001// License: GPL. For details, see LICENSE file. 002package org.openstreetmap.josm.data.projection.proj; 003 004import static org.openstreetmap.josm.tools.I18n.tr; 005 006import org.openstreetmap.josm.data.Bounds; 007import org.openstreetmap.josm.data.projection.ProjectionConfigurationException; 008import org.openstreetmap.josm.tools.Utils; 009 010/** 011 * Cassini-Soldner Projection (EPSG code 9806). 012 * The Cassini-Soldner Projection is the ellipsoidal version of the Cassini 013 * projection for the sphere. It is not conformal but as it is relatively simple 014 * to construct it was extensively used in the last century and is still useful 015 * for mapping areas with limited longitudinal extent. It has now largely 016 * been replaced by the conformal Transverse Mercator which it resembles. Like this, 017 * it has a straight central meridian along which the scale is true, all other 018 * meridians and parallels are curved, and the scale distortion increases 019 * rapidly with increasing distance from the central meridian. 020 * <p> 021 * 022 * This class has been derived from the implementation of the Geotools project; 023 * git 8cbf52d, org.geotools.referencing.operation.projection.CassiniSoldner 024 * at the time of migration. 025 */ 026public class CassiniSoldner extends AbstractProj { 027 028 /** 029 * Meridian distance at the {@code latitudeOfOrigin}. 030 * Used for calculations for the ellipsoid. 031 */ 032 private double ml0; 033 034 /** 035 * Contants used for the forward and inverse transform for the eliptical 036 * case of the Cassini-Soldner. 037 */ 038 private static final double C1 = 0.16666666666666666666; 039 private static final double C2 = 0.008333333333333333333; 040 private static final double C3 = 0.041666666666666666666; 041 private static final double C4 = 0.33333333333333333333; 042 private static final double C5 = 0.066666666666666666666; 043 044 @Override 045 public String getName() { 046 return tr("Cassini-Soldner"); 047 } 048 049 @Override 050 public String getProj4Id() { 051 return "cass"; 052 } 053 054 @Override 055 public void initialize(ProjParameters params) throws ProjectionConfigurationException { 056 super.initialize(params); 057 if (params.lat0 == null) 058 throw new ProjectionConfigurationException(tr("Parameter ''{0}'' required.", "lat_0")); 059 double latitudeOfOrigin = Utils.toRadians(params.lat0); 060 ml0 = mlfn(latitudeOfOrigin, Math.sin(latitudeOfOrigin), Math.cos(latitudeOfOrigin)); 061 } 062 063 @Override 064 public double[] project(double phi, double lam) { 065 double sinphi = Math.sin(phi); 066 double cosphi = Math.cos(phi); 067 068 double n = 1.0 / (Math.sqrt(1.0 - e2 * sinphi * sinphi)); 069 double tn = Math.tan(phi); 070 double t = tn * tn; 071 double a1 = lam * cosphi; 072 double c = cosphi * cosphi * e2 / (1 - e2); 073 double a2 = a1 * a1; 074 075 double x = n * a1 * (1.0 - a2 * t * (C1 - (8.0 - t + 8.0 * c) * a2 * C2)); 076 double y = mlfn(phi, sinphi, cosphi) - ml0 + n * tn * a2 * (0.5 + (5.0 - t + 6.0 * c) * a2 * C3); 077 return new double[] {x, y}; 078 } 079 080 @Override 081 public double[] invproject(double x, double y) { 082 double ph1 = invMlfn(ml0 + y); 083 double tn = Math.tan(ph1); 084 double t = tn * tn; 085 double n = Math.sin(ph1); 086 double r = 1.0 / (1.0 - e2 * n * n); 087 n = Math.sqrt(r); 088 r *= (1.0 - e2) * n; 089 double dd = x / n; 090 double d2 = dd * dd; 091 double phi = ph1 - (n * tn / r) * d2 * (0.5 - (1.0 + 3.0 * t) * d2 * C3); 092 double lam = dd * (1.0 + t * d2 * (-C4 + (1.0 + 3.0 * t) * d2 * C5)) / Math.cos(ph1); 093 return new double[] {phi, lam}; 094 } 095 096 @Override 097 public Bounds getAlgorithmBounds() { 098 return new Bounds(-89, -1.0, 89, 1.0, false); 099 } 100}