Examples with ContextualParameters org.apache.sis.referencing.operation.transform.ContextualParameters used on opensource projects

Example 1 with ContextualParameters

use of org.apache.sis.referencing.operation.transform.ContextualParameters in project sis by apache.

the class Equirectangular method createMathTransform.

/**
 * Creates an Equirectangular projection from the specified group of parameter values. This method is an
 * adaptation of {@link org.apache.sis.referencing.operation.projection.NormalizedProjection} constructor,
 * reproduced in this method because we will create an affine transform instead than the usual projection
 * classes.
 *
 * @param  factory     the factory to use if this constructor needs to create other math transforms.
 * @param  parameters  the parameter values that define the transform to create.
 * @return the map projection created from the given parameter values.
 * @throws FactoryException if an error occurred while creating the math transform.
 */
@Override
public MathTransform createMathTransform(final MathTransformFactory factory, final ParameterValueGroup parameters) throws FactoryException {
    final Parameters p = Parameters.castOrWrap(parameters);
    final ContextualParameters context = new ContextualParameters(this);
    double a = getAndStore(p, context, MapProjection.SEMI_MAJOR);
    double b = getAndStore(p, context, MapProjection.SEMI_MINOR);
    double λ0 = getAndStore(p, context, LONGITUDE_OF_ORIGIN);
    double φ0 = getAndStore(p, context, LATITUDE_OF_ORIGIN);
    double φ1 = getAndStore(p, context, STANDARD_PARALLEL);
    double fe = getAndStore(p, context, FALSE_EASTING);
    double fn = getAndStore(p, context, FALSE_NORTHING);
    /*
         * Perform following transformation, in that order. Note that following
         * AffineTransform convention, the Java code appears in reverse order:
         *
         *   1) Subtract φ0 to the latitude.
         *   2) Subtract λ0 to the longitude.
         *   3) Convert degrees to radians.
         *   4) Scale longitude by cos(φ1).
         */
    φ1 = toRadians(φ1);
    final MatrixSIS normalize = context.getMatrix(ContextualParameters.MatrixRole.NORMALIZATION);
    normalize.convertBefore(0, cos(φ1), null);
    context.normalizeGeographicInputs(λ0).convertBefore(1, null, -φ0);
    /*
         * At this point, we usually invoke 'denormalize.convertAfter(…, a, …)' where 'a' (the semi-major axis length)
         * is taken as the Earth radius (R). However quoting EPSG: "If the figure of the earth used is an ellipsoid
         * rather than a sphere then R should be calculated as the radius of the conformal sphere at the projection
         * origin at latitude φ1 using the formula for RC given in section 1.2, table 3".
         */
    if (a != b) {
        final double rs = b / a;
        final double sinφ1 = sin(φ1);
        a = b / (1 - (1 - rs * rs) * (sinφ1 * sinφ1));
    }
    final DoubleDouble k = new DoubleDouble(a);
    final MatrixSIS denormalize = context.getMatrix(ContextualParameters.MatrixRole.DENORMALIZATION);
    denormalize.convertAfter(0, k, new DoubleDouble(fe));
    denormalize.convertAfter(1, k, new DoubleDouble(fn));
    /*
         * Creates the ConcatenatedTransform, letting the factory returns the cached instance
         * if the caller already invoked this method previously (which usually do not happen).
         */
    MathTransform mt = context.completeTransform(factory, MathTransforms.identity(2));
    if (mt instanceof AffineTransform) {
        // Always true in Apache SIS implementation.
        mt = new ParameterizedAffine((AffineTransform) mt, context, true);
    }
    return mt;
}