protected override IEnumerable <Datum> Poll()
{
lock (_locker)
{
Position currentPosition = GpsReceiver.Get().GetReading();
Datum[] data = null;
if (_previousPosition == null || currentPosition == null || currentPosition.Timestamp == _previousPosition.Timestamp)
{
data = new Datum[] { }
}
;
else
{
// http://www.movable-type.co.uk/scripts/latlong.html
double φ1 = DegreesToRadians(_previousPosition.Latitude);
double φ2 = DegreesToRadians(currentPosition.Latitude);
double Δφ = DegreesToRadians(currentPosition.Latitude - _previousPosition.Latitude);
double Δλ = DegreesToRadians(currentPosition.Longitude - _previousPosition.Longitude);
double a = Math.Pow(Math.Sin(Δφ / 2), 2) +
Math.Cos(φ1) *
Math.Cos(φ2) *
Math.Pow(Math.Sin(Δλ / 2), 2);
var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
var reportedDistKM = 6371 * c;
double elapsedHours = new TimeSpan(currentPosition.Timestamp.Ticks - _previousPosition.Timestamp.Ticks).TotalHours;
double reportedSpeedKPH = reportedDistKM / elapsedHours;
float accuracy = 0;
if (_previousPosition.Accuracy >= 0 && currentPosition.Accuracy >= 0)
{
double maxDistKM = reportedDistKM + _previousPosition.Accuracy / 1000f + currentPosition.Accuracy / 1000f;
double maxSpeedKPH = maxDistKM / elapsedHours;
accuracy = (float)(maxSpeedKPH - reportedSpeedKPH);
}
data = new SpeedDatum[] { new SpeedDatum(currentPosition.Timestamp, accuracy, (float)reportedSpeedKPH) };
}
if (currentPosition != null)
{
_previousPosition = currentPosition;
}
return(data);
}
}
public SpeedDatum(DateTimeOffset timestamp, Position previousPosition, Position currentPosition)
: base(timestamp, 0)
{
double distanceKM;
double timeHours;
_kph = SpeedDatum.CalculateSpeedKPH(previousPosition, currentPosition, out distanceKM, out timeHours);
if (previousPosition.Accuracy >= 0 && currentPosition.Accuracy >= 0)
{
double maximumDistanceKM = distanceKM + previousPosition.Accuracy / 1000f + currentPosition.Accuracy / 1000f;
double maximumSpeedKPH = maximumDistanceKM / timeHours;
Accuracy = (float)(maximumSpeedKPH - _kph);
}
}
protected override IEnumerable <Datum> Poll(CancellationToken cancellationToken)
{
lock (_locker)
{
Position currentPosition = null;
try
{
currentPosition = GpsReceiver.Get().GetReading(cancellationToken);
}
catch (Exception ex)
{
SensusServiceHelper.Get().Logger.Log("Failed to get GPS reading: " + ex.Message, LoggingLevel.Normal, GetType());
}
SpeedDatum datum = null;
if (currentPosition != null)
{
if (_previousPosition == null)
{
_previousPosition = currentPosition;
}
else if (currentPosition.Timestamp > _previousPosition.Timestamp) // it has happened (rarely) that positions come in out of order...drop any such positions.
{
datum = new SpeedDatum(currentPosition.Timestamp, _previousPosition, currentPosition);
_previousPosition = currentPosition;
}
}
if (datum == null)
{
return new Datum[] { }
}
;
else
{
return new Datum[] { datum }
};
}
}
protected override IEnumerable<Datum> Poll(CancellationToken cancellationToken)
{
lock (_locker)
{
SpeedDatum datum = null;
Position currentPosition = GpsReceiver.Get().GetReading(cancellationToken);
if (currentPosition == null)
throw new Exception("Failed to get GPS reading.");
else
{
if (_previousPosition == null)
_previousPosition = currentPosition;
else if (currentPosition.Timestamp > _previousPosition.Timestamp) // it has happened (rarely) that positions come in out of order...drop any such positions.
{
datum = new SpeedDatum(currentPosition.Timestamp, _previousPosition, currentPosition);
_previousPosition = currentPosition;
}
}
if (datum == null)
return new Datum[] { }; // datum will be null on the first poll and where polls return locations out of order (rare). these should count toward participation.
else
return new Datum[] { datum };
}
}
protected override IEnumerable<Datum> Poll(CancellationToken cancellationToken)
{
lock (_locker)
{
Position currentPosition = GpsReceiver.Get().GetReading(cancellationToken);
Datum[] data = null;
if (_previousPosition == null || currentPosition == null || currentPosition.Timestamp == _previousPosition.Timestamp)
data = new Datum[] { };
else
data = new SpeedDatum[] { new SpeedDatum(currentPosition.Timestamp, _previousPosition, currentPosition) };
if (currentPosition != null)
_previousPosition = currentPosition;
return data;
}
}
protected override IEnumerable<Datum> Poll(CancellationToken cancellationToken)
{
lock (_locker)
{
Position currentPosition = null;
try
{
currentPosition = GpsReceiver.Get().GetReading(cancellationToken);
}
catch (Exception ex)
{
SensusServiceHelper.Get().Logger.Log("Failed to get GPS reading: " + ex.Message, LoggingLevel.Normal, GetType());
}
SpeedDatum datum = null;
if (currentPosition != null)
{
if (_previousPosition == null)
_previousPosition = currentPosition;
else if (currentPosition.Timestamp > _previousPosition.Timestamp) // it has happened (rarely) that positions come in out of order...drop any such positions.
{
datum = new SpeedDatum(currentPosition.Timestamp, _previousPosition, currentPosition);
_previousPosition = currentPosition;
}
}
if (datum == null)
return new Datum[] { };
else
return new Datum[] { datum };
}
}
