1 | //License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.data.projection.proj;
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3 |
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4 | import static java.lang.Math.*;
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5 |
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6 | import static org.openstreetmap.josm.tools.I18n.tr;
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7 |
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8 | import org.openstreetmap.josm.data.projection.Ellipsoid;
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9 |
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10 | /**
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11 | * Projection for the SwissGrid CH1903 / L03, see http://de.wikipedia.org/wiki/Swiss_Grid.
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12 | *
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13 | * Calculations are based on formula from
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14 | * http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.12749.DownloadFile.tmp/ch1903wgs84en.pdf
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15 | *
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16 | * August 2010 update to this formula (rigorous formulas)
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17 | * http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/sys/refsys/switzerland.parsysrelated1.37696.downloadList.97912.DownloadFile.tmp/swissprojectionen.pdf
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18 | */
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19 | public class SwissObliqueMercator implements Proj {
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20 |
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21 | private final Ellipsoid ellps;
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22 | private double kR;
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23 | private double alpha;
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24 | private double b0;
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25 | private double K;
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26 |
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27 | private static final double EPSILON = 1e-11;
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28 |
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29 | public SwissObliqueMercator(Ellipsoid ellps, double lat_0) {
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30 | this.ellps = ellps;
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31 | updateParameters(lat_0);
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32 | }
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33 |
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34 | public void updateParameters(double lat_0) {
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35 | double phi0 = toRadians(lat_0);
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36 | kR = sqrt(1 - ellps.e2) / (1 - (ellps.e2 * pow(sin(phi0), 2)));
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37 | alpha = sqrt(1 + (ellps.eb2 * pow(cos(phi0), 4)));
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38 | b0 = asin(sin(phi0) / alpha);
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39 | K = log(tan(PI / 4 + b0 / 2)) - alpha
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40 | * log(tan(PI / 4 + phi0 / 2)) + alpha * ellps.e / 2
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41 | * log((1 + ellps.e * sin(phi0)) / (1 - ellps.e * sin(phi0)));
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42 | }
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43 |
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44 | @Override
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45 | public String getName() {
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46 | return tr("Swiss Oblique Mercator");
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47 | }
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48 |
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49 | @Override
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50 | public String getProj4Id() {
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51 | return "somerc";
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52 | }
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53 |
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54 | @Override
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55 | public double[] project(double phi, double lambda) {
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56 |
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57 | double S = alpha * log(tan(PI / 4 + phi / 2)) - alpha * ellps.e / 2
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58 | * log((1 + ellps.e * sin(phi)) / (1 - ellps.e * sin(phi))) + K;
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59 | double b = 2 * (atan(exp(S)) - PI / 4);
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60 | double l = alpha * lambda;
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61 |
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62 | double lb = atan2(sin(l), sin(b0) * tan(b) + cos(b0) * cos(l));
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63 | double bb = asin(cos(b0) * sin(b) - sin(b0) * cos(b) * cos(l));
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64 |
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65 | double y = kR * lb;
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66 | double x = kR / 2 * log((1 + sin(bb)) / (1 - sin(bb)));
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67 |
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68 | return new double[] { y, x };
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69 | }
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70 |
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71 | @Override
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72 | public double[] invproject(double y, double x) {
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73 | double lb = y / kR;
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74 | double bb = 2 * (atan(exp(x / kR)) - PI / 4);
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75 |
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76 | double b = asin(cos(b0) * sin(bb) + sin(b0) * cos(bb) * cos(lb));
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77 | double l = atan2(sin(lb), cos(b0) * cos(lb) - sin(b0) * tan(bb));
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78 |
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79 | double lambda = l / alpha;
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80 | double phi = b;
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81 | double S = 0;
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82 |
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83 | double prevPhi = -1000;
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84 | int iteration = 0;
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85 | // iteration to finds S and phi
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86 | while (abs(phi - prevPhi) > EPSILON) {
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87 | if (++iteration > 30)
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88 | throw new RuntimeException("Two many iterations");
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89 | prevPhi = phi;
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90 | S = 1 / alpha * (log(tan(PI / 4 + b / 2)) - K) + ellps.e
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91 | * log(tan(PI / 4 + asin(ellps.e * sin(phi)) / 2));
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92 | phi = 2 * atan(exp(S)) - PI / 2;
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93 | }
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94 | return new double[] { phi, lambda };
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95 | }
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96 |
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97 | }
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