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D Logs summary
MiLLennium Command Descriptions Manual 131
CLKA/B Receiver Clock Offset Data
This record is used to monitor the state of the receiver time. Its value will depend on the CLOCKADJUST command.
If
CLOCKADJUST is enabled, then the offset and drift times will approach zero. If not enabled, then the offset will
grow at the oscillator drift rate. Disabling
CLOCKADJUST and monitoring the CLKA/B log will allow you to
determine the error in your GPSCard receiver reference oscillator as compared to the
GPS satellite reference.
All logs report
GPS time not corrected for local receiver clock error. To derive the closest GPS time one must
subtract the clock offset shown in the
CLKA log (field 4) from GPS time reported.
The internal units of the new clock model’s three states (offset, drift and GM state) are meters, meters per second,
and meters. When scaled to time units for the output log, these become seconds, seconds per second, and seconds,
respectively. Note that the old units of the third clock state (drift rate) are seconds per second per second.
CLKA
Structure:
Example
$CLKA,841,499296.00,9.521895494E-008,-2.69065747E-008,2.061788299E-006,
9.642598169E-008,8.685638908E-010,0*4F
$CLKA week seconds
offset
drift SA G-M state offset std
drift std cm status *xx [CR][LF]
Field # Field type Data Description Example
1 $CLKA Log header $CLKA
2 week GPS week number 637
3 seconds GPS seconds into the week 511323.00
4 offset Receiver clock offset, in seconds. A positive offset implies that the
receiver clock is ahead of GPS Time. To derive GPS time, use the
following formula: GPS time = receiver time - (offset)
-4.628358547E-003
5 drift Receiver clock drift, in seconds per second. A positive drift implies that
the receiver clock is running faster than GPS Time.
-2.239751396E-007
6 SA G-M state This field contains the output value of the Gauss-Markov Selective
Availability clock dither estimator, in units of seconds. The value reflects
both the collective SA-induced short-term drift of the satellite clocks as
well as any range bias discontinuities that would normally affect the clock
model’s offset and drift states.
2.061788299E-006
7 offset std Standard deviation of receiver clock offset, in seconds 5.369997167E-008
8 drift std Standard deviation of receiver drift, in seconds per second 4.449097711E-009
9 cm status Receiver Clock Model Status where 0 is valid and values from -20 to -1
imply that the model is in the process of stabilization
0
10 *xx Checksum *7F
11 [CR][LF] Sentence terminator [CR][LF]