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 org.openstreetmap.josm.tools.I18n.tr;
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5 |
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6 | import org.openstreetmap.josm.data.Bounds;
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7 | import org.openstreetmap.josm.data.projection.ProjectionConfigurationException;
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8 |
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9 | /**
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10 | * Cassini-Soldner Projection (EPSG code 9806).
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11 | * The Cassini-Soldner Projection is the ellipsoidal version of the Cassini
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12 | * projection for the sphere. It is not conformal but as it is relatively simple
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13 | * to construct it was extensively used in the last century and is still useful
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14 | * for mapping areas with limited longitudinal extent. It has now largely
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15 | * been replaced by the conformal Transverse Mercator which it resembles. Like this,
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16 | * it has a straight central meridian along which the scale is true, all other
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17 | * meridians and parallels are curved, and the scale distortion increases
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18 | * rapidly with increasing distance from the central meridian.
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19 | * <p>
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20 | *
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21 | * This class has been derived from the implementation of the Geotools project;
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22 | * git 8cbf52d, org.geotools.referencing.operation.projection.CassiniSoldner
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23 | * at the time of migration.
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24 | */
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25 | public class CassiniSoldner extends AbstractProj {
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26 |
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27 | /**
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28 | * Meridian distance at the {@code latitudeOfOrigin}.
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29 | * Used for calculations for the ellipsoid.
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30 | */
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31 | private double ml0;
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32 |
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33 | /**
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34 | * Contants used for the forward and inverse transform for the eliptical
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35 | * case of the Cassini-Soldner.
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36 | */
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37 | private static final double C1 = 0.16666666666666666666;
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38 | private static final double C2 = 0.008333333333333333333;
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39 | private static final double C3 = 0.041666666666666666666;
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40 | private static final double C4 = 0.33333333333333333333;
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41 | private static final double C5 = 0.066666666666666666666;
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42 |
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43 | @Override
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44 | public String getName() {
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45 | return tr("Cassini-Soldner");
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46 | }
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47 |
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48 | @Override
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49 | public String getProj4Id() {
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50 | return "cass";
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51 | }
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52 |
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53 | @Override
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54 | public void initialize(ProjParameters params) throws ProjectionConfigurationException {
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55 | super.initialize(params);
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56 | if (params.lat0 == null)
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57 | throw new ProjectionConfigurationException(tr("Parameter ''{0}'' required.", "lat_0"));
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58 | double latitudeOfOrigin = Math.toRadians(params.lat0);
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59 | ml0 = mlfn(latitudeOfOrigin, Math.sin(latitudeOfOrigin), Math.cos(latitudeOfOrigin));
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60 | }
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61 |
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62 | @Override
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63 | public double[] project(double phi, double lam) {
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64 | double sinphi = Math.sin(phi);
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65 | double cosphi = Math.cos(phi);
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66 |
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67 | double n = 1.0 / (Math.sqrt(1.0 - e2 * sinphi * sinphi));
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68 | double tn = Math.tan(phi);
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69 | double t = tn * tn;
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70 | double a1 = lam * cosphi;
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71 | double c = cosphi * cosphi * e2 / (1 - e2);
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72 | double a2 = a1 * a1;
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73 |
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74 | double x = n * a1 * (1.0 - a2 * t * (C1 - (8.0 - t + 8.0 * c) * a2 * C2));
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75 | double y = mlfn(phi, sinphi, cosphi) - ml0 + n * tn * a2 * (0.5 + (5.0 - t + 6.0 * c) * a2 * C3);
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76 | return new double[] {x, y};
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77 | }
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78 |
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79 | @Override
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80 | public double[] invproject(double x, double y) {
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81 | double ph1 = inv_mlfn(ml0 + y);
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82 | double tn = Math.tan(ph1);
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83 | double t = tn * tn;
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84 | double n = Math.sin(ph1);
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85 | double r = 1.0 / (1.0 - e2 * n * n);
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86 | n = Math.sqrt(r);
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87 | r *= (1.0 - e2) * n;
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88 | double dd = x / n;
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89 | double d2 = dd * dd;
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90 | double phi = ph1 - (n * tn / r) * d2 * (0.5 - (1.0 + 3.0 * t) * d2 * C3);
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91 | double lam = dd * (1.0 + t * d2 * (-C4 + (1.0 + 3.0 * t) * d2 * C5)) / Math.cos(ph1);
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92 | return new double[] {phi, lam};
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93 | }
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94 |
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95 | @Override
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96 | public Bounds getAlgorithmBounds() {
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97 | return new Bounds(-89, -1.0, 89, 1.0, false);
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98 | }
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99 | }
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