[gdal-dev] gdalwarp - dataset shifted several metres compared to arcgis

[jratike80]

Nicole Stoffels wrote
> Hi,
> 
> I am trying to reproject the CORINE 2012 dataset from LAEA (EPSG:3035) 
> to UTM 32 (EPSG:32632). I use the following command:
> 
> $ gdalwarp -overwrite -s_srs EPSG:3035 -t_srs EPSG:32632 -tr 100 100 
> -tap -dstnodata '-9999' g100_clc12_V18_5.tif corine2012_utm32n_test.tif
> 
> In the past years my colleague used ArcGIS for this operation, but since 
> we switched to Linux, I have to find a new solution. When I load the new 
> dataset generated with gdalwarp to QGIS and compare it with the old 2006 
> version built in ArcGIS, I have an offset of approximately 15m south and 
> 3m east for the single raster squares.
> 
> Now I am not sure if I simply forgot an important flag in my 
> gdalwarp-command or if the problem simply lies within ArcGIS (my 
> colleague used the standard options that were proposed).
> 
> Thank you for any ideas,

Shift is small, 15 and 3 meters, compared to the pixel size, 100 m. Anyway,
the reason for the difference is probably in where ArcGIS and GDAL decides
to place the origin when they warp the extents of the image. Target aligned
pixels can for sure shift the origin because that's why the option exists.
ArcGIS and GDAL may still compute the origin into slightly different places
if they do not use exactly same code for warping.

I would have a try by defining the output extents exactly with -te. But
first I would re-think if sub-pixel shifts are meaningful at all.

-Jukka Rahkonen-



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