For reference, this has been submitted (and answered) here: http://lists.osgeo.org/pipermail/metacrs/2013-November/000749.html
Thanks On Wed, Nov 20, 2013 at 6:44 AM, Jody Garnett <[email protected]> wrote: > Next step is the spatial reference system crew at the MetaCRS project > (http://trac.osgeo.org/metacrs/). > Sign up and ask your question again. > > As I understand it this is a "meta" project - pulling together a lot of the > referencing projects (including PROJ) and tries to make sure we all "respect > the math" (tm) > -- > Jody Garnett > > On 20 November 2013 at 2:02:16 am, Christian Gendreau > ([email protected]) wrote: > > Thanks for you answer Jody. > > The PROJ.4 definition is : > +proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0 +k_0=0.99987742 +x_0=600000 > +y_0=2200000 +a=6378249.2 +b=6356515 +towgs84=-168,-60,320,0,0,0,0 > +pm=paris +units=m +no_defs > > So I'm using the same TOWGS84 parameter : TOWGS84[-168,-60,320,0,0,0,0] > http://spatialreference.org/ref/epsg/27572/ogcwkt/ > > So I have no idea what may be wrong. > > Thanks again, > > Christian > > On Mon, Nov 18, 2013 at 7:01 PM, Jody Garnett <[email protected]> > wrote: >> Well you have a small clue, that "lenient" is used when the two coordinate >> systems use a different model for the shape of the earth, so no correct >> transformation exists between the two systems. Indeed we can see that, in >> the definition. >> >> So you are not doing anything wrong, question is what do you want to do? >> You >> are going to have to make an assumption on how to do the DATM shift, but >> what assumption do you want to make? Sounds like you would like to make >> the >> same assumption as PROJ.... >> >> Check what PROJ is doing and copy their "+towgs84" parameters when >> constructing your WKT by hand. >> >> Jody >> >> Jody Garnett >> >> >> On Tue, Nov 19, 2013 at 5:41 AM, Christian Gendreau >> <[email protected]> wrote: >>> >>> Hi, >>> >>> I'm trying to convert/transform some coordinates from one CRS to >>> another using JTS.transform(...) >>> There is a difference in what GeoTools 10 returns and what PostGIS and >>> QGIS return. >>> I'm aware that the parameters used by GeoTools are from the EPSG >>> database and are not managed by GeoTools but I'm having an issue when >>> I provide the exact WTK. >>> >>> Input is in EPSG:27572 (Lambert zone II) >>> ------- >>> CoordinateReferenceSystem sourceCrs = CRS.decode("EPSG:27572"); >>> CoordinateReferenceSystem targetCrs = DefaultGeographicCRS.WGS84; >>> >>> Coordinate coord = new Coordinate(605937.033, 2426318.714); >>> Point sourcePoint = geometryFactory.createPoint(coord); >>> MathTransform transform = CRS.findMathTransform(sourceCrs, targetCrs); >>> Geometry targetGeometry = JTS.transform( sourcePoint, transform); >>> ------- >>> >>> This will not work except if I use the 'lenient' flag and then I will >>> get: >>> POINT (2.4180555600606395 48.832161511178725) >>> This is 400 meters offset but there is no TOWGS84 parameters provided >>> so I'm don't know what accuracy to expect. >>> >>> So I tried with PostGIS 2.0.1 and I got : POINT(2.41733554398175 >>> 48.8352090484985) >>> This is correct. >>> >>> Then, I tried to use the PostGIS WTK definition in GeoTools. >>> >>> crs = CRS.parseWKT("PROJCS[\"NTF (Paris) / Lambert zone >>> II\",GEOGCS[\"NTF >>> >>> >>> (Paris)\",DATUM[\"Nouvelle_Triangulation_Francaise_Paris\",SPHEROID[\"Clarke >>> 1880 >>> >>> (IGN)\",6378249.2,293.4660212936265,AUTHORITY[\"EPSG\",\"7011\"]],TOWGS84[-168,-60,320,0,0,0,0],AUTHORITY[\"EPSG\",\"6807\"]],PRIMEM[\"Paris\",2.33722917,AUTHORITY[\"EPSG\",\"8903\"]],UNIT[\"grad\",0.01570796326794897,AUTHORITY[\"EPSG\",\"9105\"]],AUTHORITY[\"EPSG\",\"4807\"]],UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]],PROJECTION[\"Lambert_Conformal_Conic_1SP\"],PARAMETER[\"latitude_of_origin\",52],PARAMETER[\"central_meridian\",0],PARAMETER[\"scale_factor\",0.99987742],PARAMETER[\"false_easting\",600000],PARAMETER[\"false_northing\",2200000],AUTHORITY[\"EPSG\",\"27572\"],AXIS[\"X\",EAST],AXIS[\"Y\",NORTH]]"); >>> >>> and I got: POINT (2.183603198566145 48.8352075151015) >>> which is 17 km offset. >>> >>> Does anyone know what I'm doing wrong? >>> >>> Thanks, >>> >>> Christian Gendreau >>> >>> >>> >>> ------------------------------------------------------------------------------ >>> Shape the Mobile Experience: Free Subscription >>> Software experts and developers: Be at the forefront of tech innovation. >>> Intel(R) Software Adrenaline delivers strategic insight and game-changing >>> conversations that shape the rapidly evolving mobile landscape. 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