[FWTools] gdal_translate, -a_srs, -a_ullr, and Projections with Rotations

[Even Rouault]

I've read very quickly what you want to do, so I might have not understood 
well. But here are a few hints :
* the spatial coordinates you give for each GCP must be consistant with the 
projection (you can set it with -a_srs if needed).
* You can't use -gcp and -a_ullr at the same time.
* After adding GCPs with gdal_translate, you can use gdalwarp to apply to 
rotation to the pixel data.

Le Wednesday 22 July 2009 19:59:28 Peter Willis, vous avez écrit :
> Hello,
>
> Well, I tried with GCPs but no UTM geography is applied to
> the output unless I supply the '-a_ullr' option. Using
> -a_ullr causes the GCPs to be ignored and the same pixel
> size calculation errors occur due to the rotation and
> the actual bottom right coordinates with respect to the
> upper left.
>
> gdal_translate appears to be calculating the pixel size
> based on the UL and LR corners, which is normal. However,
> with GCPs there should be more of a rotation/translation
> applied to the geography.
>
> Perhaps an option to override the pixel size calculations
> in each dimension should be added to the utility...
>
> Peter
>
> Peter Willis wrote:
> > Hello,
> >
> > I just noticed the '-gcp' option for gdal_translate.
> > It occurs to me that this should provide the required projection
> > adjustments.
> >
> > Peter
> >
> > Peter Willis wrote:
> >> Hello,
> >>
> >> I am applying geography to some UTM based images.
> >> The images have a 1.9 degree rotation.
> >>
> >> Is there a way to assign a rotation to the projection
> >> using gdal_translate?
> >>
> >> If not, is there a way to assign the rotation using
> >> any other GDAL tools?
> >>
> >> Thanks
> >>
> >> Peter
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