IMU covariance using Euler packet#14
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4lon wants to merge 2 commits intoadvanced-navigation:masterfrom
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IMU covariance using Euler packet#144lon wants to merge 2 commits intoadvanced-navigation:masterfrom
4lon wants to merge 2 commits intoadvanced-navigation:masterfrom
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May 7, 2025 13:41
Original decoder used quaternion standard deviation elements Q0, Q1, and Q2 directly as covariances around the x, y, and z axes in the IMU message. This doesn't seem like a valid way to interpret these values. Euler standard deviation converted into covariance has replaced this to give better values in the IMU message covariance matrix.
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The driver was using 3 out of 4 quaternion standard deviation values and populating the ROS2 IMU message orientation covariance matrix with them.
This covariance matrix is intended to be row major about the x, y, and z axes as detailed here:
https://docs.ros2.org/foxy/api/sensor_msgs/msg/Imu.html
As such, I'm not sure it is valid to populate this matrix with standard deviation values from a quaternion. I think a more representative value can be obtained by using ANPP 26, euler standard deviation, and converting it to covariance.
I have replaced the ANPP 27 decoder instead of adding the ANPP 26 decoder because ANPP 27 doesn't seem as usable for the message types included in this driver.