[Gdal-dev] gdalwarp, using GCPs with pixel positions outside the input image

[Frank Warmerdam]

Chris Campbell wrote:
> So my question is, does using GCPs with pixel positions outside the 
> image to be warped screw up the transformation?
> Thanks for any comments....

Chris,

I think your approach is correct and the problem is likely due to
inaccuracies and differing round-off errors in the polynomial calculation
code.  What order polynmomial are you using?   In general I am not impressed
with the numerical quality of the GDAL polynomial solver and transformer.

I'm not really sure why you need to do things in chunks though.  GDAL warp
is intended to be usable for large images, and I have personally processed
images up to 40GB without any apparent issues other than that it takes quite
a while.  It should scale up to hundreds of GB images at least.

Best regards,
-- 
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