public static int DistanceToGeoPositionMeters(this IGeographicPosition pos1, IGeographicPosition pos2)
{
var dLat = deg2rad(pos2.PositionLatDegrees - pos1.PositionLatDegrees);
var dLon = deg2rad(pos2.PositionLonDegrees - pos1.PositionLonDegrees);
var lat1 = deg2rad(pos1.PositionLatDegrees);
var lat2 = deg2rad(pos2.PositionLatDegrees);
var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) + Math.Sin(dLon / 2) * Math.Sin(dLon / 2) * Math.Cos(lat1) * Math.Cos(lat2);
var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
return (int) Math.Round(meanEarthRadius * c * 1000);
}
/// <summary>
/// Subscribe an observation point (lat / lon / elevation) and attach a callback for detected events.
/// </summary>
/// <param name="airfieldKey">a definable key</param>
/// <param name="airfieldPosition">position and elevation of the observation point (usually an airfield)</param>
/// <param name="eventDetectedCallback">callback on event detected</param>
public void SubscribeAirfieldForMovmentEvents(string airfieldKey, IGeographicPosition airfieldPosition, Action<AircraftTrackEvent> eventDetectedCallback = null)
{
if(airfieldSubscriptions.ContainsKey(airfieldKey))
{
if(eventDetectedCallback != null)
airfieldSubscriptions[airfieldKey].EventDetected += eventDetectedCallback;
return;
}
var subscription = new AirfieldSubscription { AirfieldKey = airfieldKey, AirfieldPosition = airfieldPosition };
if (eventDetectedCallback != null)
subscription.EventDetected += eventDetectedCallback;
airfieldSubscriptions.Add(airfieldKey, subscription);
}
public static float InitialBearingToGeoPositionDegrees(this IGeographicPosition pos1, IGeographicPosition pos2)
{
var lat1 = deg2rad(pos1.PositionLatDegrees); // φ1
var lat2 = deg2rad(pos2.PositionLatDegrees); // φ2
var lon1 = deg2rad(pos1.PositionLonDegrees); // λ1
var lon2 = deg2rad(pos2.PositionLonDegrees); // λ2
var dLat = deg2rad(pos2.PositionLatDegrees - pos1.PositionLatDegrees); // Δφ
var dLon = deg2rad(pos2.PositionLonDegrees - pos1.PositionLonDegrees); // Δλ
var y = Math.Sin(dLon) * Math.Cos(lat2);
var x = Math.Cos(lat1) * Math.Sin(lat2) - Math.Sin(lat1) * Math.Cos(lat2) * Math.Cos(dLon);
var bearing = rad2deg(Math.Atan2(y, x));
if (bearing < 0d)
bearing += 360d;
return (float) Math.Round(bearing, 1);
}
public static IEnumerable<AircraftTrackEvent> DetectTrackEvents(this CircularFifoBuffer<AircraftBeaconSpeedAndTrack> fifoBuffer, DateTime evalDateTimeUtc, TimeSpan maxTimeSpan, IGeographicPosition eventTargetCenter)
{
var events = new List<AircraftTrackEvent>();
List<AircraftBeaconSpeedAndTrack> evalWindow = fifoBuffer.extractAndReverseBufferForEvalWindow(evalDateTimeUtc, maxTimeSpan, getAlreadyAnalysed: true);
// we need 4 beacons to detect - two one state - two other state
if (evalWindow.Count < 4)
return events;
int i = 0;
while(++i <= evalWindow.Count - 4)
{
var subWindow = evalWindow.Skip(i).Take(4).ToArray();
// accuracy check
if (subWindow[3].PositionTimeUTC.Subtract(subWindow[0].PositionTimeUTC).TotalSeconds > accuracyCheck4BeaconsMaxTimeSpanSeconds)
continue;
bool landing = subWindow[0].isMoving()
&& subWindow[1].isMoving()
&& subWindow[2].isStoppedOnGround(eventTargetCenter.PositionAltitudeMeters)
&& subWindow[2].isWithinRefPositionRange(eventTargetCenter)
&& subWindow[3].isStoppedOnGround(eventTargetCenter.PositionAltitudeMeters)
&& subWindow[3].isWithinRefPositionRange(eventTargetCenter);
if (landing)
events.Add(new AircraftTrackEvent { EventType = AircraftTrackEventTypes.Landing, EventDateTimeUTC = subWindow[2].PositionTimeUTC, ReferenceBeacon = subWindow[2] });
bool takeOff = subWindow[0].isStoppedOnGround(eventTargetCenter.PositionAltitudeMeters)
&& subWindow[0].isWithinRefPositionRange(eventTargetCenter)
&& subWindow[1].isStoppedOnGround(eventTargetCenter.PositionAltitudeMeters)
&& subWindow[1].isWithinRefPositionRange(eventTargetCenter)
&& subWindow[2].isMoving()
&& subWindow[3].isMoving();
if (takeOff)
events.Add(new AircraftTrackEvent { EventType = AircraftTrackEventTypes.TakeOff, EventDateTimeUTC = subWindow[1].PositionTimeUTC, ReferenceBeacon = subWindow[2] });
}
return events.Distinct(new AircraftTrackEventComparer());
}
private static bool isWithinRefPositionRange(this AircraftBeaconSpeedAndTrack beacon, IGeographicPosition refPos) => beacon.DistanceToGeoPositionMeters(refPos) <= airportRangeRadiusMeters;
