FixPosition Vision-RTK 2 - IMU Calibration

There are three recording levels available:
• Minimal:
• Time and system information.
• Fusion engine status, information, and output.
• User I/O.
• External sensors (wheel odometry).
• Internal sensors (processed GNSS, IMU).
• ROS information (clock, TF).
• Medium:
• Same as minimal.
• Raw GNSS and NTRIP data, latency, and status.
• Maximal:
• Same as medium.
• Camera image.
5.10. IMU calibration
The Vision-RTK 2 requires a start-up procedure before being fully operational. The user
must ensure the following requirements are fulfilled to start the calibration procedure:
• Both receivers have an RTK-fixed status.
• The Fusion engine is initialized, and the extrinsics are correct.
Once fulfilled, drive approximately 2 minutes under RTK-fixed with some dynamic move-
ment to converge the IMU biases. Perform eight figures and move back-and-forth within
a 10 meters area as shown in Figure 5.25. The gyroscope and accelerometer bias will
converge to steady values with this procedure. The sensor will raise a flag once it is fully
calibrated (see #N
o
22 in FP A-ODOMETRY described in Subsection 7.3.1).
On the web interface, the user can visualize the status of the calibration procedure and the
IMU noise by heading to the bottom of the "Status → Fusion" page. The corresponding
indicators are presented in Figure 5.24. The IMU bias estimation can be either Unknown
(sensor not initialized), Not converged, or Converged. Similarly, the IMU signal quality
indicators can be either Unknown, Low IMU noise, Medium IMU noise, or Excessive
IMU noise. Keep in mind that this indicator is calculated based on the variance of the
IMU measurements over a period of time. Some platforms might experience excessive
IMU noise without a significant impact on performance. This indicator only informs the
user of their system dynamics.
IMU bias estimation
Unknown Not converged Converged
IMU signal quality
Unknown Excessive IMU noise Medium IMU noise Low IMU noise
Figure 5.24.: IMU bias estimation and signal quality indicators
Vision-RTK 2 | Fixposition Positioning Sensor 39