/// <summary>
/// 经纬度之间的距离
/// </summary>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public static double CalcDistance(System.Windows.Point from, System.Windows.Point to)
{
double rad = 6371; //Earth radius in Km
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;
return Math.Acos(Math.Sin(p1Y) * Math.Sin(p2Y) +
Math.Cos(p1Y) * Math.Cos(p2Y) * Math.Cos(p2X - p1X)) * rad;
}