[Proj] Using a GDAL-generated NTV2-file

Jan Hartmann j.l.h.hartmann at uva.nl
Sat May 28 14:18:44 EST 2011

On 05/24/11 15:18, Frank Warmerdam wrote:
> Ah, it's gdal_grid generated.  I had assumed it's habit of producing
> south-up files would have been corrected by now.  It isn't a program
> I've had any real input on.
> gdalwarp does a rectification to north up.  In a regular case like this
> it should just amount to a mirroring but you might want to inspect it a
> bit to be sure the corners are still the same, etc.
> The proof will be in the pudding - if you get the right transformation.
Yes, the results look correct: after doing "gdal_grid" and mirroring the 
result with a simple "gdalwarp" without parameters, the data are in the 
correct position (i.e. unmirrored). Why is this gdalwarp-step needed? Is 
this a bug?

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