'计算地球上两点之间的距离并输出
Public Function getdistance(ByVal lat1 As Double, ByVal lon1 As Double, ByVal lat2 As Double, ByVal lon2 As Double) As Integer
Static Dim pi As Double = 3.14159265
Static Dim earthrad As Double = 6378137
Static Dim rad As Double = Math.PI / 180.0
Dim radlat1 As Double = lat1 * rad
Dim radlat2 As Double = lat2 * rad
Dim a As Double = radlat1 - radlat2
Dim b As Double = (lon1 - lon2) * rad
Dim s As Double = 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 * 6378137.0
s = Math.Round(s * 10000) / 10000
Return s
End Function