/*
* SphericalPolarCoordinates.java
*
* Copyright (c) 2002-2015 Alexei Drummond, Andrew Rambaut and Marc Suchard
*
* This file is part of BEAST.
* See the NOTICE file distributed with this work for additional
* information regarding copyright ownership and licensing.
*
* BEAST is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* BEAST is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with BEAST; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
package dr.geo.math;
import dr.evolution.continuous.Contrastable;
public class SphericalPolarCoordinates implements Contrastable {
/**
* Create spherical polar coordinates from the given vector
*/
public SphericalPolarCoordinates(Vector3D v) {
this(v, v.modulus());
}
/**
* Create spherical polar coordinates from the given vector
*/
public SphericalPolarCoordinates(Vector3D v, double newRadius) {
radius = v.modulus();
theta = Math.acos(v.getZ()/radius);
phi = Math.atan(v.getY()/v.getX());
if (v.getY() < 0) phi += Math.PI;
radius = newRadius;
}
/**
* Create spherical polar coordinates from given latitude and longitude
*/
public SphericalPolarCoordinates(double latitude, double longitude) {
this(latitude,longitude,VOLUMETRIC_RADIUS_OF_EARTH);
}
public SphericalPolarCoordinates(double latitude, double longitude, double radius) {
this.radius = radius;
theta = (90.0-latitude)*Math.PI/180.0;
if (longitude < 0) longitude += 360;
phi = longitude * Math.PI/180;
}
public Vector3D getCartesianCoordinates() {
double x = radius * Math.sin(theta) * Math.cos(phi);
double y = radius * Math.sin(theta) * Math.sin(phi);
double z = radius * Math.cos(theta);
return new Vector3D(x, y, z);
}
/**
* @return the latitude of these spherical polar coordinates in degrees.
*/
public double getLatitude() {
return 90 - (theta * 180.0 / Math.PI);
}
/**
* @return the longitude of these spherical polar coordinates in degrees.
*/
public double getLongitude() {
double degrees = phi * 180.0 / Math.PI;
if (degrees > 180.0) {
degrees -= 360;
}
return degrees;
}
/**
* @return the angle (along the great circle) between this position and the given position.
*/
public double angle(SphericalPolarCoordinates B) {
Vector3D v1 = getCartesianCoordinates().normalized();
Vector3D v2 = B.getCartesianCoordinates().normalized();
double sinAngle = v1.cross(v2).modulus();
double cosAngle = v1.dot(v2);
double angle = Math.atan2(sinAngle, cosAngle);
return angle;
}
/**
* @return the great circle distance between this position and the given position.
*/
public double distance(SphericalPolarCoordinates B) {
return angle(B) * radius;
}
/**
* @return the mid point of the two positions.
*/
public static SphericalPolarCoordinates getMidpoint(SphericalPolarCoordinates A, SphericalPolarCoordinates B) {
return interpolate(A, B, 0.5);
}
/**
* alpha = 0 implies returning A, alpha = 1 implies returning B
* @return a point between the two positions.
*/
public static SphericalPolarCoordinates interpolate(SphericalPolarCoordinates A, SphericalPolarCoordinates B, double alpha) {
Vector3D from = A.getCartesianCoordinates().normalized();
Vector3D to = B.getCartesianCoordinates().normalized();
double cosang = from.dot(to);
if (cosang < 0) {
cosang = -cosang;
to.negate();
System.out.println("Argg");
}
double fracFrom, fracTo;
if (cosang > (0.999995) ) { // small angle limit
fracFrom = alpha;
fracTo = 1.0-alpha;
} else { // normal case
double ang = Math.acos( cosang );
fracFrom = Math.sin( alpha * ang);
fracTo = Math.sin( (1.0-alpha) * ang );
}
Vector3D inbetween = from.mul(fracFrom).add(to.mul(fracTo)).normalized();
return new SphericalPolarCoordinates(inbetween, A.getRadius());
}
public double getRadius() { return radius; }
public String toString() {
return toLatLongString();
//return "polarCoordinates[theta="+theta+", phi=" + phi + ", r=" + radius + "]";
}
public String toLatLongString() {
double lat1 = getLatitude();
double long1 = getLongitude();
String latSuffix = " N";
if (lat1 < 0) {
lat1 = -lat1;
latSuffix = " S";
}
String longSuffix = " E";
if (long1 < 0) {
long1 = -long1;
longSuffix = " W";
}
return lat1 + latSuffix + ", " + long1 + longSuffix;
}
public static void main(String[] args) {
double latitude1 = 66.0;
double longitude1 = -174.0;
double latitude2 = 64.0;
double longitude2 = -142.0;
SphericalPolarCoordinates p1 = new SphericalPolarCoordinates(latitude1, longitude1);
SphericalPolarCoordinates p2 = new SphericalPolarCoordinates(latitude2, longitude2);
SphericalPolarCoordinates p1a = new SphericalPolarCoordinates(p1.getCartesianCoordinates());
SphericalPolarCoordinates p2a = new SphericalPolarCoordinates(p2.getCartesianCoordinates());
System.out.println("point1="+p1.toLatLongString());
System.out.println("point2="+p2.toLatLongString());
System.out.println("point1_test="+p1a.toLatLongString());
System.out.println("point2_test="+p2a.toLatLongString());
System.out.println("distance=" + p1.distance(p2) + " kilometres");
System.out.println("midpoint=" + getMidpoint(p1, p2).toLatLongString());
}
//************************************************************************
// Contrastable interface
//************************************************************************
public double getDifference(Contrastable spc) {
if (spc instanceof SphericalPolarCoordinates) {
return distance((SphericalPolarCoordinates)spc);
} else throw new IllegalArgumentException("Expected a spherical polar coordinate");
}
public Contrastable getWeightedMean(double weight1, Contrastable spc1, double weight2, Contrastable spc2) {
double alpha = weight1 / (weight1 + weight2);
if (spc1 instanceof SphericalPolarCoordinates && spc2 instanceof SphericalPolarCoordinates) {
return interpolate((SphericalPolarCoordinates)spc1, (SphericalPolarCoordinates)spc2, alpha);
} else throw new IllegalArgumentException("Expected a spherical polar coordinate");
}
//************************************************************************
// Private members
//************************************************************************
// angle off of north pole (0 to pi)
private double theta = 0.0;
// angle east of greenwich (0 to 2*pi)
private double phi = 0.0;
// radius
private double radius = 1.0;
private static double VOLUMETRIC_RADIUS_OF_EARTH = 6371.0;
}