private ArgosFix[] GetFixes(DateTime transmissionDateTime, ICollection<byte> message)
{
if (message == null)
return new ArgosFix[0];
//Get the message header
bool messageHasSensorData = message.BooleanAt(0);
//ignore sensor or error messages
if (messageHasSensorData)
return new ArgosFix[0];
if (message.Count < 9) //72 bits (9 bytes) required for a full absolute fix
return new[] { new ArgosFix { ConditionCode = ArgosConditionCode.Invalid } };
//Get the absolute Fix
byte reportedCrc = message.ByteAt(1, 6);
byte fixBufferType = message.ByteAt(7, 2);
uint longitudeBits = message.UInt32At(9, 22);
double longitude = longitudeBits.TwosComplement(22, 4);
uint latitudeBits = message.UInt32At(31, 21);
double latitude = latitudeBits.TwosComplement(21, 4);
ushort julian = message.UInt16At(52, 9);
byte hour = message.ByteAt(61, 5);
byte minute = message.ByteAt(66, 6);
DateTime fixDate = CalculateFixDate(transmissionDateTime, julian, hour, minute);
// Cyclical Redundancy Check
var crc = new Crc();
crc.Update(fixBufferType, 2);
crc.Update((int)longitudeBits, 22);
crc.Update((int)latitudeBits, 21);
crc.Update(julian, 9);
crc.Update(hour, 5);
crc.Update(minute, 6);
ArgosConditionCode cCode = crc.Value == reportedCrc ? ArgosConditionCode.Good : ArgosConditionCode.Bad;
var fixes = new List<ArgosFix>
{
new ArgosFix
{
ConditionCode = cCode,
Longitude = longitude,
Latitude = latitude,
DateTime = fixDate
}
};
//Setup for the relative fixes
if (fixBufferType > 3)
throw new InvalidDataException("Argos Message has invalid Fix Buffer Type.");
int numberOfRelativeFixes = new[] { 0, 3, 4, 5 }[fixBufferType];
int doubleLength = new[] { 0, 17, 12, 9 }[fixBufferType];
int relativeFixLength = new[] { 0, 46, 36, 30 }[fixBufferType];
//Get the relative fixes
for (var i = 0; i < numberOfRelativeFixes; i++)
{
int firstBit = 72 + i * relativeFixLength;
int bytesRequired = (firstBit + relativeFixLength + 7) / 8; //+7 to round up
if (message.Count < bytesRequired)
break;
reportedCrc = message.ByteAt(firstBit, 6);
firstBit += 6;
longitudeBits = message.UInt32At(firstBit, doubleLength);
double longitudeDelta = longitudeBits.TwosComplement(doubleLength, 4);
firstBit += doubleLength;
latitudeBits = message.UInt32At(firstBit, doubleLength);
double latitudeDelta = latitudeBits.TwosComplement(doubleLength, 4);
firstBit += doubleLength;
//Get the time of the relative fixes
byte delay = message.ByteAt(firstBit, 6);
TimeSpan timeOffset = TimeSpan.FromMinutes((i + 1) * Period.TotalMinutes);
fixDate = fixDate.AddMinutes(-fixDate.Minute); //Round down to the hour
// Cyclical Redundancy Check
crc = new Crc();
crc.Update((int)longitudeBits, doubleLength);
crc.Update((int)latitudeBits, doubleLength);
crc.Update(delay, 6);
cCode = crc.Value == reportedCrc ? ArgosConditionCode.Good : ArgosConditionCode.Bad;
//If the CRC is good we still need to check for values out of range
if (cCode == ArgosConditionCode.Good)
{
//if the 6 bits of delay are all ones the fix could not be acquired
if ((delay & 0x3F) == 0x3F)
cCode = ArgosConditionCode.Unavailable;
}
if (delay > 59) //59 min is max delay
delay = 0;
//NOTE: In some cases Unavailable is reported when CRC was bad, but usually not.
DateTime relFixDate;
if (fixDate == default(DateTime))
relFixDate = new DateTime(); // use default value
else
relFixDate = fixDate - timeOffset + TimeSpan.FromMinutes(delay);
fixes.Add(
new ArgosFix
{
ConditionCode = cCode,
Longitude = longitude + longitudeDelta,
Latitude = latitude + latitudeDelta,
DateTime = relFixDate
}
);
}
return fixes.ToArray();
}
private ArgosFix[] GetFixes(DateTime transmissionDateTime, ICollection <byte> message)
{
if (message == null)
{
return(new ArgosFix[0]);
}
//Get the message header
bool messageHasSensorData = message.BooleanAt(0);
//ignore sensor or error messages
if (messageHasSensorData)
{
return(new ArgosFix[0]);
}
if (message.Count < 9) //72 bits (9 bytes) required for a full absolute fix
{
return new[] { new ArgosFix {
ConditionCode = ArgosConditionCode.Invalid
} }
}
;
//Get the absolute Fix
byte reportedCrc = message.ByteAt(1, 6);
byte fixBufferType = message.ByteAt(7, 2);
uint longitudeBits = message.UInt32At(9, 22);
double longitude = longitudeBits.TwosComplement(22, 4);
uint latitudeBits = message.UInt32At(31, 21);
double latitude = latitudeBits.TwosComplement(21, 4);
ushort julian = message.UInt16At(52, 9);
byte hour = message.ByteAt(61, 5);
byte minute = message.ByteAt(66, 6);
DateTime fixDate = CalculateFixDate(transmissionDateTime, julian, hour, minute);
// Cyclical Redundancy Check
var crc = new Crc();
crc.Update(fixBufferType, 2);
crc.Update((int)longitudeBits, 22);
crc.Update((int)latitudeBits, 21);
crc.Update(julian, 9);
crc.Update(hour, 5);
crc.Update(minute, 6);
ArgosConditionCode cCode = crc.Value == reportedCrc ? ArgosConditionCode.Good : ArgosConditionCode.Bad;
var fixes = new List <ArgosFix>
{
new ArgosFix
{
ConditionCode = cCode,
Longitude = longitude,
Latitude = latitude,
DateTime = fixDate
}
};
//Setup for the relative fixes
if (fixBufferType > 3)
{
throw new InvalidDataException("Argos Message has invalid Fix Buffer Type.");
}
int numberOfRelativeFixes = new[] { 0, 3, 4, 5 }[fixBufferType];
int doubleLength = new[] { 0, 17, 12, 9 }[fixBufferType];
int relativeFixLength = new[] { 0, 46, 36, 30 }[fixBufferType];
//Get the relative fixes
for (var i = 0; i < numberOfRelativeFixes; i++)
{
int firstBit = 72 + i * relativeFixLength;
int bytesRequired = (firstBit + relativeFixLength + 7) / 8; //+7 to round up
if (message.Count < bytesRequired)
{
break;
}
reportedCrc = message.ByteAt(firstBit, 6);
firstBit += 6;
longitudeBits = message.UInt32At(firstBit, doubleLength);
double longitudeDelta = longitudeBits.TwosComplement(doubleLength, 4);
firstBit += doubleLength;
latitudeBits = message.UInt32At(firstBit, doubleLength);
double latitudeDelta = latitudeBits.TwosComplement(doubleLength, 4);
firstBit += doubleLength;
//Get the time of the relative fixes
byte delay = message.ByteAt(firstBit, 6);
TimeSpan timeOffset = TimeSpan.FromMinutes((i + 1) * Period.TotalMinutes);
fixDate = fixDate.AddMinutes(-fixDate.Minute); //Round down to the hour
// Cyclical Redundancy Check
crc = new Crc();
crc.Update((int)longitudeBits, doubleLength);
crc.Update((int)latitudeBits, doubleLength);
crc.Update(delay, 6);
cCode = crc.Value == reportedCrc ? ArgosConditionCode.Good : ArgosConditionCode.Bad;
//If the CRC is good we still need to check for values out of range
if (cCode == ArgosConditionCode.Good)
{
//if the 6 bits of delay are all ones the fix could not be acquired
if ((delay & 0x3F) == 0x3F)
{
cCode = ArgosConditionCode.Unavailable;
}
}
if (delay > 59) //59 min is max delay
{
delay = 0;
}
//NOTE: In some cases Unavailable is reported when CRC was bad, but usually not.
DateTime relFixDate;
if (fixDate == default(DateTime))
{
relFixDate = new DateTime(); // use default value
}
else
{
relFixDate = fixDate - timeOffset + TimeSpan.FromMinutes(delay);
}
fixes.Add(
new ArgosFix
{
ConditionCode = cCode,
Longitude = longitude + longitudeDelta,
Latitude = latitude + latitudeDelta,
DateTime = relFixDate
}
);
}
return(fixes.ToArray());
}