Maths.java

/*
 * Copyright (C) 2016 mendhak
 *
 * This file is part of GPSLogger for Android.
 *
 * GPSLogger for Android is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * GPSLogger for Android 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GPSLogger for Android.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.mendhak.gpslogger.common;


import android.location.Location;

public class Maths {
    /**
     * Uses the Haversine formula to calculate the distance (meters) between to lat-long coordinates
     *
     * @param latitude1  The first point's latitude
     * @param longitude1 The first point's longitude
     * @param latitude2  The second point's latitude
     * @param longitude2 The second point's longitude
     * @return The distance between the two points in meters
     */
    public static double calculateDistance(double latitude1, double longitude1, double latitude2, double longitude2) {
        /*
            Haversine formula:
            A = sin²(Δlat/2) + cos(lat1).cos(lat2).sin²(Δlong/2)
            C = 2.atan2(√a, √(1−a))
            D = R.c
            R = radius of earth, 6371 km.
            All angles are in radians
            */

        double deltaLatitude = Math.toRadians(Math.abs(latitude1 - latitude2));
        double deltaLongitude = Math.toRadians(Math.abs(longitude1 - longitude2));
        double latitude1Rad = Math.toRadians(latitude1);
        double latitude2Rad = Math.toRadians(latitude2);

        double a = Math.pow(Math.sin(deltaLatitude / 2), 2) +
                (Math.cos(latitude1Rad) * Math.cos(latitude2Rad) * Math.pow(Math.sin(deltaLongitude / 2), 2));

        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

        return 6371 * c * 1000; //Distance in meters

    }

    /**
     * Converts given meters/second to nautical mile/hour.
     *
     * @param mps meters per second
     * @return knots
     */
    public static double mpsToKnots(double mps) {
        // Google "meters per second to knots"
        return mps * 1.94384449;
    }

    /**
     * Checks bundle in the Location object for satellties used in fix.
     * @param loc The location object to query
     * @return satellites used in fix, or 0 if no value found.
     */
    public static int getBundledSatelliteCount(Location loc){
        int sat = 0;

        if(loc.getExtras() != null){
            sat = loc.getExtras().getInt("satellites",0);

            if (sat == 0) {
                //Provider gave us nothing, let's look at our bundled count
                sat = loc.getExtras().getInt("SATELLITES_FIX", 0);
            }
        }

        return sat;
    }


}