[Gdal-dev] NITF ICHIPB Extension?

[Frank Warmerdam]

On Fri, 10 Dec 2004 14:26:42 -0500, William Lyons
<wlyons at prologic-inc.com> wrote:
> I agree.  But, the chips I'm working with are rotated.  Which leads me
> to another question about the geo-transform.  I'm assuming that the
> values at indices 2 and 4 are how I would define a rotation.  My
> assumption is that the value at index 2 is a ratio of change in x as
> line increases and the value at index 4 is a ratio of change in y as
> pixel increases.  Please tell me I'm wrong and there's an easier way so
> I don't have to calculate these for a rotated chip.

William,

Yes, that is correct, at least roughly. 

I would suggest you just derive corner GCPs and then use the
GDALGCPsToGeoTransform() to compute the correct geotransform. 

  http://www.gdal.org/gdal_8h.html#a86

Best regards,
-- 
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