[gdal-dev] Warping without shear

[Joaquim Luis]

On 16-12-2011 15:32, Jan Hartmann wrote:
> Hi all,
>
> Is it possible to do a first order GCP-warp *without* shearing? I have 
> a rectangular scan with very imprecise control points, and I want it 
> georeferenced without any distortion. With a first order gdalwarp I 
> get back a map in the form of a parallellogram. Is there a way to get 
> back the original rectangular form? Control points will be way off, of 
> course, but I am interested in the original forms of the mapped items.
>

Jan,

What you want is to apply a transformation called (at least on the 
Matlab parlance) "Linear conformal" which an afine transform but without 
the the shear terms. Mirone has it implemented and if your image has the 
GCPS embedded the operation is really simple.

Joaquim
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