ETA programming struggle

[AirFlow]

Hey Team,

 

I have been racking my brain for the past 2 days trying to deep dive into programming an accurate and effective ETA system. 

Using VB.net and the harvestine theory formula to calculate the remaining time until destination. I am pulling the user's current Position (latitude and longitude) via a timer then inputting that into the following:

 

Public Sub CalculateAndDisplayETA()


        Dim xmlFile As String = My.Settings.ApplicationDirectory + "\Routes\" + IFETabletLrg.DepartureLbl.Text + IFETabletLrg.ArrivalLbl.Text + ".xml"

        ' Load the XML file that contains route information
        Dim xmlDoc As New XmlDocument()
        xmlDoc.Load(xmlFile)

        ' Find the <destination> element
        Dim destinationNode As XmlNode = xmlDoc.SelectSingleNode("/OFP/destination")

        ' Check if the <destination> elements exist
        If destinationNode IsNot Nothing Then
            ' Extract the values from the <destination> element
            Dim destinationAirportLat As Double = Double.Parse(destinationNode.SelectSingleNode("pos_lat").InnerText)
            Dim destinationAirportLon As Double = Double.Parse(destinationNode.SelectSingleNode("pos_long").InnerText)

            Dim startLat As Double = IFETabletLrg.UserPosLat  ' Formula Start latitude in degrees (Current User's A/C Lat)
            Dim startLon As Double = IFETabletLrg.userPosLng    ' Formula Start longitude in degrees (Current User's A/C Long)

            Dim endLat As Double = destinationAirportLat   ' Destination latitude in degrees
            Dim endLon As Double = destinationAirportLon   ' Destination longitude in degrees
            Dim speed As Double = ((gspeed.Value / 33714.6311111111) * 1.852)  ' User's Groundspeed

            ' Calculate the distance using the Haversine formula
            Dim distanceNM As Double = HaversineDistance(startLat, startLon, endLat, endLon)

            ' Convert distance to nautical miles to kilometers
            Dim distanceKm As Double = distanceNM * 1.852

            ' Calculate the ETA in hours
            Dim timeHours As Double = distanceKm / speed

            ' Calculate hours and minutes from the total hours (timeHours)
            Dim hours As Integer = CInt(Math.Floor(timeHours))
            Dim minutes As Integer = CInt(Math.Round((timeHours - hours) * 60))

            ' Format the ETA as "hh'h mm'm"
            Dim formattedETA As String = $"{hours:00}h {minutes:00}m"

            ' Display the formatted ETA in the label
            IFETabletLrg.ETALbl.Text = formattedETA
        End If
    End Sub

    Private Function HaversineDistance(startLat As Double, startLon As Double, endLat As Double, endLon As Double) As Double
        ' Convert degrees to radians
        Dim startLatRad As Double = startLat * Math.PI / 180.0
        Dim startLonRad As Double = startLon * Math.PI / 180.0
        Dim endLatRad As Double = endLat * Math.PI / 180.0
        Dim endLonRad As Double = endLon * Math.PI / 180.0

        ' Earth's radius in nautical miles
        Const EarthRadiusNM As Double = 3443.8445

        ' Haversine formula
        Dim dLat As Double = endLatRad - startLatRad
        Dim dLon As Double = endLonRad - startLonRad
        Dim a As Double = Math.Sin(dLat / 2.0) * Math.Sin(dLat / 2.0) + Math.Cos(startLatRad) * Math.Cos(endLatRad) * Math.Sin(dLon / 2.0) * Math.Sin(dLon / 2.0)
        Dim c As Double = 2.0 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a))
        Dim distanceNM As Double = EarthRadiusNM * c

        Return distanceNM
    End Function

 

 

This is returning a result however it seems to be inaccurate when compared to other software such as SmartCars. It is slower by a range of 30 minutes to 90 minutes.

 

Any ideas?

Edited August 7, 2023 by AirFlow

[Paul Henty]

Hi,

I can't see anything obviously wrong. The haversine calculation is giving correct values.

The only thing I can't check is the ground speed conversion:

Dim speed As Double = ((gspeed.Value / 33714.6311111111) * 1.852)  ' User's Groundspeed

Where is gspeed coming from? What units is it in?

Paul