[gdal-dev] Problems with large ASTER GeoTIFF

[Nicole Stoffels]

Dear Gdal-List,

I have a large ASTER file (downloaded from 
http://www.eea.europa.eu/data-and-maps/data/eu-dem#tab-european-data) in 
the GeoTIFF-format. It is compressed with LZW. What I want to do is:

1. unpack it
2. seperate a smaller region from it
3. convert this regional GeoTIFF to a PNG

What I am doing:

$ gdal_translate -co COMPRESS=NONE EUD_CP-DEMS_6500035000-AA.tif tmp1.tif

$ gdal_translate -srcwin 6500 3300 1000 1000 tmp1.tif tmp2.tif

$ gdal_translate -of PNG tmp2.tif tmp2.png

When I display the info with gdalinfo the first step seems to produce a 
decompressed file. The line COMPRESSION=LZW is not there anymore. 
However, if I want to display the min and max with gdalinfo, I get the 
following error.

ERROR 1: Failed to compute min/max, no valid pixels found in sampling.

I thought that the file might be too large, but if I change the 
data_type from float 32 to e.g. Int16 I get 0 as min and max value. 
That's why I assume that already the first gdal_translate does not work 
as I actually want it to work.

The other two transformations work without error messages. However, in 
the end I get a black png.

I have tried all types of transformation with various options. But as I 
am new in the subject and do not know much about gdal, I have no further 
ideas how to generate a file from my large GeoTIFF to continue working with.

I hope someone has an idea, what's going wrong with my 
gdal_translations. Thanks very much in advance.

Best regards
Nicole