NEO-M9N - Integration manual
3.2 SBAS
NEO-M9N 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 NEO-M9N 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
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 Ranging and Integrity Monitoring Stations (RIMS) are combined to
make a Total Electron Content (TEC) map. This map is transferred to the receiver via SBAS satellites
to allow a correction of the ionosphere error on each received signal.
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
9
Satellite navigation (ephemeris)
All
10
Degradation
Primary
12
Time offset
Primary
17
Satellite almanac
All
18
Ionosphere grid point assignment
Primary
24
Mixed fast / long-term corrections
Primary
25
Long-term corrections
Primary
26
Ionosphere delays
Primary
Table 6: Supported SBAS messages
Each satellite services a specific region and its correction signal is only useful within that region.
Planning is crucial to determine the best possible configuration, especially in areas where signals
from different SBAS systems can be received:
•
Example 1 - SBAS receiver in North America:
In the eastern parts of North America, make sure
that EGNOS satellites do not take preference over WAAS satellites. The satellite signals from
the EGNOS system should be disallowed by using the PRN mask.
•
Example 2 - SBAS receiver in Europe:
Some WAAS satellite signals can be received in the
western parts of Europe, therefore it is recommended that the satellites from all but the
EGNOS system should be disallowed using the PRN mask.
Although u-blox receivers try to select the best available SBAS correction data, it is
recommended to configure them to exclude unwanted SBAS satellites.
UBX-19014286 - R07
3 Receiver functionality
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