[Gdal-dev] rotations in Get/SetGeoTransform

[Frank Warmerdam]

Stephane Routelous wrote:
> I need to make a driver for GDAL, where the georeferencement of the image is
> defined in an XML file with the 4 corners of the image in decimal degrees.
> So, I need to transform those 4 points into this transformation matrix.
> 
> The other problem I have is that the image can be "stretched". Basically, it
> means that I can have the 4 points like :
> P1(0,0)
> P2(-2,2)
> P3(2,3)
> P4(4,1)
> 
> In this case, the image is not just rectangular and rotated anymore, because
> the angle between the x-axis an P1-P4 is different than the angle betwen the
> y-axis and P1-P2

Stephane,

The normal approach to this is to leave the GetGeoTransform() method defaulted,
and instead implement this as an image with 4 ground control points (GCPs).

Best regards,
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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