通过两个GPS计算两个GPS点的距离

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 =  * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a/),) +
    Math.Cos(radLat1)*Math.Cos(radLat2)*Math.Pow(Math.Sin(b/),)));
   s = s * EARTH_RADIUS;
   s = Math.Round(s * ) / ;
   return s;
}

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