In trying to troubleshoot why the same data as a geoserver wms and 
postgis vector were shifted relative to one another, I picked up that 
they are projecting differently (26331 to 3875):

input point example:

"SRID=26331;POINT(542053.551 787930.307)"

in postgis (2.0):

"SRID=3857;POINT(376265.240380565 795675.534596811)"

in geoserver (2.2-SNAPSHOT):

"SRID=3857;POINT(376271.1415793335 790368.2841989407)"

proj4 text that postgis uses:

  +proj=utm +zone=31 +ellps=clrk80 +towgs84=-92,-93,122,0,0,0,0 +units=m 
+no_defs


The WKT parameters that geoserver users:

I can't find them...I tried to follow these instructions 
http://docs.geoserver.org/latest/en/user/advanced/crshandling/manualepsg.html 
but they appear to be out of date since instead of EPSG.sql there is now 
EPSG.zip containing EPSG.script, EPSG.properties and EPSG.data. The 
latter which probably contains the projection definitions is binary.


postgis WKT for comparison:

  PROJCS["Minna / UTM zone 
31N",GEOGCS["Minna",DATUM["Minna",SPHEROID["Clarke 1880 
(RGS)",6378249.145,293.465,AUTHORITY["EPSG","7012"]],TOWGS84[-92,-93,122,0,0,0,0],
AUTHORITY["EPSG","6263"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4263"]],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],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],AUTHORITY["EPSG","26331"],AXIS["Easting",
EAST],AXIS["Northing",NORTH]]

Any ideas which definition or transformation engine might be wrong?

-- 
regards

Gavin

Gavin Fleming
http://afrispatial.co.za
t: 0218630660
c: 0845965680
f: 0866164820


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