source: stable/HeuristicLab.GeoIP/1.12/Location.cs @ 10352

/**
 * Location.cs
 *
 * Copyright (C) 2008 MaxMind 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */


using System;
using System.IO;
//using System.Math;

public class Location {
    public String countryCode;
    public String countryName;
    public String region;
    public String city;
    public String postalCode;
    public double latitude;
    public double longitude;
    public int dma_code;
    public int area_code;
    public String regionName;
    public int metro_code;

    private static double EARTH_DIAMETER = 2 * 6378.2;
    private static double PI = 3.14159265;
    private static double RAD_CONVERT = PI / 180;

    public double distance (Location loc) {
        double delta_lat, delta_lon;
        double temp;

        double lat1 = latitude;
        double lon1 = longitude;
        double lat2 = loc.latitude;
        double lon2 = loc.longitude;

        // convert degrees to radians
        lat1 *= RAD_CONVERT;
        lat2 *= RAD_CONVERT;

        // find the deltas
        delta_lat = lat2 - lat1;
        delta_lon = (lon2 - lon1) * RAD_CONVERT;

        // Find the great circle distance
        temp = Math.Pow(Math.Sin(delta_lat/2),2) + Math.Cos(lat1) * Math.Cos(lat2) * Math.Pow(Math.Sin(delta_lon/2),2);
        return EARTH_DIAMETER * Math.Atan2(Math.Sqrt(temp),Math.Sqrt(1-temp));
    }
}