question about the sensor measurement of kinematic example

[yuan0623]

Hi, I'm trying to reproduce your results on my own to make sure that I really understand your paper Contact-Aided Invariant Extended Kalman Filtering for Robot State Estimation*. When I look into the KINEMATIC measurement in imu_kinematic_measurements.txt, I find it is quite strange.
Here is my understanding: instead of measuring the joint encoder of the Cassie, the imu_kinematic_measurements.txt provides the relative position between the foot and the robot directly, which I can understand. However, The imu_kinematic_measurements.txt also provides the covariance matrix, which I really don't understand. Can the covariance matrix be measured? This is really strange to me. I would be really appreciated if you can answer this question for me.
Thank you so much in advance for your time!
Best
Yuan

[abdul-mannan-khan]

I am also confused about it. Did you (@yuan0623 ) solve this problem? Please update. Thank you.

[RossHartley]

Apologies for the very delayed response. The covariance matrix was generated by assuming some values of encoder noise and mapping it though the kinematic Jacobian to get the 6x6 matrix.

I did this so the core library does not need the robot-specific kinematic Jacobian.

This was just an example, and I did minimal effort identifying the true encoder noise for Cassie.