimage2 = gtopoimage2"
   r.mapcalc "bigimage = max(newimage1,newimage2)"

It's been some time since I've done this, so maybe/maybe not - it should only
take a minute or two to test it.  You could probably even skip the separate
resamplings of gtopoimage*, and just do the "max" on them directly.  I don't
know if you need more elaborate sampling than this, but both images are gridded
rasters, you shouldn't need to go to points and then surf the points together - 
I know how slow that can be!  When you redefine a raster with r.mapcalc it will
resample to the resolution of the currently defined region.  You can use this
to sample up to a coarser resolution too, if you don't mind having point samples
from the original data.


Hope this helps - let me know.


Best regards,

Jason

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  Jason A. Sperfslage                     Hydrologic Research Center
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