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Lat Lon problem URGENT HELP

This is a discussion on Lat Lon problem URGENT HELP within the MapPoint Desktop Discussion forums, part of the Map Forums category; Hi, I'm using in VB program the following function to get Lat and Lon, but if I execute it more ...

  1. #1
    Abilio Serafim is offline Junior Member White Belt
    Join Date
    Apr 2005
    Posts
    6

    Lat Lon problem URGENT HELP

    Hi,

    I'm using in VB program the following function to get Lat and Lon, but if I execute it more than once I retrieve the error
    "Method Distance of object _Map failed.

    I retrieve the error in this line
    dblLat = 90 - 180 * objMap.Distance(locNorthPole, locX) / dblHalfEarth


    Sub CalcPos(objMap As MapPoint.Map, locX As MapPoint.Location, dblLat As Double, 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
    Set locNorthPole = objMap.GetLocation(90, 0)
    Set 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

    Lat = dblLat
    Lon = dblLon

    End Sub
    Thanks

  2. #2
    Wilfried is offline Senior Member Black Belt
    Join Date
    Nov 2004
    Location
    Belgium
    Posts
    2,433
    Hi,

    This code is ok if you have nothing changed on it. It is widely used in VB and other languages. You should check what is wrong with objMap. When you start to debug first thing to try is other method calls on it. they probably will fail also. Then you have to check out what is changed between the 2 function calls. Also check in debugger if all varialbles are still valid.

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