c#计算两点间距离

 double CalcDistance(Poit from, Poit to)
 {
            double rad = 6371 * 1000; //Earth radius in m
            double p1X = from.X / 180 * Math.PI;
            double p1Y = from.Y / 180 * Math.PI;
            double p2X = to.X / 180 * Math.PI;
            double p2Y = to.Y / 180 * Math.PI;
            double d = Math.Acos(Math.Sin(p1Y) * Math.Sin(p2Y) +
                Math.Cos(p1Y) * Math.Cos(p2Y) * Math.Cos(p2X - p1X)) * rad;

            return d;
  }
  public struct Poit
  {
    public double X;
    public double Y;
  }

给定两点经纬度，计算距离（m)

资料：http://wenku.baidu.com/link?url=-jNNwtuorM4DYE7kk9l9BJRp6TIG6kYxfW86OaMpkYYpeN6aDyOwrPWv5jB5fjCdtPHpwO6kJ0RSYLWqO4v8acpT1eGpBkjJg3jXjI1tJgG