[Qgis-developer] Georeferencer produces wrong (shifted) result

[Manuel Massing]

Hi Agustin,

> The points are correct (therefore the errors etc), but the
> georeferenced image is shifted. May be the datum is not taken into
> account
> when the georeferenced image is created.

I did a clean checkout, and could finally reproduce the problem:
it stems from the fact that your input file has a geotransform,
which flips the yaxis of the local coordinate system and changes the
origin. As the geotransform plugin does not handle geotransform
info correctly, this results in the shift you have observed.

Removing the geotransform (e.g. using "gdal_translate -co "PROFILE=BASELINE" -
of GTiff Ilerfly125v2.tif Ilerfly125v2-nogeotrans.tif") should give you
a file which the georeferencer can handle correctly (you may have to delete 
the accompanying .aux file, if gdal uses this to keep the geotransform).

I had a local patch in the georeferencer which handles geotransform
information, so this is why I couldn't reproduce the problem (talk about a
mixture of good and bad luck :-)). I will see what is required to make my
local changes ready for submission, so we can avoid such subtle problem with
georeferenced/pseudo-georeferenced files in the future. As I already
mentioned, due to an important deadline at work, I have little time to
dedicate to this atm, so it may take a few day... is there a release in the
pipeline?

cheers,

	Manuel

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