Time Definitions - Novatel OEM6 Series User Manual

Chapter 4
4.6.2

Time Definitions

The following are related definitions:
Coarse Time
Fine Time
Fine Clock
Cold Clock
Warm Clock
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The OEM6 Family Firmware Reference Manual
mentioned above.
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Each subframe contains the transmit time of the next subframe in seconds of GPS
Time of Week (TOW). After the first subframe is collected and decoded by the
receiver, an approximate calculation of the receiver clock offset can be made. The
receiver clock offset is the difference between GPS time and internal receiver time.
The calculation is based on subframe transmit time and the approximate propagation
time from the satellite signal to the receiver. The position of the satellite and receiver
clock offset are used to re-initialize the seconds counter on the receiver, resulting in
receiver/GPS time synchronization. The accuracy of the receiver time is expected to
be within 30 milliseconds (ms) of GPS time. This initial synchronization is referred to
as coarse time and is indicated by COARSE in the time status field of the TIMESYNC
log.
When at least four satellites are acquired to calculate the antenna position, a more
accurate estimate of the receiver clock offset is calculated. The new receiver clock
offset is used to synchronize the receiver clock even closer to GPS time. This is
referred to as fine time and appears as FINE or FINESTEERING in the time status
field of the TIMESYNC log. Fine time accuracy is a function of the GPS constellation
status. For the Standard Position Service (SPS) the time accuracy is specified as 300
ns (1 sigma), assuming that clock steering is enabled.
An OEM6 family receiver tracking satellites and has a FINE or FINESTEERING
receiver clock state.
An OEM6 family receiver that needs to have its clock synchronized with the Fine
receiver. It may have any clock state (except FINE or FINESTEERING) that includes
UNKNOWN.
An OEM6 family receiver that has its clock adjusted to greater than 500 ms. Refer to
the TIME log to view the clock offset.
Operation OEM6 Cards and Enclosure
(OM-20000129) contains details of the logs
OEM6 Family Installation and Operation User Manual Rev 7