[gdal-dev] Re: GetProjectionRef() difference 1.8 vs 1.7.2

[Even Rouault]

Selon cobalto <scott.a.merritt at navy.mil>:


> These NITFs contain RPCs, so I mostly am unconcerned with the geotransform,
> exact or approximated. However, proper interpretation of the RPCs requires
> knowledge of the projection reference. In these cases, it seems somewhat
> circuitous to look for a projection reference among the GCPs. If
> GDALGCPsToGeoTransform() fails to return a geotransform, would there be any
> reason not to set the projection reference to the GCP projection (but to
> still have GetGeoTransform() return CE_Failure)? Is the dataset projection
> reference ever set to something different than the GCP Projection?

The current behaviour is consistant to the principles described in the GDAL Data
model page ( http://gdal.org/gdal_datamodel.html )

"""The coordinate system returned by GDALDataset::GetProjectionRef() describes
the georeferenced coordinates implied by the affine georeferencing transform
returned by GDALDataset::GetGeoTransform(). The coordinate system returned by
GDALDataset::GetGCPProjection() describes the georeferenced coordinates of the
GCPs returned by GDALDataset::GetGCPs().
Note that a returned coordinate system strings of "" indicates nothing is known
about the georeferencing coordinate system.
"""


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