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to enable SBAS integrity on borders of SBAS service regions in order not to inadvertently
restrict the number of available signals.
SBAS integrity information is required for at least 5 GPS satellites. If this condition is not
met, SBAS integrity data will not be applied.
SBAS is only used if no correction services are available. If the connection stream is lost
during the operation, the receiver will switch to using the SBAS corrections after the time
set in CFG-NAVSPG-CONSTR_DGNSSTO (60 s by default) has elapsed.
When the receiver switches from a solution using correction data to a standard position
solution, the reference frame of the output position will switch from the one of the
correction data to that of the standard position solution. For an SBAS solution this
reference frame will be aligned within a few cm of WGS84 (and modern ITRF realizations).
3.3 Geofencing
3.3.1 Introduction
Figure 5: Geofence
The geofencing feature allows for the configuration of up to four circular areas (geofences) on the
Earth's surface. The receiver will then evaluate for each of these areas whether the current position
lies within the area or not and signal the state via UBX messaging and PIO toggling.
3.3.2 Interface
Geofencing can be configured using the CFG-GEOFENCE-* configuration group. The geofence
evaluation is active whenever there is at least one geofence configured.
The current state of each geofence plus the combined state is output in UBX-NAV-GEOFENCE with
every navigation epoch.
3.3.3 Geofence state evaluation
With every navigation epoch the receiver will evaluate the current solution's position versus the
configured geofences. There are three possible outcomes for each geofence:
• Inside - The position is inside the geofence with the configured confidence level
• Outside - The position lies outside of the geofence with the configured confidence level
• Unknown - There is no valid position solution or the position uncertainty does not allow for
unambiguous state evaluation
The position solution uncertainty (standard deviation) is multiplied with the configured confidence
sigma level and taken into account when evaluating the geofence state (red circle in
UBX-22004121 - R01
C1-Public
3 Receiver functionality
Early production information
RCB-F9T - Integration manual
Figure
6).
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