[GRASS-user] Incorrect x and y shift values for Alaska State Plane Zone 1 (omerc)

[fbiles]

Hello List,

While I am old to GIS, I am very new to the GRASS world.
I am running GRASS 6.4.3C2 for Windows and have added a raster DEM (GeoTIFF)
map layer.  The DEM originated from ArcGIS with the projection defined as:

/Projection: Hotine_Oblique_Mercator_Azimuth_Natural_Origin
False_Easting: 5000000.000000
False_Northing: -5000000.000000
Scale_Factor: 0.999900
Azimuth: -36.869898
Longitude_Of_Center: -133.666667
Latitude_Of_Center: 57.000000
Linear Unit: Meter (1.000000)

Geographic Coordinate System: GCS_North_American_1983
Angular Unit: Degree (0.017453292519943295)
Prime Meridian: Greenwich (0.000000000000000000)
Datum: D_North_American_1983
  Spheroid: GRS_1980
    Semimajor Axis: 6378137.000000000000000000
    Semiminor Axis: 6356752.314140356100000000
    Inverse Flattening: 298.257222101000020000/

This should be equivalent to EPSG 26931, or in PROJ4 lingo:
+proj=omerc +lat_0=57 +lonc=-133.6666666666667 +alpha=323.1301023611111
+k=0.9999 +x_0=5000000 +y_0=-5000000 +ellps=GRS80 +datum=NAD83 +units=m
+no_defs 

What puzzles me, is that in GRASS, *g.proj -p* for the layer returns:
-PROJ_INFO-------------------------------------------------
name       : Oblique Mercator
proj       : omerc
datum      : nad83
ellps      : grs80
lat_0      : 57
lonc       : -133.6666666666667
alpha      : 323.1301023611111
k          : 0.9999
x_0        : 0
y_0        : 0
gamma      : 323.1301023611111
no_defs    : defined

The values for x_0 and y_0 are zero instead of 5000000 and -5000000.

Can anyone explain to me what is happening here? Is this a bug?  If not, how
do I get GRASS to define the projection correctly?

Thank you for any help,
Frances



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