[Gdal-dev] gdalwarp: target image extents are recognised wrong

[Michael84]

The region is about 80 km² and has the following coords:

UTM Zone 32:
UpperLeft:   482100 5887000
LowerRight:  490031  5877226

Should be the following in Lat/Long:
UpperLeft:    8° 43' 56.847'' E	53° 7' 55.587'' N
LowerRight:  8° 51' 4.683'' E		53° 2' 40.034'' N

Does this match your thoughts?


Frank Warmerdam-2 wrote:
> 
> Michael84 wrote:
>> Hello,
>> 
>> I'm using gdalwarp to warp an image of 15862P x 19548L from UTM to
>> Lat/Long.
>> 
>> gdalwarp -s_srs "+proj=UTM +zone=32 +datum=WGS84" -t_srs "+proj=latlong
>> +datum=WGS84" utm.tif latlong.tif
>> 
>> Gdalwarp then creates an image of 20491P x 15138L, instead of 15862P x
>> 19548L or something with the same apect ratio!!! What could be the reason
>> for it ?
>> 
>> I know that providing the target size is one solution to this problem,
>> but
>> it is not quite nice...
> 
> Michael,
> 
> If the region is large, my guess would be that the aspect ratio of your
> region is quite different in lat/long (ie. Plate Carree) than it is in
> UTM.  Even a small region relatively near the pole can exhibit substantial
> changes in aspect ratio in such a transformation.
> 
> 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    | President OSGeo, http://osgeo.org
> 
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> 

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