两个经纬度算距离class Earth{private const double EARTH-RADIUS = 6378

两个经纬度算距离class Earth{private const double EARTH_RADIUS = 6378.137;//地球半径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;}}用的这个算法,现在不知道精度到底如何?这个return的S是米还是千米.我要算50米左右的距离.