[gdal-dev] gdalwarp produces all black output

[Hermann Peifer]

On 2013-08-08 9:55, ludwig.hilger wrote:
> Hello everybody,
>
> I am also a newbie and seem to have a similar problem, but cannot get it
> solved. I am trying to reproject the following file:
> http://www.altmuehlnet.de/~hilger/Test_Smooth_0208_4258.tif
> I am using the following line:
> gdalwarp -et 0 -r bilinear -s_srs EPSG:4258 -t_srs EPSG:25832
> Test_Smooth_0208_4258.tif Test_Smooth_0208_4258_25832.tif

I downloaded your test file and noted that it has 10000x10000 pixel and 
a real world extent of around 7x7 metres. So 1 pixel in your GeoTIFF 
represents less than 1x1 mm. I can only blindly assume that some 
rounding effects related to the small pixel size lead to the problem you 
observed. I noted the same problem in my testing (I am using the MacPort 
of GDAL 1.10, on my MacBook).

I re-defined the extent of your file to 1x1 degree and was able to warp 
the resulting file without any problem:

$ gdal_translate Test_Smooth_0208_4258.tif out_1x1.tif -a_ullr 10 47 11 46

$ gdalwarp out_1x1.tif out_25832.tif -t_srs epsg:25832 -et 0 -rb

Maybe someone from the GDAL devs has an explanation for this behaviour.

Hermann