ZED-F9R-Integration manual
The positioning performance is not guaranteed in special maneuvers where the lawn mower
is lifted, carried or flipped 180 degrees.
3.2.3 Solution type
ZED-F9R produces a solution that combines GNSS signals with data from gyroscopes,
accelerometers and wheel tick sensors to compute a fused navigation solution. The solution type is
called GAWT, and it is described in the following sections.
To operate the ZED-F9R in GAWT mode with optimal performance, the following tasks need to be
completed:
• The IMU misalignment angles are also essential. It is recommended to enable automatic
alignment with the CFG-SFIMU-AUTO_MNTALG_ENA key, if misalignment angles are unknown.
The misalignment angles can also be configured manually with CFG-SFIMU-IMU_MNTALG
keys. Configuring misalignment angles manually speeds up the calibration procedure.
• It is mandatory to perform an initial calibration drive after flashing software, a cold start,
or changing sensor configuration keys (CFG-SFCORE-*, CFG-SFIMU-* or CFG-SFODO-*).
The calibration drive allows the software to detect and calibrate the sensors. See section
Accelerated Initialization and Calibration Procedure for additional information. Performance is
likely to be sub-optimal if the calibration drive is not performed correctly.
• If the maximum counter value of a wheel tick sensor cannot be represented as a power of 2
value, it must be configured manually. See section Odometer Types for additional information.
• It is strongly recommended that RTCM stream is available during the initial calibration drive, so
that the resulting calibration parameters can be estimated more accurately.
3.2.4 Installation configuration
If the GNSS antenna is placed at a significant distance from the receiver, position offsets
can be introduced which might affect the accuracy of the navigation solution. In order to
compensate for the position offset advanced configurations can be applied. Contact u-blox
support for more information on advanced configurations.
3.2.4.1 IMU-mount alignment
This section describes how IMU-mount misalignment angles, that is, the angles which rotate the
installation frame to the IMU-frame, can be configured.
The IMU-mount misalignment angles are defined as follows:
• The transformation from the installation frame to the IMU frame is described by three Euler
angles about the installation frame axes denoted as IMU-mount roll, IMU-mount pitch and IMU-
mount yaw angles. All three angles are referred to as the IMU-mount misalignment angles.
The default assumption is that the IMU-frame and the installation frame have the same orientation
(that is, all axes are parallel). If the IMU-mount misalignment angles are slightly incorrect (typically a
few degrees), the navigation solution can be degraded. If there are large (tens of degrees) IMU-mount
misalignments, the position calculation may fail. Therefore, it is essential to correctly configure the
IMU-mount misalignment settings.
It is strongly recommended to use the automatic IMU-mount alignment as described in the
following section.
3.2.4.1.1 Automatic IMU-mount alignment
The automatic IMU-mount alignment engine automatically estimates the IMU-mount roll, pitch and
yaw angles. It requires an initialization phase during which no INS/GNSS fusion can be achieved
(see the Fusion filter modes section for further details). The progress of the automatic alignment
initialization can be monitored with the UBX-ESF-STATUS message, and/or with the UBX-ESF-ALG
UBX-20039643 - R06
3 Receiver functionality Page 23 of 119
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