[GRASS-user] .e00 to DEM

[Dylan Beaudette]

On Wednesday 08 July 2009, Nikos Alexandris wrote:
> There is something strange with the values though (they expand from min
> = -32687  max = 32645). Don't have the time to dig further, maybe there
> are details in the meta-data about it (!?).

This looks like an overflow problem. Could it be that this file contains 
unsigned 16 / 32 bit integers, but is being read in as signed 16 bit 
integers?

This used to happen when reading in Arc ASCII grids that contained very large 
numbers (> 32768) somewhere other than in the first couple of lines. I am 
pretty sure this bug has been fixed-- but I am not sure how GDAL is 
interpreting this specific file. It would be useful to use gdal_translate to 
copy the file, forcing the bit-size of the output to something else.

Here was the original GRASS ticket: http://trac.osgeo.org/grass/ticket/166
and the subsequent GDAL ticket: http://trac.osgeo.org/gdal/ticket/2369

There are some tips in the GDAL ticket on forcing a file to be read as a 32bit 
integers (etc.). Quoth Frank W:

Note that with gdal_translate you can convert pixel types on the fly, so if 
you know the data range is suitable for Int16, you could 
do "gdal_translate -ot Int16 in.grd out.tif" for instance.

Cheers,
Dylan



-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341