[gdal-dev] gdalwarp different results (vrt vs direct)

[Stefan Ziegler]

Hi

On Thu, Sep 3, 2015 at 10:58 AM, Even Rouault
<even.rouault at spatialys.com> wrote:
> This occurs in the middle of a source tile, or at the boundary between 2 tiles
> ?

In the middle of a source file.

> Just to be sure: you mean you are using the above -s_srs and -t_srs on one of
> the tile that makes the ortho2014.vrt ?

Yes.

> And what if you make a VRT with just that source image ?

I think it has nothing to do with the VRT. Using the gdalwarp command
on a single tif file it has the same breaking edge when using the -te
option. I did try the -et 0 option. Same error but not at the same
place (but only few pixels to the left) and much slower.

gdalwarp -overwrite -s_srs "+proj=somerc +lat_0=46.952405555555555
+lon_0=7.439583333333333 +ellps=bessel +x_0=600000 +y_0=200000
+units=m +k_0=1 +nadgrids=./chenyx06a.gsb" -t_srs "+proj=somerc
+lat_0=46.952405555555555 +lon_0=7.439583333333333 +ellps=bessel
+x_0=2600000 +y_0=1200000 +units=m +k_0=1 +nadgrids=@null"  -tr 0.125
0.125 -te 2611000 1233000 2612000 1234000 -co 'TILED=YES'
611233_12_5cm.tif 2611_1233_12_5cm.tif

I tried gdal_translate on the resulting image w/o the breaking edge
(w/o -te option):

gdal_translate -tr 0.125 -0.125 -projwin 2611000 1234000 2612000
1233000 2611_1233_12_5cm.tif out.tif

The resolution is perfect (=0.125) but the boundary is slightly
different (few centimeters). The requested area is partially outside
the image though.

> Any chance you can try with 2.0 or the dev version ?

I'm on dev version now.

You can find here the single tiff, the ntv2 grid shift file and to
shell scripts:
http://www.catais.org/tmp/gdalwarp/

best regards
Stefan