you can add a TOWGS84 as per the example below - hope this helps
private static final String OSGBWKT="PROJCS[\"OSGB 1936 / British National
Grid\", \n" +
" GEOGCS[\"OSGB 1936\", \n" +
" DATUM[\"OSGB_1936\", \n" +
" SPHEROID[\"Airy 1830\", 6377563.396, 299.3249646], \n" +
" TOWGS84[375,-111,431,0,0,0,0]], \n" +
" PRIMEM[\"Greenwich\", 0.0], \n" +
" UNIT[\"degree\", 0.017453292519943295], \n" +
" AXIS[\"Lon\", EAST], \n" +
" AXIS[\"Lat\", NORTH]], \n" +
" PROJECTION[\"Transverse_Mercator\",
AUTHORITY[\"OGC\",\"Transverse_Mercator\"]], \n" +
" PARAMETER[\"central_meridian\", -2.0], \n" +
" PARAMETER[\"latitude_of_origin\", 49.0], \n" +
" PARAMETER[\"scale_factor\", 0.9996012717], \n" +
" PARAMETER[\"false_easting\", 400000.0], \n" +
" PARAMETER[\"false_northing\", -100000.0], \n" +
" UNIT[\"m\", 1.0], \n" +
" AXIS[\"x\", EAST], \n" +
" AXIS[\"y\", NORTH] \n" +
" ]";
John Grange
Senior Software Engineer
Tel: +44 (0)1749 834922
email: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
BlueFinger Limited
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-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Bernd Resch
Sent: Tuesday, December 13, 2005 12:31 PM
To: geotools-gt2-users@lists.sourceforge.net
Subject: [Geotools-gt2-users] coordinate transformation with additional
Bursa-Wolf parameters.
Hello,
1.) I've implemented a coordinate transformation service using GeoTools
2.1 shown in the following code. It converts different CRSs to WGS84_3.
Now, if I want to transform a point from "Gauß-Krüger 31", which is an
Austrian CRS (EPSG:31295) using the Bessel 1841 ellipsoid, several
Bursa-Wolf parameters have to be added. How can this be done using
GeoTools 2.1?
2.) I also tried to tackle this problem with GeoTools 2.2 M2 by using
the class "GeocentricTranslation". I also posted my (perhaps completely
wrong) code below. Can I anyhow just incorporate the Bursa-Wolf
parameters into my ordinary transformation service (s. ad 1.))? Or can't
that be achieved by creating a CRS from a WKT?
ad 1.)
public static DirectPosition transformCoords(double x_co, double y_co,
String sCRS)
{
CoordinateReferenceSystem sourceCRS = null;
CoordinateReferenceSystem targetCRS = null;
MathTransform math = null;
DirectPosition2D aPosition = new DirectPosition2D(x_co, y_co);
DirectPosition transformedDP = null;
try
{
CRSFactory crsFactory = FactoryFinder.getCRSFactory(null);
String sourceWKT = CRSFromWKTCreator.generateWKT(sCRS);
String targetWKT = "GEOGCS[\"WGS
84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS
84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.01745329251994328,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]]";
sourceCRS = crsFactory.createFromWKT(sourceWKT);
targetCRS = crsFactory.createFromWKT(targetWKT);
DirectPosition2D transformedPos = new DirectPosition2D();
math = CRS.transform(sourceCRS, targetCRS, true);
transformedDP = math.transform(aPosition, null);
}catch(NoSuchAuthorityCodeException nsace){nsace.printStackTrace();}
catch(FactoryException
fe){fe.printStackTrace();}catch(TransformException
te){te.printStackTrace();}
return transformedDP;
}// transformCoords
ad 2.)
public static DirectPosition transformCoords(double x_co, double y_co,
String sCRS)
{
CoordinateReferenceSystem sourceCRS = null;
MathTransform math = null;
DirectPosition2D aPosition = new DirectPosition2D(x_co, y_co);
DirectPosition transformedDP = null;
try
{
CRSFactory crsFactory = FactoryFinder.getCRSFactory(null);
String sourceWKT = CRSFromWKTCreator.generateWKT(sCRS);
String targetWKT = "GEOGCS[\"WGS
84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS
84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.01745329251994328,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]]";
sourceCRS = crsFactory.createFromWKT(sourceWKT);
DefaultGeographicCRS geoCRS =
org.geotools.referencing.crs.DefaultGeographicCRS.WGS84;
DefaultCartesianCS cartCS =
org.geotools.referencing.cs.DefaultCartesianCS.PROJECTED;
final CoordinateReferenceSystem targetCRS =
crsFactory.createFromWKT(targetWKT);
final BursaWolfParameters toWGS84 = new
BursaWolfParameters(DefaultGeodeticDatum.WGS84);
toWGS84.dx = 577.326;
toWGS84.dy = 90.129;
toWGS84.dz = 463.919;
toWGS84.ex = 5-137;
toWGS84.ey = 1.474;
toWGS84.ez = 5.297;
toWGS84.ppm = 2.4232;
GeocentricTranslation geoTrans = new GeocentricTranslation(toWGS84);
GeneralDirectPosition fromPos = new
GeneralDirectPosition(x_co,y_co);
GeneralDirectPosition toPos = new GeneralDirectPosition(targetCRS);
transformedDP = geoTrans.transform(fromPos,toPos);
}catch(NoSuchAuthorityCodeException nsace){nsace.printStackTrace();}
catch(FactoryException
fe){fe.printStackTrace();}catch(TransformException
te){te.printStackTrace();}
return transformedDP;
}// transformCoords
Thank you very much for your help already in advance,
Bernd.
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