/*
* 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;
}
}