To Sebastian, Hi. You can get the towgs84 parameters you need from the EPSG database. The easiest way to do this is to use an authority factory to create a CRS from an EPSG code (31466 in your case). The returned CRS should have the towgs84 (BursaWolf) parameters included, which will be used to create the correct transformation.
An example of how to create a CRS from authority codes can be found in: http://svn.geotools.org/geotools/trunk/gt/demo/referencing/src/main/java/org/geotools/demo/referencing/CTSTutorial.java Note, Zone 3 of your projection is given in the command line example at the end of: http://geotools.codehaus.org/Coordinate+Transformation+Services+for +Geotools+2.1 so I expect that the EPSG database has the towgs84 parameters that you need. Rueben On Tue, 2006-12-12 at 04:18 -0800, Wegert wrote: > Hallo all, > > At the moment, I'm trying to project points, lines and polygons on "Google > Earth". To achieve this aim, I'm using GEOTOOLS. > > Now to the problem: > > As Martin Desruisseaux wrote in his answer ( > http://sourceforge.net/mailarchive/message.php?msg_id=15645183 ) you can't > set Hints.LENIENT_DATUM_SHIFT to Boolean.TRUE, if you want an accurate > transformation. > For example, the projection from GK2 (Gauß-Krüger 2) to WGS84 (as far as I > know this is the basis CRS of Google Earth) results in a deviation of about > 200 metres, always. (btw: You can take a look at the screenshot in the > attachment!) > > > > > Here are some informations about the transformation: > > sourcecrs: > > PROJCS["DHDN / Gauss-Kruger zone 2", > GEOGCS["DHDN", > DATUM["Deutsches_Hauptdreiecksnetz", > SPHEROID["Bessel 1841", 6377397.155, 299.1528128, > AUTHORITY["EPSG","7004"]], > AUTHORITY["EPSG","6314"]], > PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]], > UNIT["degree", 0.017453292519943295], > AXIS["Lon", EAST], > AXIS["Lat", NORTH], > AUTHORITY["EPSG","4314"]], > PROJECTION["Transverse_Mercator"], > PARAMETER["central_meridian", 6.0], > PARAMETER["latitude_of_origin", 0.0], > PARAMETER["scale_factor", 1.0], > PARAMETER["false_easting", 2500000.0], > PARAMETER["false_northing", 0.0], > UNIT["m", 1.0], > AXIS["x", EAST], > AXIS["y", NORTH], > AUTHORITY["EPSG","31466"]] > > > targetcrs: > > GEOGCS["WGS 84", > DATUM["WGS_1984", > SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]], > AUTHORITY["EPSG","6326"]], > PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]], > UNIT["degree", 0.017453292519943295], > AXIS["Lon", EAST], > AXIS["Lat", NORTH], > AUTHORITY["EPSG","4326"]] > > > > Result of System.out.println(transform): > > CONCAT_MT[INVERSE_MT[PARAM_MT["Transverse_Mercator", > PARAMETER["semi_major", 6377397.155], > PARAMETER["semi_minor", 6356078.962818189], > PARAMETER["central_meridian", 6.0], > PARAMETER["latitude_of_origin", 0.0], > PARAMETER["scale_factor", 1.0], > PARAMETER["false_easting", 2500000.0], > PARAMETER["false_northing", 0.0]]], > PARAM_MT["Molodenski", > PARAMETER["dim", 2], > PARAMETER["dx", 0.0], > PARAMETER["dy", 0.0], > PARAMETER["dz", 0.0], > PARAMETER["src_semi_major", 6377397.155], > PARAMETER["src_semi_minor", 6356078.962818189], > PARAMETER["tgt_semi_major", 6378137.0], > PARAMETER["tgt_semi_minor", 6356752.314245179]]] > > > As you can see, the translation parameters "dx", "dy", "dz" are equal to > "0.0". > > > The coordinates of the given point (highlighted in the screenshot) in GK2 > are: > > X: 2662992.3037465196 > Y: 5543456.129133454 > > > The results of GEOTOOLS for WGS84 are: > > X: 8.274064947588457 > Y: 50.00686449018631 > > > Though, the result has to be: > > X: 8.27317386543231; > Y: 50.0050926651181; > > I calculated this with "Postgres" and checked it visually and these are > nearly the correct coordinates ( < 2 metres)! > > > I need the general way for every kind of transformation from one chosen > coordinate system into WGS84...if it's possible. > > What should I set for the "BursaWolfParameter", which is required if I won't > set Hints.LENIENT_DATUM_SHIFT to Boolean.TRUE and how does it work? > > > I would be grateful for every response.... > Best regards > Sebastian > > http://www.nabble.com/file/4554/projection.JPG ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Geotools-gt2-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
