[GRASS-dev] r.external nodata problem

[Jamie Adams]

Hello all,

I'm having an issue where r.mapcalc is incorrectly detecting nodata when
using an r.external raster.  My basic work flow is something like this:

   - import raster using r.external
   - set the region to include a 1 pixel buffer around the image
   - run r.mapcalc with isnull to output nodata as 1.  The 1px buffer
   ensures that I get a single, continuous nodata region around the raster.

With certain r.external rasters, r.mapcalc is only returning nodata for the
first and last rows.  The first and last columns have the top and bottom
pixels (first and last row), but nothing else.

If I do the exact same routine with r.in.gdal, a continuous nodata region
around the raster is identified by r.mapcalc.

I reported this bug last year, but stopped seeing the problem and didn't
follow up.  Looks like it's still there, I'll attach some files for testing.

http://trac.osgeo.org/grass/ticket/369

- Jamie
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