Public Function Bearing(ByRef Lat1 As Double, ByRef Lng1 As Double, ByRef Lat2 As Double, ByRef Lng2 As Double) As Double
    Dim x As Double
    Dim y As Double

    Const PI As Double = 3.14159265358979
    Const PIdiv2 As Double = PI / 2#
    Const PIdiv4 As Double = PI / 4#
    Const PImul2 As Double = PI * 2#
    Const div180mulPI = 1# / 180# * PI          ' DegToRad()
    Const div180mulPIdiv2 = div180mulPI / 2#    ' DegToRad() / 2
    Const mul180divPI = 1# * 180# / PI          ' RadToDeg()

    x = Log(Tan((Lat2 * div180mulPIdiv2) + PIdiv4) / Tan((Lat1 * div180mulPIdiv2) + PIdiv4))
    y = (Lng2 - Lng1) * div180mulPI
    If Abs(y) > PI Then
        If y > 0# Then
            y = PImul2 - y
        Else
            y = PImul2 + y
        End If
    End If
    
    ' Bearing = atan2(y, x) * mul180divPI -> atan2() gibt's in VB nicht, deshalb:
    If Abs(y) < 0.0000001 Then
        If x < 0# Then
            Bearing = 180#
        'Else
        '    Bearing = 0#
        End If
    ElseIf Abs(x) < 0.0000001 Then
        If y < 0# Then
            Bearing = 270#
        Else
            Bearing = 90#
        End If
    Else
        Bearing = Atn(y / x) * mul180divPI
        If Bearing < 0# Then
            If x < 0# Then
                Bearing = Bearing + 180#
            Else
                Bearing = Bearing + 360#
            End If
        Else
            If y < 0# Then Bearing = Bearing + 180#
        End If
    End If
End Function