gdal incorrectly reads projection of ArcView rasters having U.S. survey feet

[warmerdam]

(Transferred from bugzilla)

ArcView rasters whose units are U.S. Survey Feet are erroneously reported by GDAL as having international feet.

The procedure used to retrieve the projection is using the Python GDAL bindings as follows:

gd = gdal.Open("c:/rastername/w001001.adf")
gd.GetProjection()

Note that the great majority of State Plane coordinate system use U.S. Survey feet rather than the international foot, and the difference is noticable. The problem appears to arise when GDAL interprets the prj.adf file in the raster.

Following is an example prj.adf for California Zone 6, which uses the U.S. survey foot.

Projection    STATEPLANE
Fipszone      406
Datum         NAD83
Spheroid      GRS80
Units         FEET
Zunits        NO
Xshift        0.0
Yshift        0.0
Parameters    

ArcView reports the raster having the above prj.adf as being in the the U.S. Survey Foot. It turns out that when Units are called out as FEET in the prj.adf file, this always means U.S. Survey Foot, not the international foot.

When the international foot is the unit, the prj.adf file supplies the number of feet per meter e.g.

Units         3.280839895013123

(That last number equals 1/0.3048 in case I typed it in wrong)

I have done many experiments with ArcView to check this, creating custom projections, and changing the units between feet and international feet, and ArcView is consistent. FEET always means the U.S. Survey foot in the prj.adf file.