//License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.data.projection.proj;
import static java.lang.Math.PI;
import static java.lang.Math.abs;
import static java.lang.Math.asin;
import static java.lang.Math.atan;
import static java.lang.Math.atan2;
import static java.lang.Math.cos;
import static java.lang.Math.exp;
import static java.lang.Math.log;
import static java.lang.Math.pow;
import static java.lang.Math.sin;
import static java.lang.Math.sqrt;
import static java.lang.Math.tan;
import static java.lang.Math.toRadians;
import static org.openstreetmap.josm.tools.I18n.tr;
import org.openstreetmap.josm.data.projection.Ellipsoid;
import org.openstreetmap.josm.data.projection.ProjectionConfigurationException;
/**
* Projection for the SwissGrid CH1903 / L03, see <a href="https://en.wikipedia.org/wiki/Swiss_coordinate_system">Wikipedia article</a>.<br>
*
* Calculations were originally based on <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.12749.DownloadFile.tmp/ch1903wgs84en.pdf">
* simple formula</a>.<br>
*
* August 2010 update to <a href="http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.97912.DownloadFile.tmp/swissprojectionen.pdf">
* this formula (rigorous formulas)</a>.
*/
public class SwissObliqueMercator implements Proj {
private Ellipsoid ellps;
private double kR;
private double alpha;
private double b0;
private double K;
private static final double EPSILON = 1e-11;
@Override
public void initialize(ProjParameters params) throws ProjectionConfigurationException {
if (params.lat_0 == null)
throw new ProjectionConfigurationException(tr("Parameter ''{0}'' required.", "lat_0"));
ellps = params.ellps;
initialize(params.lat_0);
}
private void initialize(double lat_0) {
double phi0 = toRadians(lat_0);
kR = sqrt(1 - ellps.e2) / (1 - (ellps.e2 * pow(sin(phi0), 2)));
alpha = sqrt(1 + (ellps.eb2 * pow(cos(phi0), 4)));
b0 = asin(sin(phi0) / alpha);
K = log(tan(PI / 4 + b0 / 2)) - alpha
* log(tan(PI / 4 + phi0 / 2)) + alpha * ellps.e / 2
* log((1 + ellps.e * sin(phi0)) / (1 - ellps.e * sin(phi0)));
}
@Override
public String getName() {
return tr("Swiss Oblique Mercator");
}
@Override
public String getProj4Id() {
return "somerc";
}
@Override
public double[] project(double phi, double lambda) {
double S = alpha * log(tan(PI / 4 + phi / 2)) - alpha * ellps.e / 2
* log((1 + ellps.e * sin(phi)) / (1 - ellps.e * sin(phi))) + K;
double b = 2 * (atan(exp(S)) - PI / 4);
double l = alpha * lambda;
double lb = atan2(sin(l), sin(b0) * tan(b) + cos(b0) * cos(l));
double bb = asin(cos(b0) * sin(b) - sin(b0) * cos(b) * cos(l));
double y = kR * lb;
double x = kR / 2 * log((1 + sin(bb)) / (1 - sin(bb)));
return new double[] { y, x };
}
@Override
public double[] invproject(double y, double x) {
double lb = y / kR;
double bb = 2 * (atan(exp(x / kR)) - PI / 4);
double b = asin(cos(b0) * sin(bb) + sin(b0) * cos(bb) * cos(lb));
double l = atan2(sin(lb), cos(b0) * cos(lb) - sin(b0) * tan(bb));
double lambda = l / alpha;
double phi = b;
double S = 0;
double prevPhi = -1000;
int iteration = 0;
// iteration to finds S and phi
while (abs(phi - prevPhi) > EPSILON) {
if (++iteration > 30)
throw new RuntimeException("Two many iterations");
prevPhi = phi;
S = 1 / alpha * (log(tan(PI / 4 + b / 2)) - K) + ellps.e
* log(tan(PI / 4 + asin(ellps.e * sin(phi)) / 2));
phi = 2 * atan(exp(S)) - PI / 2;
}
return new double[] { phi, lambda };
}
}