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package uk.ac.rdg.resc.edal.grid;

import org.opengis.referencing.crs.CoordinateReferenceSystem;
import uk.ac.rdg.resc.edal.util.GISUtils;

/**
 * This is an abstract implementation of a {@link HorizontalGrid} for which
 * there exists a transformation to convert WGS84 to the native CRS.
 *
 * This transformation is invisible externally - i.e.
 * {@link AbstractTransformedGrid#getCoordinateReferenceSystem()} will return
 * {@link DefaultGeographicCRS#WGS84} and all operations behave as though this
 * is the co-ordinate reference system. However, this class also exposes the
 * method
 * {@link AbstractTransformedGrid#transformNativeHeadingToWgs84(double, double, double, double)}
 * so that vector transforms can be handled.
 */
public abstract class AbstractTransformedGrid implements HorizontalGrid {
    private static final long serialVersionUID = 1L;

    /**
     * Transforms a heading in native grid co-ordinates (degrees clockwise from
     * positive y-direction) into a heading in WGS84 (degrees clockwise from
     * north).
     *
     * @param xComp
     *            The x-component of the heading
     * @param yComp
     *            The y-component of the heading
     * @param lon
     *            The longitude of the given components
     * @param lat
     *            The latitude of the given components
     * @return The transformed heading
     */
    public abstract double transformNativeHeadingToWgs84(double xComp, double yComp, double lon,
            double lat);

    /**
     * Always returns {@link DefaultGeographicCRS#WGS84}. Transformations
     * between native CRS and WGS84 are done behind the scenes
     */
    @Override
    public final CoordinateReferenceSystem getCoordinateReferenceSystem() {
        return GISUtils.defaultGeographicCRS();
    }
}
