Hi All, I am trying to implement a warp from a latitude, longitude, altitude (LLA) image into a custom coordinate system using the GDAL Warp API. The transform between LLA and my coordinate requires scaling and shifting the elevation. My coordinate system is a local tangent plane on the Earth's surface where x is north, y is east, and z is pointed into the Earth.
When I follow the instructions in the GDAL Warp API tutorial <http://www.gdal.org/warptut.html>, my custom transform function supplied to "psWarpOptions->pTransformerArg <http://www.gdal.org/structGDALWarpOptions.html#a35647845a2629da876f379f82d58a2cd>" only receives input z=0 values. From the source code, it looks like the internal GDALWarpKernel only passes z=0 values to to the pTransformerArg. The Z values from the source elevation map are never used and therefore can never be re-projected. How can GDAL properly transform the source elevation data if the source elevation is never passed to the transform function? How are transforms between ellipsoids or elevation units performed if not through the GDALWarpOperation <http://www.gdal.org/classGDALWarpOperation.html> API? Thank you for any insights. -Adam Stambler
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