[gdal-dev] losing elevation data

Frank Warmerdam warmerdam at pobox.com
Wed Aug 19 09:58:40 EDT 2009

Devrim Baris Acar wrote:
> Hi,
> I am a newbie on gdal and gis so forgive me.
> I have downloaded the geotiff elevation data  srtm30.7z from 
> http://worldwind28.arc.nasa.gov/public/WorldWindWMS/ . The file contains 
> elevation data for the globe. I want to change a a geotiff file from 
> this set to bil file format(hoping to use it in worldwind).
> I use;
> gdal_translate -of EHdr e020n40.Bathmetry.tif deneme.bil
> It completes translation with no errors but when I open the file in free 
> tool ER Viewer it is pure black and white while the original contains 
> tones of gray.
> It seems to have loss the granularity of data.


It looks like the source data is too large for me to practically download
and try.  Is one TIFF file (such as e020n40.Bathmetry.tif) more reasonable
sized?  Perhaps you could make it available for me to try?

The translation approach looks fine, but there is some lack of clarity in
how floating point vs. integer BIL files should be distinguished.  It may
be that ERViewer produces different results than ought to be the case.
You might want to try a GDAL based viewer such as OpenEV or QGIS on the
BIL dataset to see if it looks ok.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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