GpxDistanceCalculator.java

package com.github.signed.sandbox.gpx;

public class GpxDistanceCalculator {

    public double distanceInKilometers(double lat1, double lon1, double lat2, double lon2) {
        double theta = lon1 - lon2;
        double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
        dist = Math.acos(dist);
        dist = rad2deg(dist);
        dist = dist * 60 * 1.1515;
        return dist * 1.609344;
    }

    private double rad2deg(double rad) {
        return (rad * 180 / Math.PI);
    }

    private double deg2rad(double deg) {
        return (deg * Math.PI / 180.0);
    }
}