[gdal-dev] Problems with large ASTER GeoTIFF

[Etienne Tourigny]

On Mon, Apr 14, 2014 at 11:16 AM, Nicole Stoffels <stoffels at f2e.de> wrote:

> 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.


You need to set the compression options on any gdal command, it does not
use the compression of the input file. Also, you specifically asked for no
compression, so it's doing what you told it to.
use "-co COMPRESS=LZW"


> 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.
>

try without changing the extents and see if a single command (as suggested
by Jean-Luc) works



>
> 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.
>

your input values are probably between 0 and 1 in this case


>
> 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
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