Channel
============================ channeldef.txt =================================
This file defines the columns of data in the channel.log file produced by the
GRID software receiver. Two types of measurement time stamps are given in
channel.log, both corresponding to the same event: the observables measurement
event:
(1) Raw Receiver Time (RRT): This time stamp is linked directly to the
receiver's sampling clock. It starts at zero when the receiver is
initialized and is never interrupted or adjusted by the code.
(2) Offset Receiver Time (ORT): This time stamp is equal to RRT plus an
offset that brings the result close (within a few ms) to true GPS
time:
ORT = RRT + tOffset
GRID automatically adjusts tOffset every so often to bring ORT within a few ms
of true GPS time. When tOffset is adjusted, a small jump in ORT is introduced
and concomitant shifts occur in the pseudorange and carrier phase data. For
maximum resolution, ORT is given in separate columns for week, whole second,
and fractional seconds.
=============================================================================
Column Quantity
1 ----------- RRT week number.
2 ----------- RRT seconds of week.
3 ----------- ORT week number.
4 ----------- ORT whole seconds of week.
5 ----------- ORT fractional second.
6 ----------- Apparent Doppler frequency in Hz (positive for approaching TXs).
7 ----------- Beat carrier phase in cycles (changes in the same sense as
pseudorange).
8 ----------- Pseudorange in meters.
9 ----------- Carrier-to-noise ratio (C/N0) in dB-Hz.
10 ---------- Flag indicating whether (1) or not (0) the pseudorange and
carrier phase measurements are valid.
11 ---------- A flag indicating whether (1) or not (0) an anomaly has been
detected in the PLL's phase tracking error. By anomaly is meant
a carrier cycle slip or unusually large phase error. Phase
measurements should be regarded with distrust if this flag is
asserted.
12 ---------- Channel status indicator:
0 STATUS_NULL
1 STATUS_ALLOCATED
2 STATUS_ACQUIRED
3 STATUS_SYMBOL_LOCK
4 STATUS_FREQ_LOCK
5 STATUS_PHASE_LOCK
6 STATUS_DATA_LOCK
13 ---------- Signal type:
0 GPS_L1_CA // GPS L1 legacy civil code
1 GPS_L2_CM // GPS L2 civil M code
2 GPS_L2_CL // GPS L2 civil L code
3 GPS_L2_CLM // GPS L2 M+L combined tracking
4 GPS_L5_I // GPS L5 civil in-phase
5 GPS_L5_Q // GPS L5 civil quadrature
6 GPS_L5_IQ // GPS L5 civil I+Q combined tracking
7 GPS_L1_CA_ALT1 // GPS L1 C/A for alternative L1C bank
8 CDMA_UHF_PILOT // Cellular CDMA pilot, I+Q signal
9 CDMA_UHF_SYNC // Cellular CDMA pilot+sync, I+Q signal
14 ---------- Transmitter identification number (TXID).
=============================================================================