Novatel MiLLennium OM-20000040 User Manual page 91

H.1.3 GCLA/B CLOCK INFORMATION
This log contains the time difference information between GPS and GLONASS time as well as status flags. The
status flags are used to indicate the type of time processing used in the least squares adjustment. GPS and
GLONASS time are both based on the Universal Time Coordinated (UTC) time scale with some adjustments. GPS
time is continuous and does not include any of the leap second adjustments to UTC applied since 1980. The result
is that GPS time currently leads UTC time by 13 seconds.
GLONASS time applies leap seconds but is also three hours ahead to represent Moscow time. The nominal offset
between GPS and GLONASS time is therefore due to the three hour offset minus the leap second offset. Currently
this value is at 10787 seconds with GLONASS leading. As well as the nominal offset, there is a residual offset on
the order of nanoseconds which must be estimated in the least squares adjustment. The GLONASS-M satellites
will broadcast this difference in the navigation message.
This log will also contain information from the GLONASS navigation data relating GLONASS time to UTC.
GCLA
Structure:
$GCLA week sec
τ
A # GPS sv
N
c
Field # Field
1 $GCLA
2 Week
3 Sec
4 Nominal Offset
5 Residual Offset
6 Residual Offset
Variance
7 A
N
τ
8
c
9 # GPS sv
10 # GLONASS sv
11 Time Status
12 * xx
13 [CR][LF]
Example:
$GCLA,994,149871.00,10787,10.62179349,167.82950123,1121,
-3.0544738044739E-007,9,4,00000000*7B,[CR][LF]GCLB
GPS/GLONASS Receiver User Manual Rev 1
nominal offset
# GLONASS sv
Description
Log Header
GPS week number
GPS time into week
Nominal offset between GPS and GLONASS time references,
in seconds
Residual offset estimated in filter, in meters
Variance of residual offset, in meters
Calendar day number within four year period beginning since
the leap year, in days
From GLONASS almanac - GLONASS time scale correction
to UTC(SU) given at beginning of day N
Number of good GPS sv tracked
Number of good GLONASS sv tracked
see
Time status ( below)
Checksum
Sentence terminator
Time Status
Value
0 GLONASS time floating
1 GLONASS time fixed
H NovAtel Format Logs
residual offset residual offset variance
time status *xx
A
, in seconds
Description
[CR][LF]
Example
$GCLA
994
149871.00
10787
10.62179349
167.82950123
1121
-3.0544738044739E-007
9
4
00000000
*7B
[CR][LF]
91