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

[Manuel Massing]

Hi Agustin,

> Please see the screenshot here:
> https://sites.google.com/site/filestemp2/home/error_georef.jpg?attredirects
> =0
> 
> We've tried polynomia of order 1 and 2 and Helmert, with very similar
> results. CRS is ED50 UTM31N
> 
> I've uploaded the input layer and points file to:
> https://sites.google.com/site/filestemp2/home/Ilerfly125v2.tif?attredirects
> =0&d=1
> https://sites.google.com/site/filestemp2/home/Ilerfly125v2.tif.points?attr
> edirects=0&d=1
> 

thanks for your test case.
I did a quick test reprojection, but couldn't see a problem with the
georeferencer output, i.e. the coordinates generated by the transform fit the 
destintaion coordinates within a few pixels, putting the max. error somewhere 
in the ballpark of 1.5m. This relies on the destination coordinates being in
ED50 UTM31N. The georeferencer has no support for transforming the
destination coordinates, so they need to be specified in the destination CRS.

I suspect the discrepancy you are seeing might be a problem with the
WGS84<->ED50 datum transformation, so it would be helpful if you could provide
the ArcGIS output as well. 

> Here you have an screenshot of the comparison to the same image
> georeferenced with ARCGIS (left)
> https://sites.google.com/site/filestemp2/home/errorgeorefARCG_QGIS.jpeg?att
> redirects=0&d=1
> https://sites.google.com/site/filestemp2/home/errorgeorefARCG_QGIS.jpegw?a
> ttredirects=0&d=1

I guess you meant to say that the right one is from ARCGIS?

cheers,

	Manuel
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