GeoTIFF documentation says you can use
ModelTransformationTag to define a transformation matrix, but later adds:
For Baseline GeoTIFF, the model space is always 2-D, and so the matrix will have the more limited form
And then goes on to describe a matrix that only supports 2D affine transformations.
Later in the document it seems to imply that non-affine projections are only supported via use of tiepoints, and still would not work with Baseline GeoTIFF images.
Case 5: The raster data cannot be fit into the model space with a simple affine transformation (rubber-sheeting required). Use only the ModelTiepoint tag, and specify as many tiepoints as your application requires. Note, however, that this is not a Baseline GeoTIFF implementation, and should not be used for interchange; it is recommended that the image be geometrically rectified first, and put into a standard projected coordinate system.
This seems to be confirmed in GDAL documentation, which describes
SetGeoTransform, which is used to "set the affine transformation coefficients".
Does that mean there is no way of describing non-orthorectified images using GeoTIFF?
Is there some non-baseline GeoTIFF that supports non-affine (i.e. projective transformations)? If so, what software supports it?
Is there any other image format that natively supports projective transformations?