Java Doc for LocalizationGrid.java in  » GIS » GeoTools-2.4.1 » org » geotools » referencing » operation » builder » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The LocalizationGrid class is usefull when the " " transform for a coverage is not some kind of global mathematical relationship like an . Instead, the "real world" coordinates are explicitly specified for each pixels. If the real world coordinates are know only for some pixels at a fixed interval, then a transformation can be constructed by the concatenation of an affine transform with a grid of localization.

After a LocalizationGrid object has been fully constructed (i.e. real world coordinates have been specified for all grid cells), a transformation from grid coordinates to "real world" coordinates can be obtained with the LocalizationGrid.getMathTransform method. If this transformation is close enough to an affine transform, then an instance of AffineTransform is returned. Otherwise, a transform backed by the localization grid is returned.

The example below goes through the steps of constructing a coordinate reference system for a grid coverage from its grid of localization. This example assumes that the "real world" coordinates are longitudes and latitudes on the ellipsoid.

// // Constructs a localization grid of size 10×10. // LocalizationGrid grid = new LocalizationGrid(10,10); for (int j=0; j<10; j++) { for (int i=0; i<10; i++) { double x = ...; // Set longitude here double y = ...; // Set latitude here grid. (i,j,x,y); } } // // Constructs the grid coordinate reference system. degree is the polynomial // degree (e.g. 2) for a math transform that approximately map the grid of localization. // For a more accurate (but not always better) math transform backed by the whole grid, // invokes instead, or use the special value of 0 for the degree // argument. // MathTransform2D realToGrid = grid. (degree).inverse(); CoordinateReferenceSystem realCRS = DefaultGeographicCRS.WGS84; CoordinateReferenceSystem gridCRS = new ("The grid CRS", new (realToGrid), realCRS, // The target ("real world") CRS realToGrid, // How the grid CRS relates to the "real world" CRS ); // // Constructs the grid coverage using the grid coordinate system (not the "real world" // one). It is usefull to display the coverage in its native CRS before we resample it. // Note that if the grid of localization does not define the geographic location for // all pixels, then we need to specify some affine transform in place of the call to // IdentityTransform. For example if the grid of localization defines the location of // 1 pixel, then skip 3, then defines the location of 1 pixel, etc., then the affine // transform should be AffineTransform.getScaleInstance(0.25, 0.25). // raster = .createBandedRaster(DataBuffer.TYPE_FLOAT, width, height, 1, null); for (int y=0; ysome_value); } } GridCoverageFactory factory = FactoryFinder.getGridCoverageFactory(null); GridCoverage coverage = factory.create("My grayscale coverage", raster, gridCRS, IdentityTransform.create(2), null, null, null, null, null); coverage.show(); // // Projects the coverage from its current 'gridCS' to the 'realCS'. If the grid of // localization was built from the orbit of some satellite, then the projected // coverage will tpypically have a curved aspect. // coverage = (Coverage2D) Operations.DEFAULT.resample(coverage, realCRS); coverage.show();

• Coordinates in a row must be increasing or decreasing.

• Coordinates in a row must be increasing or decreasing. If strict is true , then coordinates must be strictly increasing or decreasing (i.e. equals value are not accepted). NaN values are always ignored.
• Coordinates in all rows must be increasing, or coordinates in all rows must be decreasing.
• Idem for columns (Coordinates in a columns must be increasing or decreasing, etc.).