Chapter 3 OEM7 Receiver Operation
OEM7 Installation and Operation User Manual v1 56
RTK ASSIST is available as soon as the rover receiver has at least one valid RTK solution and
has received the RTK ASSIST correction data. If an RTK correction outage occurs, then RTK
ASSIST will maintain RTK mode until the subscription-permitted RTK ASSIST duration is
exceeded. A shorter, user-defined RTK ASSIST time out can also be set using the
RTKASSISTTIMEOUT command. Normal RTK operation will seamlessly resume if RTK cor-
rections are restored at any point while RTK ASSIST is operating.
RTK ASSIST will report the RTK solution type that was present before RTK corrections were lost,
unless the estimated solution standard deviation exceeds the threshold set by the
RTKINTEGERCRITERIA command. If this occurs, then integer RTK solutions will be down-
graded to their float RTK equivalent.
RTK ASSIST is enabled by default, but can be disabled using the RTKASSIST command. To mon-
itor the status of RTK ASSIST, view the RTKASSISTSTATUS log.
Refer to the OEM7 Commands and Logs Reference Manual (OM-20000169) for information about
the commands and logs referenced in this section.
RTK ASSIST typically provides 4 cm accuracy. However, if the RTK outage occurs during
the first 30 minutes of receiver operation, the position accuracy provided by RTK ASSIST
may be lower.
3.11 Transferring Time Between Receivers
The ADJUST1PPS command is used as part of the procedure to transfer time between receiv-
ers. The number of Pulses Per Second (PPS) is always set to 1 with this command. It is typically
used when the receiver is not adjusting its own clock and is using an external reference fre-
quency.
The TIMESYNC log is also used to synchronize time between receivers. It contains a time
status field that may show COARSE or FINE, among others. For a complete list of the time status
values and definitions, refer to the GPS Time Status section in Chapter 1 of the OEM7 Commands
and Logs Reference Manual (OM-20000169).
Procedures to Transfer Time on the next page provides details on the time transfer procedure.
Terms used in the procedure are defined in Time Definitions below. Refer also to the
ADJUST1PPS command and the TIMESYNC log descriptions in the OEM7 Commands and Logs
Reference Manual (OM-20000169).
3.11.1 GPS to Receiver Time Synchronization
Receiver time synchronization with GPS time does not occur until the receiver locks onto the
first satellite. The GPS L1 signal has two main streams of data modulated on the carrier. These
data streams are the C/A code (1.023 MHz rate) and the P(Y) code (10.23 MHz rate). Addi-
tionally, a navigation message (at a 50 Hz rate) contains GPS satellite data including the eph-
emeris, clock corrections and constellation status. This navigation message is encoded on both
the C/A and P(Y) codes. The navigation message is transmitted via individual subframes and
each subframe is 300 bits in length. With the 50 Hz data bit rate there is a new subframe trans-
mitted every six seconds.
3.11.2 Time Definitions
The following are related definitions:
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