C# อยากทราบวิธีเขียน GPS ติดตามอ่ะครับ ช่วยหน่อยครับ

/// <summary>
/// Try to update present position if the port is setup correctly
/// and the GPS device is returning values
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void timer1_Tick(object sender, EventArgs e)
{
    if (serialPort1.IsOpen)
    {
        string data = serialPort1.ReadExisting();
        string[] strArr = data.Split('$');
        for (int i = 0; i < strArr.Length; i++)
        {
            string strTemp = strArr[i];
            string[] lineArr = strTemp.Split(',');
            if (lineArr[0] == "GPGGA")
            {
                try
                {
                    //Latitude
                    Double dLat = Convert.ToDouble(lineArr[2]);
                    dLat = dLat / 100;
                    string[] lat = dLat.ToString().Split('.');
                    Latitude = lineArr[3].ToString() +
                    lat[0].ToString() + "." +
                    ((Convert.ToDouble(lat[1]) /
                    60)).ToString("#####");

                    //Longitude
                    Double dLon = Convert.ToDouble(lineArr[4]);
                    dLon = dLon / 100;
                    string[] lon = dLon.ToString().Split('.');
                    Longitude = lineArr[5].ToString() +
                    lon[0].ToString() + "." +
                    ((Convert.ToDouble(lon[1]) /
                    60)).ToString("#####");

                    //Display
                    txtLat.Text = Latitude;
                    txtLong.Text = Longitude;

                    btnMapIt.Enabled = true;
                }
                catch
                {
                    //Cannot Read GPS values
                    txtLat.Text = "GPS Unavailable";
                    txtLong.Text = "GPS Unavailable";
                    btnMapIt.Enabled = false;
                }
            }
        }
    }
    else
    {
        txtLat.Text = "COM Port Closed";
        txtLong.Text = "COM Port Closed";
        btnMapIt.Enabled = false;
    }
}