Re: [Geotools-gt2-users] Accuracy of screen to world position transformations

[abel <apr...@in...>]

Hi, i comment my solution for display the coordinate when mouse move.

i use the following:

CoordinateOperationFactory coFactory =
FactoryFinder.getCoordinateOperationFactory(null);
MathTransform trans = null;
CoordinateFilter transFilter = null;
CoordinateReferenceSystem crsCoordenada = DefaultGeographicCRS.WGS84;

MathTransformFactory mtFactory =
FactoryFinder.getMathTransformFactory(null);

trans = mtFactory.createParameterizedTransform(parameters);

when mouse move calculate the coordinate:

ReferencedEnvelope referencedEnvelope = getContext().getAreaOfInterest();
        	double width = referencedEnvelope.getWidth();
            double height = referencedEnvelope.getHeight();
            double width2 = referencedEnvelope.getWidth() / 2.0;
            double height2 = referencedEnvelope.getHeight() / 2.0;
            
            double mapX = ((x * width) / (double) bounds.getWidth()) +
referencedEnvelope.getMinX();
            double mapY = (((bounds.getHeight() - y) * height) / (double) 
bounds.getHeight())
                    + referencedEnvelope.getMinY();

then apply the transform:

CoordinateOperation co =
coFactory.createOperation(referencedEnvelope.getCoordinateReferenceSystem(),
crsCoordenada);
            	transFilter = new
TransformationCoordinateFilter(co.getMathTransform());
Coordinate coor = new Coordinate(mapX, mapY);
            Point pointCoor = geomFac.createPoint(coor);
            pointCoor.apply(transFilter);




LepiMarbois wrote:
> 
> Dear All,
> I would like to get the position in lat/long (WGS84 ) of a point from a 
> map displayed in various projections (WGS84, Lambert, Mercator ).
> I am getting strange results with the code below.
> With a map of France displayed entirely on the screen I am getting 
> errors from nearly 0.5 degree, while if I zoom I am getting errors of 
> few minutes .
> That even if I modify the lenient parameter or sampling envelope points 
> in :
> ReferencedEnvelope worldwg84 = env.transform( 
> Projections.getCRS(Projections.WGS84), true,20);
> Is the code I am using wrong, is there a solution to get a better 
> accuracy ?
> Best regards,
> Pierre
> 
> Version used Geotools 2.4.4
> 
> CRS build with the following data :
> WGS84 = "GEOGCS[\"WGS84\", DATUM[\"WGS84\", SPHEROID[\"WGS84\", 
> 6378137.0, 298.257223563]], PRIMEM[\"Greenwich\", 0.0], 
> UNIT[\"degree\",0.017453292519943295], AXIS[\"Longitude\",EAST], 
> AXIS[\"Latitude\",NORTH]]";
> 
> LambertFrance = 
> "PROJCS[\"France_II\",GEOGCS[\"GCS_NTF_Paris\",DATUM[\"Nouvelle_Triangulation_Francaise\",SPHEROID[\"Clarke_1880_IGN\",6378249.2,293.46602]],PRIMEM[\"Paris\",2.337229166666667],UNIT[\"degree\",0.0174532925199433]],PROJECTION[\"Lambert_Conformal_Conic_2SP\"],PARAMETER[\"False_Easting\",600000],PARAMETER[\"False_Northing\",2200000],PARAMETER[\"Central_Meridian\",0],PARAMETER[\"Standard_Parallel_1\",45.898918964419],PARAMETER[\"Standard_Parallel_2\",47.696014502038],PARAMETER[\"Latitude_Of_Origin\",46.8],UNIT[\"Meter\",1]]"; 
> 
> 
> Mercator = "PROJCS[\"WGS84+GRS80 / Mercator\",GEOGCS[\"WGS 
> 84\",DATUM[\"WGS_1984\",SPHEROID[\"GRS 
> 1980\",6378137,298.257222101],TOWGS84[0,0,0]],PRIMEM[\"Greenwich\",0],UNIT[\"Decimal_Degree\",0.0174532925199433]],PROJECTION[\"Mercator_1SP\"],PARAMETER[\"central_meridian\",0],UNIT[\"Meter\",1]]"; 
> 
> 
> 
> public void mouseMoved(MouseEvent e) {
> try
> {Point2D pntécran = (Point2D) e.getPoint();
> ReferencedEnvelope env = m_context.getAreaOfInterest();
> ReferencedEnvelope worldwg84 = env.transform( 
> Projections.getCRS(Projections.WGS84), true,20);
> // true: lenient parameter
> AffineTransform world2screen = RendererUtilities.worldToScreenTransform(
> worldwg84, m_mapPane.getBounds(),Projections.getCRS(Projections.WGS84));
> AffineTransform screen2world2 = world2screen.createInverse();
> Point2D res = screen2world2.transform(pntécran,null);
> m_statusBar.setMessage(Util.to_Latitude(res.getY())+ " , " + 
> Util.to_Longitude(res.getX()));
> }
> catch (NoninvertibleTransformException ex)
> {System.out.println ("erreur transformlecture feature source " +ex);
> }
> …..
> 
> 
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