/// <summary>
/// Decodes a coarse format TIS-B airborne position message.
/// </summary>
/// <param name="message"></param>
private void DecodeCoarseTisbAirbornePosition(AdsbMessage message)
{
message.MessageFormat = MessageFormat.CoarseTisbAirbornePosition;
var subMessage = message.CoarseTisbAirbornePosition = new CoarseTisbAirbornePosition();
message.TisbIcaoModeAFlag = _BitStream.ReadByte(1);
subMessage.SurveillanceStatus = (SurveillanceStatus)_BitStream.ReadByte(2);
subMessage.ServiceVolumeID = _BitStream.ReadByte(4);
var rawAltitude = _BitStream.ReadUInt16(12);
var acCode = ((rawAltitude & 0xfe0) >> 1) | (rawAltitude & 0x0f);
if ((rawAltitude & 0x10) != 0)
{
subMessage.BarometricAltitude = ModeSAltitudeConversion.CalculateBinaryAltitude(acCode);
}
else
{
subMessage.BarometricAltitude = ModeSAltitudeConversion.LookupGillhamAltitude(acCode);
}
var groundTrackValid = _BitStream.ReadBit();
var groundTrack = _BitStream.ReadByte(5);
var groundSpeed = _BitStream.ReadByte(6);
if (groundTrackValid)
{
subMessage.GroundTrack = (double)groundTrack * 11.25;
}
subMessage.GroundSpeed = (double)groundSpeed * 16.0;
subMessage.CompactPosition = ExtractCprCoordinate(message, 12, ignoreMessageType: true);
}
/// <summary>
/// Decodes a surface position message.
/// </summary>
/// <param name="message"></param>
private void DecodeSurfacePosition(AdsbMessage message)
{
message.MessageFormat = MessageFormat.SurfacePosition;
var subMessage = message.SurfacePosition = new SurfacePositionMessage();
var movement = _BitStream.ReadByte(7);
if (movement > 0)
{
if (movement < 124)
{
subMessage.GroundSpeed = _SurfaceGroundSpeed[movement];
}
else if (movement == 124)
{
subMessage.GroundSpeed = 175.0;
subMessage.GroundSpeedExceeded = true;
}
else if (movement == 127)
{
subMessage.IsReversing = true;
}
}
var trackIsValid = _BitStream.ReadBit();
var track = _BitStream.ReadByte(7);
if (trackIsValid)
{
subMessage.GroundTrack = track * 2.8125;
}
subMessage.PositionTimeIsExact = _BitStream.ReadBit();
subMessage.CompactPosition = ExtractCprCoordinate(message, 19);
}
/// <summary>
/// Decodes an identification and emitter category message.
/// </summary>
/// <param name="message"></param>
private void DecodeIdentification(AdsbMessage message)
{
message.MessageFormat = MessageFormat.IdentificationAndCategory;
var subMessage = message.IdentifierAndCategory = new IdentifierAndCategoryMessage();
subMessage.EmitterCategory = _EmitterCategories[message.Type - 1, _BitStream.ReadByte(3)];
subMessage.Identification = ModeSCharacterTranslator.ExtractCharacters(_BitStream, 8);
}
public void ModeSMessageEventArgs_Constructor_Initialises_To_Known_State()
{
var dateTimeNow = DateTime.UtcNow;
var message = new ModeSMessage();
var adsbMessage = new AdsbMessage(message);
var eventArgs = new ModeSMessageEventArgs(dateTimeNow, message, adsbMessage);
Assert.AreEqual(dateTimeNow, eventArgs.ReceivedUtc);
Assert.AreSame(message, eventArgs.ModeSMessage);
Assert.AreSame(adsbMessage, eventArgs.AdsbMessage);
}
/// <summary>
/// Extracts the fields describing a Compact Position Reporting coordinate in a message.
/// </summary>
/// <param name="message"></param>
/// <param name="encodingBits"></param>
/// <returns></returns>
private CompactPositionReportingCoordinate ExtractCprCoordinate(AdsbMessage message, byte encodingBits)
{
CompactPositionReportingCoordinate result = null;
if (message.Type != 0)
{
bool isOddFormat = _BitStream.ReadBit();
int latitude = (int)_BitStream.ReadUInt32(17);
int longitude = (int)_BitStream.ReadUInt32(17);
result = new CompactPositionReportingCoordinate(latitude, longitude, isOddFormat, encodingBits);
}
return(result);
}
/// <summary>
/// Extracts the fields describing a Compact Position Reporting coordinate in a message.
/// </summary>
/// <param name="message"></param>
/// <param name="encodingBits"></param>
/// <param name="ignoreMessageType"></param>
/// <returns></returns>
private CompactPositionReportingCoordinate ExtractCprCoordinate(AdsbMessage message, byte encodingBits, bool ignoreMessageType = false)
{
CompactPositionReportingCoordinate result = null;
var readBits = encodingBits >= 17 ? 17 : encodingBits;
if (message.Type != 0 || ignoreMessageType)
{
bool isOddFormat = _BitStream.ReadBit();
int latitude = (int)_BitStream.ReadUInt32(readBits);
int longitude = (int)_BitStream.ReadUInt32(readBits);
result = new CompactPositionReportingCoordinate(latitude, longitude, isOddFormat, encodingBits);
}
return(result);
}
/// <summary>
/// Decodes an identification and emitter category message.
/// </summary>
/// <param name="message"></param>
private void DecodeIdentification(AdsbMessage message)
{
message.MessageFormat = MessageFormat.IdentificationAndCategory;
var subMessage = message.IdentifierAndCategory = new IdentifierAndCategoryMessage();
subMessage.EmitterCategory = _EmitterCategories[message.Type - 1, _BitStream.ReadByte(3)];
subMessage.Identification = ModeSCharacterTranslator.ExtractCharacters(_BitStream, 8);
if (IsFineFormatTisb(message))
{
// These are only sent for TIS-B fine format messages with a valid ICAO24, in which case the
// IMF flag can be assumed to be zero
message.TisbIcaoModeAFlag = 0;
}
}
/// <summary>
/// Decodes an airborne position message.
/// </summary>
/// <param name="message"></param>
private void DecodeAirbornePosition(AdsbMessage message)
{
message.MessageFormat = message.Type == 0 ? MessageFormat.NoPositionInformation : MessageFormat.AirbornePosition;
var subMessage = message.AirbornePosition = new AirbornePositionMessage();
subMessage.SurveillanceStatus = (SurveillanceStatus)_BitStream.ReadByte(2);
if (IsFineFormatTisb(message))
{
message.TisbIcaoModeAFlag = _BitStream.ReadByte(1);
}
else
{
if (message.Type == 0)
{
_BitStream.Skip(1);
}
else
{
subMessage.NicB = (byte)(_BitStream.ReadBit() ? 2 : 0);
}
}
var rawAltitude = _BitStream.ReadUInt16(12);
var acCode = ((rawAltitude & 0xfe0) >> 1) | (rawAltitude & 0x0f);
int?altitude = null;
if ((rawAltitude & 0x10) != 0)
{
altitude = ModeSAltitudeConversion.CalculateBinaryAltitude(acCode);
}
else
{
altitude = ModeSAltitudeConversion.LookupGillhamAltitude(acCode);
}
if (message.Type < 20)
{
subMessage.BarometricAltitude = altitude;
}
else
{
subMessage.GeometricAltitude = altitude;
}
subMessage.PositionTimeIsExact = _BitStream.ReadBit();
subMessage.CompactPosition = ExtractCprCoordinate(message, 17);
}
public void AdsbMessage_Constructor_Initialises_To_Known_Values_And_Properties_Work()
{
var modeSMessage = new ModeSMessage();
var message = new AdsbMessage(modeSMessage);
Assert.AreSame(modeSMessage, message.ModeSMessage);
TestUtilities.TestProperty(message, m => m.AirbornePosition, null, new AirbornePositionMessage());
TestUtilities.TestProperty(message, m => m.AirborneVelocity, null, new AirborneVelocityMessage());
TestUtilities.TestProperty(message, m => m.IdentifierAndCategory, null, new IdentifierAndCategoryMessage());
TestUtilities.TestProperty(message, m => m.MessageFormat, MessageFormat.None, MessageFormat.AircraftOperationalStatus);
TestUtilities.TestProperty(message, m => m.SurfacePosition, null, new SurfacePositionMessage());
TestUtilities.TestProperty(message, m => m.TargetStateAndStatus, null, new TargetStateAndStatusMessage());
TestUtilities.TestProperty(message, m => m.Type, (byte)0, (byte)255);
TestUtilities.TestProperty(message, m => m.AircraftStatus, null, new AircraftStatusMessage());
TestUtilities.TestProperty(message, m => m.AircraftOperationalStatus, null, new AircraftOperationalStatusMessage());
}
private void UpdateView(AdsbMessage message)
{
string key = message.ModeSMessage.FormattedIcao24;
if (message.ModeSMessage.Identity.HasValue)
{
UpdateViewModelField(key, "Squawk", message.ModeSMessage.Identity.Value.ToString("0000"));
}
switch (message.MessageFormat)
{
case MessageFormat.IdentificationAndCategory:
UpdateViewModelField(key, "Identification", message.IdentifierAndCategory.Identification);
UpdateViewModelField(key, "Category", message.IdentifierAndCategory.EmitterCategory.ToString());
break;
case MessageFormat.AirborneVelocity:
if (message.AirborneVelocity.VectorVelocity != null && message.AirborneVelocity.VectorVelocity.Speed.HasValue)
{
UpdateViewModelField(key, "AirborneVelocity", Math.Round(message.AirborneVelocity.VectorVelocity.Speed.Value, 0, MidpointRounding.AwayFromZero).ToString());
}
break;
case MessageFormat.AircraftOperationalStatus:
UpdateViewModelField(key, "SIL", message.AircraftOperationalStatus.Sil.ToString());
UpdateViewModelField(key, "SDA",
message.AircraftOperationalStatus.SystemDesignAssurance.ToString());
break;
case MessageFormat.AirbornePosition:
UpdateViewModelField(key, "BarometricAltitude", message.AirbornePosition.BarometricAltitude.ToString());
UpdateViewModelField(key, "Lattitude", message.AirbornePosition.CompactPosition.Latitude.ToString());
UpdateViewModelField(key, "Longitude", message.AirbornePosition.CompactPosition.Longitude.ToString());
break;
case MessageFormat.AircraftStatus:
if (message.AircraftStatus.EmergencyStatus.Squawk.HasValue)
{
UpdateViewModelField(key, "Squawk",
message.AircraftStatus.EmergencyStatus.Squawk.Value.ToString("0000"));
}
break;
}
}
/// <summary>
/// Creates a new object.
/// </summary>
/// <param name="utcNow"></param>
/// <param name="modeSMessage"></param>
/// <param name="adsbMessage"></param>
public ModeSMessageEventArgs(DateTime utcNow, ModeSMessage modeSMessage, AdsbMessage adsbMessage)
{
ReceivedUtc = utcNow;
ModeSMessage = modeSMessage;
AdsbMessage = adsbMessage;
}
public MainForm()
{
InitializeComponent();
_dataSet.Columns.Add("ICAO", typeof(string));
_dataSet.Columns.Add("LastUpdate", typeof(DateTime));
_dataSet.Columns.Add("Identification", typeof(string));
_dataSet.Columns.Add("Category", typeof(string));
_dataSet.Columns.Add("Squawk", typeof(string));
_dataSet.Columns.Add("AirborneVelocity", typeof(string));
_dataSet.Columns.Add("SIL", typeof(string));
_dataSet.Columns.Add("SDA", typeof(string));
_dataSet.Columns.Add("BarometricAltitude", typeof(string));
_dataSet.Columns.Add("Lattitude", typeof(string));
_dataSet.Columns.Add("Longitude", typeof(string));
dataGridView1.DataSource = _dataSet;
dataGridView1.Columns["LastUpdate"].DefaultCellStyle.Format = "dd/MM/yyyy HH:mm:ss";
dataGridView1.Columns["LastUpdate"].Width = 130;
var adsbTranslator = new AdsbTranslator();
adsbTranslator.Statistics = new Statistics();
Text = "ADSB# v" + Assembly.GetExecutingAssembly().GetName().Version;
_decoder.FrameReceived += delegate(byte[] frame, int length)
{
Interlocked.Increment(ref _frameCount);
var t = new ModeSTranslator();
t.Statistics = new Statistics();
var modeSMessage = t.Translate(frame, 0, null, false);
AdsbTranslator t2 = new AdsbTranslator();
t2.Statistics = new Statistics();
AdsbMessage adsbMessage = t2.Translate(modeSMessage);
if (adsbMessage != null)
{
BeginInvoke(new Action(delegate
{
Debug.Print(adsbMessage.ToString());
UpdateView(adsbMessage);
}));
}
};
confidenceNumericUpDown_ValueChanged(null, null);
timeoutNumericUpDown_ValueChanged(null, null);
try
{
_rtlDevice.Open();
var devices = DeviceDisplay.GetActiveDevices();
deviceComboBox.Items.Clear();
deviceComboBox.Items.AddRange(devices);
//_initialized = true;
deviceComboBox.SelectedIndex = 0;
deviceComboBox_SelectedIndexChanged(null, null);
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
/// <summary>
/// See interface docs.
/// </summary>
/// <param name="modeSMessage"></param>
/// <returns></returns>
public AdsbMessage Translate(ModeSMessage modeSMessage)
{
AdsbMessage result = null;
if (modeSMessage != null && modeSMessage.ExtendedSquitterMessage != null && modeSMessage.ExtendedSquitterMessage.Length == 7)
{
_BitStream.Initialise(modeSMessage.ExtendedSquitterMessage);
result = new AdsbMessage(modeSMessage);
result.Type = _BitStream.ReadByte(5);
switch (result.Type)
{
case 0: DecodeAirbornePosition(result); break;
case 1:
case 2:
case 3:
case 4: DecodeIdentification(result); break;
case 5:
case 6:
case 7:
case 8: DecodeSurfacePosition(result); break;
case 9:
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
case 16:
case 17:
case 18: DecodeAirbornePosition(result); break;
case 19: DecodeVelocity(result); break;
case 20:
case 21:
case 22: DecodeAirbornePosition(result); break;
case 28: DecodeAircraftStatus(result); break;
case 29: DecodeTargetStateAndStatus(result); break;
case 31: DecodeAircraftOperationalStatus(result); break;
}
if (_Statistics.Lock != null)
{
lock (_Statistics.Lock) {
++_Statistics.AdsbCount;
++_Statistics.AdsbMessageFormatCount[(int)result.MessageFormat];
++_Statistics.AdsbTypeCount[result.Type];
}
}
}
return(result);
}
/// <summary>
/// Returns true if the parent Mode-S message indicates that this is the payload from a coarse-format TIS-B message.
/// </summary>
/// <param name="message"></param>
/// <returns></returns>
private bool IsCoarseFormatTisb(AdsbMessage message)
{
return(message.ModeSMessage.DownlinkFormat == DownlinkFormat.ExtendedSquitterNonTransponder &&
message.ModeSMessage.ControlField == ControlField.CoarseFormatTisb);
}
/// <summary>
/// Decodes the content of aircraft operational status messages.
/// </summary>
/// <param name="message"></param>
private void DecodeAircraftOperationalStatus(AdsbMessage message)
{
message.MessageFormat = MessageFormat.AircraftOperationalStatus;
var subMessage = message.AircraftOperationalStatus = new AircraftOperationalStatusMessage();
var subType = _BitStream.ReadByte(3);
subMessage.AircraftOperationalStatusType = (AircraftOperationalStatusType)subType;
bool isSurfaceCapability = subMessage.AircraftOperationalStatusType == AircraftOperationalStatusType.SurfaceCapability;
var cc = _BitStream.ReadUInt16(isSurfaceCapability ? 12 : 16);
var len = isSurfaceCapability ? _BitStream.ReadByte(4) : (byte)0;
var om = _BitStream.ReadUInt16(16);
var version = subMessage.AdsbVersion = _BitStream.ReadByte(3);
if (version < 3 && subType < 2)
{
switch (subType)
{
case 0: subMessage.AirborneCapability = cc; break;
case 1:
if (version > 0)
{
subMessage.SurfaceCapability = (SurfaceCapability)cc;
if (version != 0 && (version != 2 || len != 0))
{
subMessage.MaximumLength = _MaximumLengths[len];
subMessage.MaximumWidth = _MaximumWidths[len];
}
}
break;
}
if (version > 0)
{
subMessage.OperationalMode = (OperationalMode)om;
if (version == 2)
{
subMessage.SystemDesignAssurance = (SystemDesignAssurance)((om & 0x300) >> 8);
if (subType == 1)
{
var gpsRight = (om & 0x80);
var gpsLat = (om & 0x60) >> 5;
var gpsLon = om & 0x1f;
if (gpsRight != 0 || gpsLat != 0)
{
subMessage.LateralAxisGpsOffset = (short)((gpsRight != 0 ? -1 : 1) * (gpsLat * 2));
}
if (gpsLon > 1)
{
subMessage.LongitudinalAxisGpsOffset = (byte)((gpsLon - 1) * 2);
}
}
}
subMessage.NicA = _BitStream.ReadBit() ? (byte)4 : (byte)0;
if (version == 2 && subType == 1)
{
subMessage.NicC = (byte)(om & 0x01);
}
subMessage.NacP = _BitStream.ReadByte(4);
if (version == 2 && subType == 0)
{
subMessage.Gva = _BitStream.ReadByte(2);
}
else
{
_BitStream.Skip(2);
}
subMessage.Sil = _BitStream.ReadByte(2);
if (subType == 0)
{
subMessage.NicBaro = _BitStream.ReadBit();
}
else
{
subMessage.SurfacePositionAngleIsTrack = _BitStream.ReadBit();
}
subMessage.HorizontalReferenceIsMagneticNorth = _BitStream.ReadBit();
if (version == 2)
{
subMessage.SilSupplement = _BitStream.ReadBit();
subMessage.IsRebroadcast = _BitStream.ReadBit();
}
}
}
}
/// <summary>
/// Decodes the target state and status message.
/// </summary>
/// <param name="message"></param>
private void DecodeTargetStateAndStatus(AdsbMessage message)
{
message.MessageFormat = MessageFormat.TargetStateAndStatus;
var subMessage = message.TargetStateAndStatus = new TargetStateAndStatusMessage();
subMessage.TargetStateAndStatusType = (TargetStateAndStatusType)_BitStream.ReadByte(2);
switch (subMessage.TargetStateAndStatusType)
{
case TargetStateAndStatusType.Version1:
var verticalDataSource = (VerticalDataSource)_BitStream.ReadByte(2);
var altitudeIsMeanSeaLevel = _BitStream.ReadBit();
if (!_BitStream.ReadBit()) // backwards compatibility bit - if this is non-zero then it's a version 0 TCP message that we need to ignore
{
var version1 = subMessage.Version1 = new TargetStateAndStatusVersion1();
version1.VerticalDataSource = verticalDataSource;
version1.AltitudesAreMeanSeaLevel = altitudeIsMeanSeaLevel;
version1.TargetAltitudeCapability = (TargetAltitudeCapability)_BitStream.ReadByte(2);
version1.VerticalModeIndicator = (VerticalModeIndicator)_BitStream.ReadByte(2);
var altitude = (int)_BitStream.ReadUInt16(10);
if (version1.VerticalDataSource != VerticalDataSource.None && altitude < 1011)
{
version1.TargetAltitude = (altitude * 100) - 1000;
}
version1.HorizontalDataSource = (HorizontalDataSource)_BitStream.ReadByte(2);
var heading = _BitStream.ReadUInt16(9);
if (version1.HorizontalDataSource != HorizontalDataSource.None && heading < 360)
{
version1.TargetHeading = (short)heading;
}
version1.TargetHeadingIsTrack = _BitStream.ReadBit();
version1.HorizontalModeIndicator = (HorizontalModeIndicator)_BitStream.ReadByte(2);
version1.NacP = _BitStream.ReadByte(4);
version1.NicBaro = _BitStream.ReadBit();
version1.Sil = _BitStream.ReadByte(2);
_BitStream.Skip(5);
version1.TcasCapabilityMode = (TcasCapabilityMode)_BitStream.ReadByte(2);
version1.EmergencyState = (EmergencyState)_BitStream.ReadByte(3);
}
break;
case TargetStateAndStatusType.Version2:
var version2 = message.TargetStateAndStatus.Version2 = new TargetStateAndStatusVersion2();
version2.SilSupplement = _BitStream.ReadBit();
version2.SelectedAltitudeIsFms = _BitStream.ReadBit();
var selAltitude = _BitStream.ReadUInt16(11);
if (selAltitude != 0)
{
version2.SelectedAltitude = (selAltitude - 1) * 32;
}
var pressure = _BitStream.ReadUInt16(9);
if (pressure != 0)
{
version2.BarometricPressureSetting = (((float)pressure - 1F) * 0.8F) + 800F;
}
bool headingIsValid = _BitStream.ReadBit();
var headingValue = _BitStream.ReadUInt16(9);
if (headingIsValid)
{
version2.SelectedHeading = (double)headingValue * 0.703125;
}
version2.NacP = _BitStream.ReadByte(4);
version2.NicBaro = _BitStream.ReadBit();
version2.Sil = _BitStream.ReadByte(2);
var autopilotValid = _BitStream.ReadBit();
version2.IsAutopilotEngaged = _BitStream.ReadBit();
version2.IsVnavEngaged = _BitStream.ReadBit();
version2.IsAltitudeHoldActive = _BitStream.ReadBit();
version2.IsRebroadcast = _BitStream.ReadBit();
version2.IsApproachModeActive = _BitStream.ReadBit();
version2.IsTcasOperational = _BitStream.ReadBit();
version2.IsLnavEngaged = _BitStream.ReadBit();
if (!autopilotValid)
{
version2.IsAutopilotEngaged = version2.IsVnavEngaged = version2.IsAltitudeHoldActive = version2.IsApproachModeActive = version2.IsLnavEngaged = null;
}
break;
}
}
/// <summary>
/// Decodes an aircraft status message.
/// </summary>
/// <param name="message"></param>
private void DecodeAircraftStatus(AdsbMessage message)
{
message.MessageFormat = MessageFormat.AircraftStatus;
var subMessage = message.AircraftStatus = new AircraftStatusMessage();
subMessage.AircraftStatusType = (AircraftStatusType)_BitStream.ReadByte(3);
switch (subMessage.AircraftStatusType)
{
case AircraftStatusType.EmergencyStatus:
var emergency = subMessage.EmergencyStatus = new EmergencyStatus();
emergency.EmergencyState = (EmergencyState)_BitStream.ReadByte(3);
var modeA = (short)_BitStream.ReadUInt16(13);
if (modeA != 0)
{
emergency.Squawk = ModeS.ModeATranslator.DecodeModeA(modeA);
}
break;
case AircraftStatusType.TcasResolutionAdvisoryBroadcast:
var tcas = subMessage.TcasResolutionAdvisory = new TcasResolutionAdvisory();
var araCoding = _BitStream.ReadBit();
var araValue = (short)_BitStream.ReadUInt16(13);
tcas.ResolutionAdvisoryComplement = (ResolutionAdvisoryComplement)_BitStream.ReadByte(4);
tcas.ResolutionAdvisoryTerminated = _BitStream.ReadBit();
tcas.MultipleThreatEncounter = _BitStream.ReadBit();
if (araCoding)
{
tcas.SingleThreatResolutionAdvisory = (SingleThreatResolutionAdvisory)araValue;
}
else if (tcas.MultipleThreatEncounter)
{
tcas.MultipleThreatResolutionAdvisory = (MultipleThreatResolutionAdvisory)araValue;
}
switch (_BitStream.ReadByte(2))
{
case 1:
tcas.ThreatIcao24 = (int)_BitStream.ReadUInt32(24);
break;
case 2:
var threatAltitude = _BitStream.ReadUInt16(13);
var threatRange = _BitStream.ReadByte(7);
var threatBearing = _BitStream.ReadByte(6);
var strippedAltitude = ((threatAltitude & 0x1F80) >> 2) | ((threatAltitude & 0x20) >> 1) | (threatAltitude & 0x0f);
tcas.ThreatAltitude = ModeSAltitudeConversion.LookupGillhamAltitude(strippedAltitude);
if (threatRange > 0)
{
tcas.ThreatRange = ((float)(threatRange - 1) / 10F) + 0.05F;
tcas.ThreatRangeExceeded = threatRange == 127;
}
if (threatBearing > 0 && threatBearing < 61)
{
tcas.ThreatBearing = (short)((threatBearing - 1) * 6);
}
break;
}
break;
}
}
/// <summary>
/// Decodes an airborne velocity message.
/// </summary>
/// <param name="message"></param>
private void DecodeVelocity(AdsbMessage message)
{
message.MessageFormat = MessageFormat.AirborneVelocity;
var subMessage = message.AirborneVelocity = new AirborneVelocityMessage();
var velocityType = _BitStream.ReadByte(3);
subMessage.VelocityType = (VelocityType)velocityType;
if (velocityType > 0 && velocityType < 5)
{
subMessage.ChangeOfIntent = _BitStream.ReadBit();
_BitStream.Skip(1);
switch (_BitStream.ReadByte(3))
{
case 0: subMessage.HorizontalVelocityError = 10F; break;
case 1: subMessage.HorizontalVelocityError = -10F; break;
case 2: subMessage.HorizontalVelocityError = -3F; break;
case 3: subMessage.HorizontalVelocityError = -1F; break;
case 4: subMessage.HorizontalVelocityError = -0.3F; break;
}
if (velocityType == 3 || velocityType == 4)
{
var headingAvailable = _BitStream.ReadBit();
var heading = _BitStream.ReadUInt16(10);
if (headingAvailable)
{
subMessage.Heading = (double)heading * 0.3515625;
}
subMessage.AirspeedIsTrueAirspeed = _BitStream.ReadBit();
var airspeed = _BitStream.ReadUInt16(10);
if (airspeed != 0)
{
if (airspeed == 1023)
{
subMessage.AirspeedExceeded = true;
}
subMessage.Airspeed = airspeed - 1;
if (velocityType == 4)
{
subMessage.Airspeed *= 4;
}
}
}
else
{
var vector = subMessage.VectorVelocity = new VectorVelocity()
{
IsWesterlyVelocity = _BitStream.ReadBit(),
EastWestVelocity = (short?)_BitStream.ReadUInt16(10),
IsSoutherlyVelocity = _BitStream.ReadBit(),
NorthSouthVelocity = (short?)_BitStream.ReadUInt16(10),
};
if (vector.EastWestVelocity == 0)
{
vector.EastWestVelocity = null;
}
else
{
vector.EastWestExceeded = vector.EastWestVelocity == 1023;
vector.EastWestVelocity = (short)((vector.EastWestVelocity - 1) * (velocityType == 1 ? 1 : 4));
}
if (vector.NorthSouthVelocity == 0)
{
vector.NorthSouthVelocity = null;
}
else
{
vector.NorthSouthExceeded = vector.NorthSouthVelocity == 1023;
vector.NorthSouthVelocity = (short)((vector.NorthSouthVelocity - 1) * (velocityType == 1 ? 1 : 4));
}
}
subMessage.VerticalRateIsBarometric = _BitStream.ReadBit();
var verticalRateSign = _BitStream.ReadBit() ? -1 : 1;
var verticalRate = _BitStream.ReadUInt16(9);
if (verticalRate != 0)
{
subMessage.VerticalRateExceeded = verticalRateSign == 511;
subMessage.VerticalRate = verticalRateSign * ((verticalRate - 1) * 64);
}
_BitStream.Skip(2);
var geometricDeltaSign = _BitStream.ReadBit() ? -1 : 1;
var geometricDelta = _BitStream.ReadByte(7);
if (geometricDelta != 0)
{
subMessage.GeometricAltitudeDeltaExceeded = geometricDelta == 127;
subMessage.GeometricAltitudeDelta = (short)(geometricDeltaSign * ((geometricDelta - 1) * 25));
}
}
}
/// <summary>
/// See interface docs.
/// </summary>
/// <param name="modeSMessage"></param>
/// <returns></returns>
public AdsbMessage Translate(ModeSMessage modeSMessage)
{
if (Statistics == null)
{
throw new InvalidOperationException("Statistics must be supplied before Translate can be called");
}
AdsbMessage result = null;
if (modeSMessage != null && modeSMessage.ExtendedSquitterMessage != null && modeSMessage.ExtendedSquitterMessage.Length == 7)
{
_BitStream.Initialise(modeSMessage.ExtendedSquitterMessage);
result = new AdsbMessage(modeSMessage);
result.ModeSMessage.Identity = modeSMessage.Identity;
if (IsCoarseFormatTisb(result))
{
DecodeCoarseTisbAirbornePosition(result);
}
else
{
result.Type = _BitStream.ReadByte(5);
switch (result.Type)
{
case 0: DecodeAirbornePosition(result); break;
case 1:
case 2:
case 3:
case 4: DecodeIdentification(result); break;
case 5:
case 6:
case 7:
case 8: DecodeSurfacePosition(result); break;
case 9:
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
case 16:
case 17:
case 18: DecodeAirbornePosition(result); break;
case 19: DecodeVelocity(result); break;
case 20:
case 21:
case 22: DecodeAirbornePosition(result); break;
case 28: DecodeAircraftStatus(result); break;
case 29: DecodeTargetStateAndStatus(result); break;
case 31: DecodeAircraftOperationalStatus(result); break;
}
}
if (Statistics != null)
{
Statistics.Lock(r => {
++r.AdsbCount;
++r.AdsbMessageFormatCount[(int)result.MessageFormat];
++r.AdsbTypeCount[result.Type];
});
}
}
else
{
result = new AdsbMessage(modeSMessage);
}
return(result);
}
