根据任意两点地图坐标算出距离是多少

 private static double rads(double d)
        {
            return d*Math.PI/180.0;
        }

        private const double EarihRadius = 6378.137;

        private static double GetDistances(double lat1, double lng1, double lat2, double lng2)
        {
            var radLat1 = rads(lat1);
            var radLat2 = rads(lat2);
            var lat = radLat1 - radLat2;
            var lng = rads(lng1) - rads(lng2);
            var s = 2*
                    Math.Asin(
                        Math.Sqrt(Math.Pow(Math.Sin(lat/2), 2) +
                                  Math.Cos(radLat1)*Math.Cos(radLat2)*Math.Pow(Math.Sin(lng/2), 2)));
            s = s*EarihRadius;
            return Math.Round(s*10000)/10000;
        }


///
var c = GetDistances( 39.90408611111111,116.29571388888888, 39.9061185, 116.297728);
            Console.WriteLine(c);