[mapguide-internals] Coordinate System question

[Jason Birch]

Hi all,

I'm playing around with the benchmarking data, which is apparently provided
in ETRS89, UTM31N.  .prj files were not included with the shape files, so I
looked up the EPSG code that Jeff was using in his WMS example (25831) at
http://spatialreference.org/ref/epsg/25831/ and got this back in a PRJ file:

PROJCS["ETRS89 / UTM zone
31N",GEOGCS["ETRS89",DATUM["D_ETRS_1989",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",3],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

I copied this file for each of the shape files, and moved on.

A bit later, when I was loading the shape files into MapGuide, I plugged the
above WKT into Maestro and clicked on Validate (which calls the MapGuide CS
lookup functions), and it came back with ETRF89.TM31, EPSG:3043, which
caught me by surprise.

So, I put the original EPSG code into Maestro, and after validation it came
back with ETRS89.UTM-31N, and the following WKT:

PROJCS["ETRS89.UTM-31N",GEOGCS["LL-ETRF89",DATUM["ETRF89",SPHEROID["GRS1980",6378137.000,298.25722210],TOWGS84[0.0000,0.0000,0.0000,0.000000,0.000000,0.000000,0.00000000]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["false_easting",500000.000],PARAMETER["false_northing",0.000],PARAMETER["central_meridian",3.00000000000000],PARAMETER["scale_factor",0.9996],PARAMETER["latitude_of_origin",0.000],UNIT["Meter",1.00000000000000]]

Are these equivalent?  Is the data on spatialreference.org correct?  Which
CS should I be using?

Thanks,
Jason