public IGPSSatelliteVehicle[] GetSatelliteData()
{
GPSSatDataType[] iQueSatData = new GPSSatDataType[maxSatellites];
ushort err = GPSGetSatellites(iQueSatData);
if (err == 0)
{
// Work out how many satellites are in view.
int numSatellitesInView = 0;
for (int i = 0; i < maxSatellites; i++)
{
if (iQueSatData[i].svid != 255)
{
numSatellitesInView++;
}
}
// Construct the satellite data class.
IGPSSatelliteVehicle[] satelliteVehicles = new IGPSSatelliteVehicle[numSatellitesInView];
int index = 0;
for (int i = 0; i < maxSatellites; i++)
{
if (iQueSatData[i].svid != 255)
{
GPSSatelliteVehicle vehicle = new GPSSatelliteVehicle();
vehicle.PRN = iQueSatData[i].svid;
vehicle.AziumthDegrees = (int)Math.Round(iQueSatData[i].azimuth * 180 / Math.PI);
vehicle.ElevationDegrees = (int)Math.Round(iQueSatData[i].elevation * 180 / Math.PI);
vehicle.SNRdB = iQueSatData[i].snr / 100;
vehicle.HaveEphemerisData = (iQueSatData[i].status & gpsSatEphMask) > 0;
vehicle.HaveDifferentialCorrection = (iQueSatData[i].status & gpsSatDifMask) > 0;
vehicle.UsedInFix = (iQueSatData[i].status & gpsSatUsedMask) > 0;
vehicle.IsRising = (iQueSatData[i].status & gpsSatRisingMask) > 0;
satelliteVehicles[index++] = vehicle;
}
}
// Return the result.
return(satelliteVehicles);
}
else
{
return(null);
}
}
private void ProcessGSV(string[] parts)
{
// Check that we have the correct number of parts.
int numMessages, messageNumber, numSatellitesInView, numSatellitesInSentence;
if (parts.Length < 4)
{
CallOnLogEvent("Invalid GSV sentence.");
return;
}
try
{
numMessages = int.Parse(parts[1]);
messageNumber = int.Parse(parts[2]);
numSatellitesInView = int.Parse(parts[3]);
numSatellitesInSentence = messageNumber < numMessages ?
4 : numSatellitesInView - 4 * (numMessages - 1);
}
catch
{
CallOnLogEvent("Invalid GSV sentence.");
return;
}
// Need to allow for cases where the exact number of satellites are present,
// and where placeholder commas are used to pad missing satellite data in the
// last sentence.
if ((parts.Length != numSatellitesInSentence * 4 + 4) && (parts.Length != 20))
{
CallOnLogEvent("Invalid GSV sentence.");
return;
}
// Create a new satellite data instance if this is the first record.
if (messageNumber == 1)
{
partialSatelliteVehicles = new GPSSatelliteVehicle[numSatellitesInView];
partialSatelliteVehicleIndex = 0;
}
// Check that the message isn't out of sequence.
if (messageNumber != lastGSVMessageNumber + 1)
{
partialSatelliteVehicles = null;
partialSatelliteVehicleIndex = 0;
}
if (messageNumber == numMessages)
{
lastGSVMessageNumber = 0;
}
else
{
lastGSVMessageNumber = messageNumber;
}
// Sanity check.
if ((partialSatelliteVehicles != null) &&
(numSatellitesInView != partialSatelliteVehicles.Length))
{
partialSatelliteVehicles = null;
partialSatelliteVehicleIndex = 0;
}
// Check if we have a satellite data instance in case we didn't see the
// first record or we invalidated the satellite data above.
if (partialSatelliteVehicles != null)
{
// Add the satellite data to the list, if there is space.
for (int i = 0; i < numSatellitesInSentence; i++)
{
// Sanity check.
if (partialSatelliteVehicleIndex >= numSatellitesInView)
{
throw new Exception("Too many satellite vehicles in GSV sentence.");
}
// Create a new vehicle entry.
GPSSatelliteVehicle vehicle = new GPSSatelliteVehicle();
partialSatelliteVehicles[partialSatelliteVehicleIndex++] = vehicle;
// Populate the entry.
try
{
int partOffset = i * 4 + 4;
vehicle.PRN = int.Parse(parts[partOffset]);
vehicle.ElevationDegrees = parts[partOffset + 1].Equals(String.Empty) ? 0 : int.Parse(parts[partOffset + 1]);
vehicle.AziumthDegrees = parts[partOffset + 2].Equals(String.Empty) ? 0 : int.Parse(parts[partOffset + 2]);
vehicle.SNRdB = parts[partOffset + 3].Equals(String.Empty) ? 0 : int.Parse(parts[partOffset + 3]);
vehicle.HaveEphemerisData = true; // Assumed.
}
catch
{
throw new Exception("Invalid satellite vehicle data in GSV sentence.");
}
}
// If this is the last message then publish the data.
if (messageNumber == numMessages)
{
// Flag which satellites are used in the fix if this information is
// available.
if ((gsaData != null) && (DateTime.Now.Subtract(gsaData.timeReceived).TotalSeconds < gsaDataValiditySeconds))
{
for (int i = 0; i < gsaData.satellitesInFix.Length; i++)
{
for (int j = 0; j < partialSatelliteVehicleIndex; j++)
{
if (gsaData.satellitesInFix[i] == partialSatelliteVehicles[j].PRN)
{
partialSatelliteVehicles[j].UsedInFix = true;
break;
}
}
}
}
// Sort the vehicles in order of PRN.
Array.Sort(partialSatelliteVehicles);
// Publish the data.
m_MostRecentSatelliteVehicles = partialSatelliteVehicles;
// Tidy up.
partialSatelliteVehicles = null;
partialSatelliteVehicleIndex = 0;
}
}
}
