001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.data.projection.proj;
003
004import static java.lang.Math.PI;
005import static java.lang.Math.abs;
006import static java.lang.Math.asin;
007import static java.lang.Math.atan;
008import static java.lang.Math.atan2;
009import static java.lang.Math.cos;
010import static java.lang.Math.exp;
011import static java.lang.Math.log;
012import static java.lang.Math.pow;
013import static java.lang.Math.sin;
014import static java.lang.Math.sqrt;
015import static java.lang.Math.tan;
016import static java.lang.Math.toRadians;
017import static org.openstreetmap.josm.tools.I18n.tr;
018
019import org.openstreetmap.josm.data.projection.Ellipsoid;
020import org.openstreetmap.josm.data.projection.ProjectionConfigurationException;
021
022// CHECKSTYLE.OFF: LineLength
023
024/**
025 * Projection for the SwissGrid CH1903 / L03, see <a href="https://en.wikipedia.org/wiki/Swiss_coordinate_system">Wikipedia article</a>.<br>
026 *
027 * Calculations were originally based on
028 * <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.12749.DownloadFile.tmp/ch1903wgs84en.pdf">
029 * simple formula</a>.<br>
030 *
031 * August 2010 update to
032 * <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.97912.DownloadFile.tmp/swissprojectionen.pdf">
033 * this formula (rigorous formulas)</a>.
034 */
035public class SwissObliqueMercator implements Proj {
036
037    // CHECKSTYLE.ON: LineLength
038
039    private Ellipsoid ellps;
040    private double kR;
041    private double alpha;
042    private double b0;
043    private double k;
044
045    private static final double EPSILON = 1e-11;
046
047    @Override
048    public void initialize(ProjParameters params) throws ProjectionConfigurationException {
049        if (params.lat0 == null)
050            throw new ProjectionConfigurationException(tr("Parameter ''{0}'' required.", "lat_0"));
051        ellps = params.ellps;
052        initialize(params.lat0);
053    }
054
055    private void initialize(double lat_0) {
056        double phi0 = toRadians(lat_0);
057        kR = sqrt(1 - ellps.e2) / (1 - (ellps.e2 * pow(sin(phi0), 2)));
058        alpha = sqrt(1 + (ellps.eb2 * pow(cos(phi0), 4)));
059        b0 = asin(sin(phi0) / alpha);
060        k = log(tan(PI / 4 + b0 / 2)) - alpha
061            * log(tan(PI / 4 + phi0 / 2)) + alpha * ellps.e / 2
062            * log((1 + ellps.e * sin(phi0)) / (1 - ellps.e * sin(phi0)));
063    }
064
065    @Override
066    public String getName() {
067        return tr("Swiss Oblique Mercator");
068    }
069
070    @Override
071    public String getProj4Id() {
072        return "somerc";
073    }
074
075    @Override
076    public double[] project(double phi, double lambda) {
077
078        double S = alpha * log(tan(PI / 4 + phi / 2)) - alpha * ellps.e / 2
079            * log((1 + ellps.e * sin(phi)) / (1 - ellps.e * sin(phi))) + k;
080        double b = 2 * (atan(exp(S)) - PI / 4);
081        double l = alpha * lambda;
082
083        double lb = atan2(sin(l), sin(b0) * tan(b) + cos(b0) * cos(l));
084        double bb = asin(cos(b0) * sin(b) - sin(b0) * cos(b) * cos(l));
085
086        double y = kR * lb;
087        double x = kR / 2 * log((1 + sin(bb)) / (1 - sin(bb)));
088
089        return new double[] {y, x};
090    }
091
092    @Override
093    public double[] invproject(double y, double x) {
094        double lb = y / kR;
095        double bb = 2 * (atan(exp(x / kR)) - PI / 4);
096
097        double b = asin(cos(b0) * sin(bb) + sin(b0) * cos(bb) * cos(lb));
098        double l = atan2(sin(lb), cos(b0) * cos(lb) - sin(b0) * tan(bb));
099
100        double lambda = l / alpha;
101        double phi = b;
102        double s = 0;
103
104        double prevPhi = -1000;
105        int iteration = 0;
106        // iteration to finds S and phi
107        while (abs(phi - prevPhi) > EPSILON) {
108            if (++iteration > 30)
109                throw new RuntimeException("Two many iterations");
110            prevPhi = phi;
111            s = 1 / alpha * (log(tan(PI / 4 + b / 2)) - k) + ellps.e
112            * log(tan(PI / 4 + asin(ellps.e * sin(phi)) / 2));
113            phi = 2 * atan(exp(s)) - PI / 2;
114        }
115        return new double[] {phi, lambda};
116    }
117}