现在我有一些经纬度的坐标，需要转换成大地坐标，还请vb大虾们帮帮忙，我自己找了一点代码，但是看不懂，如果能帮我改出来也不胜感激！
Public Function Distance(lon1 As Double, lat1 As Double, lon2 As Double, lat2 As Double) As Double
Dim a_2d As Double
Dim e_2d As Double
Dim h_2d As Integer
Dim DEG_2_RAD As Double
Dim RAD_2_DEG As Double
Dim x_rads As Double
Dim y_rads As Double
Dim n_2ds As Double
Dim x_2d As Double
Dim y_2d As Double
Dim z_2d As Double
Dim x_radm As Double
Dim y_radm As Double
Dim n_2dm As Double
Dim x_2d_mark As Double
Dim y_2d_mark As Double
Dim z_2d_mark As Double
Dim curdistance As Double
a_2d = 6378137
e_2d = 0.00669438
h_2d = 15
DEG_2_RAD = 0.01745329252
RAD_2_DEG = 57.2957795129
x_rads = Abs(lon1) * DEG_2_RAD
y_rads = Abs(lat1) * DEG_2_RAD
n_2ds = a_2d / Sqr(1 - e_2d * Sin(y_rads) * Sin(y_rads))
x_2d = (n_2ds + h_2d) * Cos(y_rads) * Cos(x_rads)
y_2d = (n_2ds + h_2d) * Cos(y_rads) * Sin(x_rads)
z_2d = (n_2ds * (1 - e_2d) + h_2d) * Sin(y_rads)
x_radm = Abs(lon2) * DEG_2_RAD
y_radm = Abs(lat2) * DEG_2_RAD
n_2dm = a_2d / Sqr(1 - e_2d * Sin(y_radm) * Sin(y_radm))
x_2d_mark = (n_2dm + h_2d) * Cos(y_radm) * Cos(x_radm)
y_2d_mark = (n_2dm + h_2d) * Cos(y_radm) * Sin(x_radm)
z_2d_mark = (n_2dm * (1 - e_2d) + h_2d) * Sin(y_radm)
curdistance = (x_2d_mark - x_2d) * (x_2d_mark - x_2d) + (y_2d_mark - y_2d) * (y_2d_mark - y_2d) + (z_2d_mark - z_2d) * (z_2d_mark - z_2d)
curdistance = Sqr(curdistance)
Distance = curdistance
End Function