Ublox RCB-F9T, Руководство по интеграции

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RCB-F9T - Integration manual
3.1.8.5 Freezing the course over ground
If the low-speed course over ground filter is deactivated or inactive (see section Low-speed course
over ground filter ), the receiver derives the course over ground from the GNSS velocity information.
If the velocity cannot be calculated with sufficient accuracy (e.g., with bad signals) or if the absolute
speed value is very low (under 0.1 m/s) then the course over ground value becomes inaccurate too.
In this case the course over ground value is frozen, i.e. the previous value is kept and its accuracy
is degraded over time. These frozen values will not be output in the NMEA messages NMEA-RMC
and NMEA-VTG unless the NMEA protocol is explicitly configured to do so (see NMEA protocol
configuration in the applicable interface description [
2 ]).
Figure 4: Flowchart of the course over ground freezing
3.2 SBAS
Whilst the RCB-F9T can make use of SBAS satellites, experience has shown that employing these
signals can degrade the timing performance and hence SBAS use is not enabled by default. The
following section describes the receiver operation when SBAS reception is required by users.
The RCB-F9T is capable of receiving multiple SBAS signals concurrently, even from different SBAS
systems (WAAS, EGNOS, MSAS, etc.). They can be tracked and used for navigation simultaneously.
Every SBAS satellite that broadcasts ephemeris or almanac information can be used for navigation,
just like a normal GNSS satellite.
For receiving correction data, the RCB-F9T automatically chooses the best SBAS satellite as its
primary source. It will select only one since the information received from other SBAS satellites is
redundant and could be inconsistent. The selection strategy is determined by the proximity of the
satellites, the services offered by the satellite, the configuration of the receiver (test mode allowed/
disallowed, integrity enabled/disabled) and the signal link quality to the satellite.
If corrections are available from the chosen SBAS satellite and used in the navigation calculation, the
differential status will be indicated in several output messages such as UBX-NAV-PVT, UBX-NAV-
STATUS, UBX-NAV-SAT, NMEA-GGA, NMEA-GLL, NMEA-RMC and NMEA-GNS (see the applicable
UBX-22004121 - R01 3 Receiver functionality Page 19 of 64
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