Hi Richard,

Thanks for the response, I have reproduced the rest of the code below, the symptom is that I am not receiving a return from calcpos for the given location (“latitude and longitude are returned as 0”)

Regards,
Joe

' Compute latitude and longitude given a location object
' Author: Gilles Kohl
' (gilles@compuserve.com)
'
' This code is copyrighted freeware - use freely, but please leave this
' header intact. Suggestions and comments welcome.

Function Arccos(ByVal x As Double) As Double
If x = 1 Then
Arccos = 0
Exit Function
End If
Arccos = Atan(-x / Sqrt(-x * x + 1)) + 2 * Atan(1)
End Function

Sub CalcPos(ByVal objMap As MapPoint.Map, ByVal locX As MapPoint.Location, ByVal dblLat As Double, ByVal dblLon As Double)
Static locNorthPole As MapPoint.Location
Static locSantaCruz As MapPoint.Location ' Center of western hemisphere
Static dblHalfEarth As Double ' Half circumference of the earth (as a sphere)
Static dblQuarterEarth As Double ' Quarter circumference of the earth (as a sphere)
Static Pi As Double

' Check if initialization already done
If locNorthPole Is Nothing Then
locNorthPole = objMap.GetLocation(90, 0)
locSantaCruz = objMap.GetLocation(0, -90)

' Compute distance between north and south poles == half earth circumference
dblHalfEarth = objMap.Distance(locNorthPole, objMap.GetLocation(-90, 0))

' Quarter of that is the max distance a point may be away from locSantaCruz and still be in western hemisphere
dblQuarterEarth = dblHalfEarth / 2
Pi = 3.14159265358979
End If

' Compute latitude from distance to north pole
dblLat = 90 - 180 * objMap.Distance(locNorthPole, locX) / dblHalfEarth

Dim l As Double
Dim d As Double

' Compute great circle distance to locX from point on Greenwich meridian and computed Latitude
d = objMap.Distance(objMap.GetLocation(dblLat, 0), locX)

' convert latitude to radian
l = (dblLat / 180) * Pi

' Compute Longitude from great circle distance
dblLon = 180 * Arccos((Cos((d * 2 * Pi) / (2 * dblHalfEarth)) - Sin(l) * Sin(l)) / (Cos(l) * Cos(l))) / Pi

' Correct longitude sign if located in western hemisphere
If objMap.Distance(locSantaCruz, locX) < dblQuarterEarth Then dblLon = -dblLon
End Sub