/* If all waypoints are with a 20m radius of their centre consider there to be no movement */
private bool HaveWaypointsMoved()
{
float averageLat = Waypoints.Average(info => info.Lat);
float averageLng = Waypoints.Average(info => info.Lng);
foreach (var waypoint in Waypoints)
{
if (GPRMCInfo.Haversine(averageLat, averageLng, waypoint.Lat, waypoint.Lng) > 20)
{
return(true);
}
}
return(false);
}
/* Attempt to parse te NMEA message using regular expressions */
public static GPRMCInfo Parse(string gprmc)
{
Regex regex = new Regex(@"\$GPRMC,(.*),(.*),(.*),(.*),(.*),(.*),(.*),(.*),(.*),(.*),(.*),(.*)");
Match match = regex.Match(gprmc);
if (match.Success)
{
if (match.Groups.Count < 11)
{
return(null);
}
var time = match.Groups[1].Value;
var status = match.Groups[2].Value;
var lat = match.Groups[3].Value;
var latDirection = match.Groups[4].Value;
var lng = match.Groups[5].Value;
var lngDirection = match.Groups[6].Value;
var speed = match.Groups[7].Value;
var trackAngle = match.Groups[8].Value;
var date = match.Groups[9].Value;
var magneticVariation = match.Groups[10].Value;
var checksum = match.Groups[11].Value;
GPRMCInfo result = new GPRMCInfo();
try {
result.Date = DateTime.ParseExact(date + time, "ddMMyyHHmmss.ff", CultureInfo.InvariantCulture);
result.Lat = ParseCoord(lat) * (latDirection == "N" ? 1 : -1);
result.Lng = ParseCoord(lng) * (lngDirection == "E" ? 1 : -1);
result.Speed = float.Parse(speed) * 0.514444f;
} catch {
return(null);
}
return(result);
}
return(null);
}
public async void Run(IBackgroundTaskInstance taskInstance)
{
BackgroundTaskDeferral deferral = taskInstance.GetDeferral();
/* Look for the serial and create a data reader using it's input stream */
string deviceSelector = SerialDevice.GetDeviceSelector("UART0");
var devices = await DeviceInformation.FindAllAsync(deviceSelector);
SerialDevice serialPort = await SerialDevice.FromIdAsync(devices[0].Id);
var DataReader = new DataReader(serialPort.InputStream)
{
InputStreamOptions = InputStreamOptions.Partial
};
bool quit = false;
LineQueue lineQueue = new LineQueue();
while (!quit)
{
/* Read the GPS data from the serial device (the GPS model continously sends NMEA hence only reading is required) */
string gpsData = await ReadAsync(DataReader);
lineQueue.AddChunk(gpsData);
while (lineQueue.HasMore())
{
string nmeaSentence = lineQueue.Next();
Debug.Write(nmeaSentence);
/* Attempt to parse the NMEA sentence if valid add to waypoint list */
if (nmeaSentence.StartsWith("$GPRMC"))
{
GPRMCInfo info = GPRMCInfo.Parse(nmeaSentence);
if (info != null)
{
TimeOfLastValidWaypoint = DateTime.Now;
Waypoints.Add(info);
}
}
/* If the waypoint list is full then check whether there has been any movement and start/end trip as appropriate */
if (Waypoints.Count == Waypoints.Capacity)
{
if (!HaveWaypointsMoved())
{
EndTrip();
}
else
{
if (!InTrip)
{
StartTrip();
}
WriteWaypointsToFile();
}
Waypoints.Clear();
}
/* If there haven't been any valid GPRMC messages for 2min end the trip */
if ((TimeOfLastValidWaypoint - DateTime.Now).Minutes >= 2)
{
EndTrip();
}
}
}
deferral.Complete();
}
