Geo-api does not enter into it; it comes down to what version of
GeoTools you are using (2.4.2 perhaps?) and what version of the
epsg-xxxx.jar you are using (epsg-hsql is the most accurate but requires
a temp file, epsg-wkt is only suitable for applets etc...). It is also
really really common to confuse your axis order; getting them the wrong
way around is how I usually manage to get 100m out :-)
Cheers,
Jody
> Can anybody help with this? I have latitude and longitude(34.7473139,
> 45.0638444) for a shot point. When I used WGS84 to generate segp file I
> got about 98 meters difference for "Easting" value comparing with the
> original segp file. The following is the fragment of the codes. All
> classes I used are from geoapi-nogenerics-2.1-M2.jar. Did I use the
> wrong classes? Thanks very much.
>
> CRSAuthorityFactory crsFactory =
> FactoryFinder.getCRSAuthorityFactory("EPSG", null);
> CoordinateReferenceSystem crs =
> crsFactory.createCoordinateReferenceSystem("WGS 84 / UTM zone 38N");
> CoordinateReferenceSystem crsNad27 =
> crsFactory.createCoordinateReferenceSystem("NAD27");
> DirectPosition pt1 = new GeneralDirectPosition(34.7473139, 45.0638444);
> ((GeneralDirectPosition)pt1).setCoordinateReferenceSystem(crsNad27);
> GeotoolsCoordinateConverter converter = new
> GeotoolsCoordinateConverter(); --- my class implementing
> CoordinateConverter
> DirectPosition pt2 = converter.convert(pt1, crs);
> System.out.println(pt2); -------------------- The result I got is
> (505,942.407 3,844,897.644); but the value from original segp file is
> (505,843.7 3,845,023.5), almost 100 meters difference. This
> difference is very big.
>
> public class GeotoolsCoordinateConverter implements CoordinateConverter
> {
> protected CoordinateOperationFactory coFactory;
>
> public GeotoolsCoordinateConverter()
> {
> coFactory = FactoryFinder.getCoordinateOperationFactory(null);
> }
>
> public DirectPosition convert(DirectPosition pt,
> CoordinateReferenceSystem toCrs)
> {
> CoordinateOperation transform = null;
>
> try
> {
> transform =
> coFactory.createOperation(pt.getCoordinateReferenceSystem(), toCrs);
> }
> catch (OperationNotFoundException e)
> { e.printStackTrace(); }
> catch (FactoryException e)
> { e.printStackTrace(); }
>
> MathTransform trans = transform.getMathTransform();
> DirectPosition pt2 = null;
>
> try
> { pt2 = trans.transform(pt, null); }
> catch (MismatchedDimensionException e)
> { e.printStackTrace(); }
> catch (TransformException e)
> { e.printStackTrace(); }
> return pt2;
> }
> }
>
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