经纬度求距离

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;
}