[gdal-dev] gdalwarp produces all black output

[Even Rouault]

Le jeudi 08 août 2013 19:44:04, Hermann Peifer a écrit :
> 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.

Herman,

you're right. The issue was due to the input pixel size being very small. I've 
fixed that in ticket http://trac.osgeo.org/gdal/ticket/5190

Best regards,

Even

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