计算经度纬度两点间的距离

Public Function rad(d)
rad = d * 3.1415926 / 180
End Function

Public Function ASin(ByVal Number As Double) As Double
ASin = Atn(Number / Sqr(-Number * Number + 1))
End Function
Public Function d(lng1, lat1, lng2, lat2)

er = 6378.137
radLat1 = rad(lat1)
radLat2 = rad(lat2)
a = radLat1 - radLat2
b = rad(lng1) - rad(lng2)
s = 2 * ASin(Sqr(Sin(a / 2) * Sin(a / 2)) + Cos(radLat1) * Cos(radLat2) * Sin(b / 2) * Sin(b / 2))
s = s * er
s = Round(s * 10000) / 10000
d = s
End Function

当纬度相差1°时，距离为111.几
问题：当经度相差1°，距离为0.几，理论上也应该在111。几左右，不知道公式什么地方有问题。