ZED-F9R-Integration manual
Important: Users are recommended to check the gnssFixOK flag in the UBX-NAV-PVT or
the NMEA valid flag. Fixes not marked valid should not be used.
UBX-NAV-STATUS message also reports whether a fix is valid in the gpsFixOK flag. This message
has only been retained for backwards compatibility and users are recommended to use the UBX-
NAV-PVT message.
3.1.10.4 Weak signal compensation
In normal operating conditions, low signal strength (i.e. signal attenuation) indicates likely
contamination by multi-path. The receiver trusts such signals less in order to preserve the quality of
the position solution in poor signal environments. This feature can result in degraded performance
in situations where the signals are attenuated for another reason, for example due to antenna
placement. In this case, the weak signal compensation feature can be used to restore normal
performance. There are three possible modes:
• Disabled: no weak signal compensation is performed
• Automatic: the receiver automatically estimates and compensates for the weak signal
• Configured: the receiver compensates for the weak signal based on a configured value
These modes can be selected using CFG-NAVSPG-SIGATTCOMP. In the case of the "configured"
mode, the user should input the maximum C/N0 observed in a clear-sky environment, excluding
any outliers or unusually high values. The configured value can have a large impact on the receiver
performance, so it should be chosen carefully.
3.2 High precision sensor fusion (HPS)
3.2.1 Introduction
u-blox solutions for high precision sensor fusion (HPS) allow high-accuracy positioning in places
with poor or no GNSS coverage. HPS is based on sensor fusion dead reckoning (SFDR) technology,
which combines GNSS measurements with those from external sensors. The ZED-F9R computes
a solution type called GAWT (gyroscope, accelerometers, wheel tick) by combining GNSS
measurements with the outputs of a 3-axis accelerometer, a 3-axis gyroscope and wheel tick
(sometimes called a speed tick) or speed measurements. The utilization of these sensors ensures
a quick recovery of the navigation solution after short GNSS signal outage (going under a bridge,
signaling panels, and so on).
The firmware automatically detects and continuously calibrates the sensors.
3.2.2 HPS dynamic platform models
ZED-F9R supports different dynamic platform models to adjust the high precision sensor fusion
navigation engine to the expected application environment. These platform settings can be
changed dynamically without performing a power cycle or reset. However, it requires a recalibration
of the sensors (IMU + WT/speed measurements). The settings improve the receiver's interpretation
of the measurements and thus provide a more accurate position output. Setting the receiver to an
unsuitable platform model for the given application environment is likely to result in a loss of receiver
performance and position accuracy.
The dynamic platform model can be configured through the CFG-NAVSPG-DYNMODEL configuration
item.
ZED-F9R's high precision sensor fusion algorithm is optimized for the following platforms.
• Automotive
UBX-20039643 - R06
3 Receiver functionality Page 20 of 119
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