source: josm/trunk/src/org/openstreetmap/josm/data/coor/LatLon.java@ 608

// License: GPL. Copyright 2007 by Immanuel Scholz and others
package org.openstreetmap.josm.data.coor;

import org.openstreetmap.josm.data.Bounds;
import org.openstreetmap.josm.data.projection.Projection;
import java.text.NumberFormat;

/**
 * LatLon are unprojected latitude / longitude coordinates.
 * 
 * This class is immutable.
 * 
 * @author Imi
 */
public class LatLon extends Coordinate {

        public LatLon(double lat, double lon) {
                super(lon, lat);
        }

        public double lat() {
                return y;
        }

        public double lon() {
                return x;
        }

        /**
         * @return <code>true</code>, if the other point has almost the same lat/lon
         * values, only differ by no more than 1/Projection.MAX_SERVER_PRECISION.
         */
        public boolean equalsEpsilon(LatLon other) {
                final double p = 1/Projection.MAX_SERVER_PRECISION;
                return Math.abs(lat()-other.lat()) <= p && Math.abs(lon()-other.lon()) <= p;
        }

        /**
         * @return <code>true</code>, if the coordinate is outside the world, compared
         * by using lat/lon.
         */
        public boolean isOutSideWorld() {
                return lat() < -Projection.MAX_LAT || lat() > Projection.MAX_LAT || 
                        lon() < -Projection.MAX_LON || lon() > Projection.MAX_LON;
        }

        /**
         * @return <code>true</code> if this is within the given bounding box.
         */
        public boolean isWithin(Bounds b) {
                return lat() >= b.min.lat() && lat() <= b.max.lat() && lon() > b.min.lon() && lon() < b.max.lon();
        }
        
        /**
         * Computes the distance between this lat/lon and another point on the earth.
         * Uses spherical law of cosines formula, not Haversine.
         * @param other the other point.
         * @return distance in metres.
         */
        public double greatCircleDistance(LatLon other) {
                return (Math.acos(
                        Math.sin(Math.toRadians(lat())) * Math.sin(Math.toRadians(other.lat())) + 
                    Math.cos(Math.toRadians(lat()))*Math.cos(Math.toRadians(other.lat())) *
                                  Math.cos(Math.toRadians(other.lon()-lon()))) * 6378135);
        }
        
        /**
         * Returns the heading, in radians, that you have to use to get from 
         * this lat/lon to another.
         * 
         * @param other the "destination" position
         * @return heading 
         */
        public double heading(LatLon other) {
                double rv;
                if (other.lat() == lat()) {
                        rv = (other.lon()>lon() ? Math.PI / 2 : Math.PI * 3 / 2);
                } else {
                        rv = Math.atan((other.lon()-lon())/(other.lat()-lat()));
                        if (rv < 0) rv += Math.PI;
                        if (other.lon() < lon()) rv += Math.PI;
                }
                return rv;
        }

        /**
         * Returns this lat/lon pair in human-readable format.
         * 
         * @return String in the format "lat=1.23456°, lon=2.34567°"
         */
        public String toDisplayString() {
                NumberFormat nf = NumberFormat.getInstance();
                nf.setMaximumFractionDigits(5);
                return "lat=" + nf.format(lat()) + "°, lon=" + nf.format(lon()) + "°";
        }
        
        @Override public String toString() {
                return "LatLon[lat="+lat()+",lon="+lon()+"]";
    }
}