ZED-F9P - Integration manual
Figure 8: Flowchart of the course over ground freezing
3.2 SBAS
ZED-F9P high precision receiver 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 ZED-F9P high precision receiver 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/or 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
(Testmode 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 ZED-F9P
Interface description [
]). The message UBX-NAV-SBAS provides detailed information about which
corrections are available and applied.
The most important SBAS feature for accuracy improvement is Ionosphere correction. The
measured data from regional RIMS stations are combined to make a TEC (Total Electron Content)
Map. This map is transferred to the receiver via the satellites to allow a correction of the ionosphere
error on each received satellite.
Message type
Message content
Source
0(0/2)
Test mode
All
1
PRN mask assignment
Primary
2, 3, 4, 5
Fast corrections
Primary
6
Integrity
Primary
7
Fast correction degradation
Primary
UBX-18010802 - R08
3 Receiver functionality
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Early production information
