[gdal-dev] How to find correct 2D bounding box to subset in different CRS with gdal (different outputs for gdalwarp)?

[Andre Joost]

Hello Pham,

note that an EPSG:4326 rectangle of full degrees gets rotated and bended 
in almost any projected CRS (except Mercator).

Since the EPSG:32632 raster has to be an unrotated rectangle again, the 
corners of the projected EPSG:4326 rectangle are different from the 
corners of the EPSG:32632 rectangle. The difference will be filled with 
NODATA pixels.

Try to vsualize your problem in a GIS software like QGIS, and you see 
what I mean.

HTH,
Andre Joost

Am 21.11.18 um 16:33 schrieb Pham Huu Bang:
> Hello,
>
> I'm using GDAL version 1.11.4 and I have a problem how to use gdal to
> translate a bounding box correctly [Lat(62:63), Long(10:11)] from source
> CRS EPSG:4326 to target CRS EPSG:32632.
>
> I've tried so far with gdaltransform to translate coordinates: Long min,
> Lat min and Long max, Lat max (EPSG:4326) to E min, N min and E max, N Max
> (EPSG:32632) like this:
>
> gdaltransform -s_srs EPSG:4326 -t_srs EPSG:32632
>
> 10 61.9999999999999 0
> 552375.799656895 6874583.72713382
>
> 11 62.9999999999954 0
> 601293.020582477 6987164.64881585
>
> Then, I use these translated coordinates to create a bounding box in
> EPSG:32632 E(552375.799656895:601293.020582477),
> N(6874583.72713382:6987164.64881585) in EPSG:32632 for subsetting a 32632
> tiff file and then using gdalwarp the cropped result to EPSG:4326.
>
> The problem is the results of 2 cropped tiff files (both in EPSG:4326) are
> significantly different and I could not understand the reason (I think
> bounding box in EPSG:32632 are wrong but how to find the correct bounding
> box in EPSG:32632 from bounding box EPSG:4326)?
>
> 32632.tiff is a tiff file with grid size: 6820, 4632 and 4326.tiff is a
> file created by using gdalwarp -t_srs EPSG:4326 32632.tiff 4326.tiff with
> grid size: 8213, 2654.
>
>   Test 1:
>   # Subset on 32632 tiff by 32632 subset which are translated point by point
>   from 4326 subset
>   gdalwarp -te 552375.799656895 6874583.72713382 601293.020582477
>   6987164.64881585 32632.tiff subset_32632.tiff
>   Creating output file that is 1631P x 3753L.
>
>   # Warp cropped 32632 tiff file to 4326
>   gdalwarp -t_srs EPSG:4326 subset_32632.tiff subset_4326.tiff
>   Creating output file that is 3009P x 3070L.
>
>   Test 2:
>   # Subset 4326 on 4326 tiff file directly
>   gdalwarp -te 10 61.9999999999999 11 62.9999999999954 4326.tiff
>   subset_4326_org.tif
>   Creating output file that is 2019P x 2019L.
>
> Thanks,
>
>
>
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