001    /**
002     * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
003     *
004     * This library is free software; you can redistribute it and/or modify it under
005     * the terms of the GNU Lesser General Public License as published by the Free
006     * Software Foundation; either version 2.1 of the License, or (at your option)
007     * any later version.
008     *
009     * This library is distributed in the hope that it will be useful, but WITHOUT
010     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
011     * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
012     * details.
013     */
014    
015    package com.liferay.util;
016    
017    /**
018     * @author Brian Wing Shun Chan
019     */
020    public class Distance {
021    
022            public static double calculate(
023                    double lat1, double lon1, double lat2, double lon2) {
024    
025                    // Convert from radians to degrees
026    
027                    lat1 = (Math.PI * lat1) / 180;
028                    lon1 = (Math.PI * lon1) / 180;
029                    lat2 = (Math.PI * lat2) / 180;
030                    lon2 = (Math.PI * lon2) / 180;
031    
032                    double miles =
033                            3963.4 *
034                                    Math.acos(
035                                            (Math.sin(lat1) * Math.sin(lat2)) +
036                                                    (Math.cos(lat1) * Math.cos(lat2) *
037                                                            Math.cos(lon1 - lon2)));
038    
039                    return miles;
040            }
041    
042            public static double kmToMiles(double km) {
043                    return km * 0.621;
044            }
045    
046            public static double milesToKm(double miles) {
047                    return miles / 0.621;
048            }
049    
050    }