[GRASS-dev] r.out.gdal, again

Markus Metz markus_metz at gmx.de
Wed Aug 20 16:02:07 EDT 2008

Dylan Beaudette wrote:
> On Wednesday 20 August 2008, Glynn Clements wrote:
>> Markus Metz wrote:
>>> r.out.gdal nodata handling could be changed so that the user has to
>>> provide a nodata value if there are NULLs in the raster, otherwise
>>> r.out.gdal aborts with an error.
>> That's reasonable for integer maps, but for FP maps it makes more
>> sense to simply default to NaN as the no-data value (the two are
>> essentially the same concept, so there is no information loss in using
>> NaN).
> Do other software packages understand 'Nan' ?
Do other file formats understand Nan? Reading a bit in GDAL API
documentation lets me suspect that NaN is not allowed, because for
GeoTIFF, you can specify a NoData value as in the current implementation
or you can add an internal mask, no mentioning of writing NaN for
Float32 or Float64 to a GDAL raster band. Did I overlook something?


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