Distance.java

/**
 * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License for more
 * details.
 */

package com.liferay.util;

/**
 * @author Brian Wing Shun Chan
 */
public class Distance {

	public static double calculate(
		double lat1, double lon1, double lat2, double lon2) {

		// Convert from radians to degrees

		lat1 = (Math.PI * lat1) / 180;
		lon1 = (Math.PI * lon1) / 180;
		lat2 = (Math.PI * lat2) / 180;
		lon2 = (Math.PI * lon2) / 180;

		double miles =
			3963.4 *
				Math.acos(
					(Math.sin(lat1) * Math.sin(lat2)) +
						(Math.cos(lat1) * Math.cos(lat2) *
							Math.cos(lon1 - lon2)));

		return miles;
	}

	public static double kmToMiles(double km) {
		return km * 0.621;
	}

	public static double milesToKm(double miles) {
		return miles / 0.621;
	}

}