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.Bounds;
020import org.openstreetmap.josm.data.projection.Ellipsoid;
021import org.openstreetmap.josm.data.projection.ProjectionConfigurationException;
022
023// CHECKSTYLE.OFF: LineLength
024
025/**
026 * Projection for the SwissGrid CH1903 / L03, see <a href="https://en.wikipedia.org/wiki/Swiss_coordinate_system">Wikipedia article</a>.<br>
027 *
028 * Calculations were originally based on
029 * <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.12749.DownloadFile.tmp/ch1903wgs84en.pdf">
030 * simple formula</a>.<br>
031 *
032 * August 2010 update to
033 * <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.97912.DownloadFile.tmp/swissprojectionen.pdf">
034 * this formula (rigorous formulas)</a>.
035 */
036public class SwissObliqueMercator implements Proj {
037
038    // CHECKSTYLE.ON: LineLength
039
040    private Ellipsoid ellps;
041    private double kR;
042    private double alpha;
043    private double b0;
044    private double k;
045
046    private static final double EPSILON = 1e-11;
047
048    @Override
049    public void initialize(ProjParameters params) throws ProjectionConfigurationException {
050        if (params.lat0 == null)
051            throw new ProjectionConfigurationException(tr("Parameter ''{0}'' required.", "lat_0"));
052        ellps = params.ellps;
053        initialize(params.lat0);
054    }
055
056    private void initialize(double lat_0) {
057        double phi0 = toRadians(lat_0);
058        kR = sqrt(1 - ellps.e2) / (1 - (ellps.e2 * pow(sin(phi0), 2)));
059        alpha = sqrt(1 + (ellps.eb2 * pow(cos(phi0), 4)));
060        b0 = asin(sin(phi0) / alpha);
061        k = log(tan(PI / 4 + b0 / 2)) - alpha
062            * log(tan(PI / 4 + phi0 / 2)) + alpha * ellps.e / 2
063            * log((1 + ellps.e * sin(phi0)) / (1 - ellps.e * sin(phi0)));
064    }
065
066    @Override
067    public String getName() {
068        return tr("Swiss Oblique Mercator");
069    }
070
071    @Override
072    public String getProj4Id() {
073        return "somerc";
074    }
075
076    @Override
077    public double[] project(double phi, double lambda) {
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
118    @Override
119    public Bounds getAlgorithmBounds() {
120        return new Bounds(-85, -179, 85, 179, false);
121    }
122}