Android example source code file (GeoUtils.java)

This example Android source code file (GeoUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, earth_radius_km, geopoint, geoutils, maps, million

The GeoUtils.java Android example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.radar;

import com.google.android.maps.GeoPoint;

/**
 * Library for some use useful latitude/longitude math
 */
public class GeoUtils {
    private static int EARTH_RADIUS_KM = 6371;

    public static int MILLION = 1000000;

    /**
     * Computes the distance in kilometers between two points on Earth.
     * 
     * @param lat1 Latitude of the first point
     * @param lon1 Longitude of the first point
     * @param lat2 Latitude of the second point
     * @param lon2 Longitude of the second point
     * @return Distance between the two points in kilometers.
     */
    public static double distanceKm(double lat1, double lon1, double lat2, double lon2) {
        double lat1Rad = Math.toRadians(lat1);
        double lat2Rad = Math.toRadians(lat2);
        double deltaLonRad = Math.toRadians(lon2 - lon1);
        
        return Math.acos(Math.sin(lat1Rad) * Math.sin(lat2Rad) + Math.cos(lat1Rad) * Math.cos(lat2Rad)
                * Math.cos(deltaLonRad))
                * EARTH_RADIUS_KM;
    }
    
    /**
     * Computes the distance in kilometers between two points on Earth.
     * 
     * @param p1 First point
     * @param p2 Second point
     * @return Distance between the two points in kilometers.
     */
    public static double distanceKm(GeoPoint p1, GeoPoint p2) {
        double lat1 = p1.getLatitudeE6() / (double)MILLION;
        double lon1 = p1.getLongitudeE6() / (double)MILLION;
        double lat2 = p2.getLatitudeE6() / (double)MILLION;
        double lon2 = p2.getLongitudeE6() / (double)MILLION;

        return distanceKm(lat1, lon1, lat2, lon2);
    }
    
    /**
     * Computes the bearing in degrees between two points on Earth.
     * 
     * @param p1 First point
     * @param p2 Second point
     * @return Bearing between the two points in degrees. A value of 0 means due
     *         north.
     */
    public static double bearing(GeoPoint p1, GeoPoint p2) {
        double lat1 = p1.getLatitudeE6() / (double) MILLION;
        double lon1 = p1.getLongitudeE6() / (double) MILLION;
        double lat2 = p2.getLatitudeE6() / (double) MILLION;
        double lon2 = p2.getLongitudeE6() / (double) MILLION;

        return bearing(lat1, lon1, lat2, lon2);
    }
    
    /**
     * Computes the bearing in degrees between two points on Earth.
     * 
     * @param lat1 Latitude of the first point
     * @param lon1 Longitude of the first point
     * @param lat2 Latitude of the second point
     * @param lon2 Longitude of the second point
     * @return Bearing between the two points in degrees. A value of 0 means due
     *         north.
     */
    public static double bearing(double lat1, double lon1, double lat2, double lon2) {
        double lat1Rad = Math.toRadians(lat1);
        double lat2Rad = Math.toRadians(lat2);
        double deltaLonRad = Math.toRadians(lon2 - lon1);

        double y = Math.sin(deltaLonRad) * Math.cos(lat2Rad);
        double x = Math.cos(lat1Rad) * Math.sin(lat2Rad) - Math.sin(lat1Rad) * Math.cos(lat2Rad)
                * Math.cos(deltaLonRad);
        return radToBearing(Math.atan2(y, x));
    }
    
    /**
     * Converts an angle in radians to degrees
     */
    public static double radToBearing(double rad) {
        return (Math.toDegrees(rad) + 360) % 360;
    }
}