Converting NMEA sentence Latitude and Longitude to Decimal Degrees

I did some more testing and I must go back on what I have implied. I'm getting some very accurate readings by using the method you posted, imarshad. I don't know what I was doing wrong last week when I was testing this.  For the convenience of anyone else trying to mess with this GPS raw data stuff, here are my VB / VBA functions that you can use to extract the Decimal Degrees from raw NMEA strings. I'm also posting a couple of other simple functions that I'm using.




Public Function fncGetLatitude(strNMEAString As String, strNMEAStringType As String) As String
    'This function extracts the latitude from an NMEA string and converts it to Decimal Degrees (as a string).
    'To use this function you must specify what string type you are passing in, either GPRMC or GPGGA
    Dim aryNMEAString() As String
    aryNMEAString() = Split(strNMEAString, ",")
    Dim sngMinutes As Single, sngLatitude As Single
     
    Select Case strNMEAStringType
     
        Case "GPRMC"
            'Latitude is the Number 3 place in the array (4th place in the string)
            If aryNMEAString(2) = "A" Then 'A represents a valid string
                sngMinutes = (CSng(Mid(aryNMEAString(3), 3, 7)) / 60)
                sngLatitude = CSng(Left(aryNMEAString(3), 2)) + sngMinutes
                fncGetLatitude = CStr(sngLatitude)
            End If
           
        Case "GPGGA"
            'Latitude is the Number 2 place in the array (3rd place in the string)
            If CSng(aryNMEAString(2)) <> 0 Then 'If string is invalid it will be 0
                sngMinutes = (CSng(Mid(aryNMEAString(2), 3, 7)) / 60)
                sngLatitude = CSng(Left(aryNMEAString(2), 2)) + sngMinutes
                fncGetLatitude = CStr(sngLatitude)
            End If
     End Select
End Function



Public Function fncGetLongitude(strNMEAString As String, strNMEAStringType As String) As String
    'This function extracts the longitude from an NMEA string and converts it to Decimal Degrees (as a string).
    'To use this function you must specify what string type you are passing in, either GPRMC or GPGGA
    Dim aryNMEAString() As String
    aryNMEAString() = Split(strNMEAString, ",")
    Dim sngMinutes As Single, sngLongitude As Single
   
    Select Case strNMEAStringType
     
        Case "GPRMC"
            'Latitude is the Number 3 place in the array (4th place in the string)
            If aryNMEAString(2) = "A" Then
                sngMinutes = (CSng(Mid(aryNMEAString(5), 4, 7)) / 60)
                sngLongitude = CSng(Left(aryNMEAString(5), 3)) + sngMinutes
                fncGetLongitude = CStr(sngLongitude)
            End If
           
        Case "GPGGA"
            'Latitude is the Number 2 place in the array (3rd place in the string)
            If CSng(aryNMEAString(4)) <> 0 Then
                sngMinutes = (CSng(Mid(aryNMEAString(4), 4, 7)) / 60)
                sngLongitude = CSng(Left(aryNMEAString(4), 3)) + sngMinutes
                fncGetLongitude = CStr(sngLongitude)
            End If
    End Select
End Function



Public Function fncGetSpeed(strGPRMC As String) As Integer
    Dim aryGPRMC() As String, dblSpeed As Double
    aryGPRMC() = Split(strGPRMC, ",")
    If aryGPRMC(7) <> "" Then dblSpeed = CDbl(aryGPRMC(7))
    fncGetSpeed = CInt(dblSpeed * 1.15077945)
End Function



Public Function fncGetHeading(strGPRMC As String) As Single
    Dim aryGPRMC() As String
    aryGPRMC() = Split(strGPRMC, ",")
    If aryGPRMC(8) <> "" Then fncGetHeading = CSng(aryGPRMC(8))
End Function



Public Function fncGetSatellites(strGPGGA As String) As Integer
    Dim aryGPGGA() As String
    aryGPGGA() = Split(strGPGGA, ",")
    fncGetSatellites = CInt(aryGPGGA(7))
End Function