通過兩個點的經緯度計算距離

 private static double EARTH_RADIUS = 6378.137;
 private static double rad(double d)
 {
    return d * Math.PI / 180.0;
 }

 public static double GetDistance(double lat1, double lng1, double lat2, double lng2)
 {
    double radLat1 = rad(lat1);
    double radLat2 = rad(lat2);
    double a = radLat1 - radLat2;
    double b = rad(lng1) - rad(lng2);
    double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) +
     Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
    s = s * EARTH_RADIUS;
//    s = Math.round(s * 10000) / 10000;
    return s;
 }