[gdal-dev] ESRI's Mercator_Auxiliary_Sphere projection

[Patrick Lynn]

My application uses the GDAL & OGR libraries to load maps containing projection
metadata. As part of testing, I tried to load a GeoTIFF image exported from ESRI's
ArcMap 10.0 using the default coordinate system, the resulting OGRSpatialReference
does not validate successfully. Is there a way to get this to work?

Here is the output from gdalsrsinfo for such a dataset:

> ERROR 6: No translation for Mercator_Auxiliary_Sphere to PROJ.4 format is known.
>
> Validate Fails - contains non-standard PROJECTION[] values
>
> PROJ.4 : ''
>
> OGC WKT :
> PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
>     GEOGCS["GCS_WGS_1984",
>         DATUM["D_WGS_1984",
>             SPHEROID["WGS_1984",6378137.0,298.257223563]],
>         PRIMEM["Greenwich",0.0],
>         UNIT["Degree",0.017453292519943295]],
>     PROJECTION["Mercator_Auxiliary_Sphere"],
>     PARAMETER["False_Easting",0.0],
>     PARAMETER["False_Northing",0.0],
>     PARAMETER["Central_Meridian",0.0],
>     PARAMETER["Standard_Parallel_1",0.0],
>     PARAMETER["Auxiliary_Sphere_Type",0.0],
>     UNIT["Meter",1.0]]

It is quite possible that my application is not finding the appropriate
data files, but I didn't want to spend too much time investigating if this
projection is not yet supported.  I did notice that the defect described at
http://trac.osgeo.org/gdal/ticket/3962 has not been resolved, and then there's
the absence of an AUTHORITY clause in the WKT, so I'm thinking maybe this isn't
even doable.

Patrick