[Gdal-dev] processing SRTM-3?

Thom DeCarlo t.r.decarlo at LARC.NASA.GOV
Wed Jul 28 15:34:25 EDT 2004

Frank Warmerdam wrote:
> Thom DeCarlo wrote:
> > Oops, found another... issue. The SRTM documentation states that the
> > NODATA value is -32768 and the shell script accommodates that by
> > setting the appropriate value in the header file. However, it appears
> > that the rest of the gdal software assumes that the NODATA value is 
> > -9999. Is there any way to tell the gdal_translate program to change
> > any NODATA values it encounters to be -9999?
> Thom,
> The GDAL libraries should not assume a nodata value of -9999.  The data is
> being imported via the ESRI BIL format, right?  What does the .hdr file
> have for a NODATA value?  What does gdalinfo report about a dataset?
> Best regards,
> --

Unfortunately, I need to use geotiff format for the output terrain data and
I don't think geotiff has a defined NODATA value. One use of this terrain is
to feed a couple different 3D model builders and construct terrain models.
It seems that some of these tools fall back to a default NODATA value of 
-9999 for datasets that do not define their own value. That causes incorrect
interpretation of the -32768 value in the geotiff files as being valid data.

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