NAVIOR-24S
™
CHAPTER III
Software Interface
49
NAVIOR-24S ™
Revision
V1.00 20.05.2008
Timing Applications
The NAVIOR-24S GPS/GLONASS receiver is an excellent source for accurate system timing. Four
examples of applications requiring accurate time are environmental data acquisition and
synchronization of communications networks. The timing functions of the receiver are supported by
the BINR protocol and the PPS signal.
Note
– GPS time differs from UTC (Universal Coordinated Time), UTC SU (The Russian State
standard) and GLONASS time.
As of April 2002, the GPS UTC offset was 13 seconds. The offset increases by 1 second
approximately every 18 months. System designers should plan to read the offset value as a part of
the timing interface to obtain UTC. The GPS week number is in reference to a base week (Week
#0), starting January 6, 1980.
The current GPS UTC offset is contained within the almanac transmitted by the GPS system. The
NAVIOR-24S GPS/GLONASS receiver must have a complete almanac before the offset data is
valid.
Note
– As of January 2005, the GPS Control Organization has not added leap seconds on the usual
18 month schedule. As a result, the offset has remained at 13 seconds.
The scale of system time of GLONASS is updated simultaneously with planned correction into
integer number of seconds of UTC scale. The updating of UTC scale to
±
1 sec is realized by the
International Time Office on the recommendation of International Service. The updating of UTC
scale is usually realized with periodicity once in a year (once in one and a half year) at the end of
any quarter: at 00 hours 00 minutes 00 seconds in the midnight from the 31
st
of December to the 1
st
of January (or from the 31
st
of March to the 1
st
of April, from the 30
th
of June to the 1
st
of July, from
the 30
th
of September to the 1
st
of October). It is also realized simultaneously by all users who use
UTC scale.
The users are informed in time (no less than 3 months) about the moment and value of correction of
UTC scale with getting newsletters, notifications, etc. GLONASS satellites contain no data in
navigation messages about the correction of UTC scale.
As a result of periodic realization of planned second correction there is no shift of whole number of
seconds between system time of GLONASS and UTC (SU) scale.
However, there is a constant shift of whole number of hours between system time of GLONASS
and UTC (SU) scale, conditioned by operation features:
tGLONASS = UTC(SU) + 03 h 00 min
