Re: [Geotools-gt2-users] CRS transformation not accurate

[Martin D. <mar...@no...>]

Lo=EFc MAZE a =E9crit :
> The only data which can be interesting is about the transformation : NT=
F=20
> =3D> WGS84. I don't know if it is useful for Geotools or not.

The following command line:

java -classpath gt2-epsg-access-2.3-SNAPSHOT.jar=20
org.geotools.referencing.factory.epsg.DefaultFactory 4275

show the following:

GEOGCS["NTF",
   DATUM["Nouvelle Triangulation Francaise",
     SPHEROID["Clarke 1880 (IGN)", 6378249.2, 293.4660212936269, AUTHORIT=
Y["EPSG","7011"]],
     TOWGS84[-168.0, -60.0, 320.0, 0.0, 0.0, 0.0, 0.0],
     AUTHORITY["EPSG","6275"]],
   PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
   UNIT["degree", 0.017453292519943295],
   AXIS["Geodetic latitude", NORTH],
   AXIS["Geodetic longitude", EAST],
   AUTHORITY["EPSG","4275"]]

So its look like that a TOWGS84 element is defined for EPSG:4275, but not=
 for EPSG:27572 (even if=20
they use the same spheroid - EPSG seems to still consider them as two dif=
ferent datum, not sure why).

You may try the following:

     FactoryFinder.getCRSFactory(null).parseWKT(wkt);

where wkt is:

PROJCS["NTF (Paris) / Lambert zone II",
   GEOGCS["NTF (Paris)",
     DATUM["Nouvelle Triangulation Francaise (Paris)",
       SPHEROID["Clarke 1880 (IGN)", 6378249.2, 293.4660212936269, AUTHOR=
ITY["EPSG","7011"]],
       TOWGS84[-168.0, -60.0, 320.0, 0.0, 0.0, 0.0, 0.0],
       AUTHORITY["EPSG","6807"]],
     PRIMEM["Paris", 2.5969213, AUTHORITY["EPSG","8903"]],
     UNIT["grade", 0.015707963267948967],
     AXIS["Geodetic latitude", NORTH],
     AXIS["Geodetic longitude", EAST],
     AUTHORITY["EPSG","4807"]],
   PROJECTION["Lambert Conic Conformal (1SP)", AUTHORITY["EPSG","9801"]],
   PARAMETER["central_meridian", 0.0],
   PARAMETER["latitude_of_origin", 52.0],
   PARAMETER["scale_factor", 0.99987742],
   PARAMETER["false_easting", 600000.0],
   PARAMETER["false_northing", 2200000.0],
   UNIT["m", 1.0],
   AXIS["Easting", EAST],
   AXIS["Northing", NORTH],
   AUTHORITY["EPSG","27572"]]

i.e. the output of java [...] DefaultFactory 27572 with the TOWGS84 eleme=
nt copied from java [...]=20
DefaultFactory 4275. I'm really not sure that it is okay; lets see if the=
 output is better.

	Martin.