Sensor configuration and Noise levels about ethzasl_msf HOT 7 CLOSED

@flaviofontana sorry for the delay on this. I agree with your suggestion and I would be happy see these fixed in the framework. The unit of the measurement noise on the orientation is expressed in radians.

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I'm glad to see your improvement. I was struggling with this "unit problem".

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@simonlynen Thanks for your reply I started working on integrating the comments, I also took the liberty to modify the pose_sensor config file and add comments. Let me know if this approach is ok for you
https://github.com/flaviofontana/ethzasl_msf/commit/d8afeffa65ebaac63560ce0fd059dde147fc9e6f

I still have two open questions

• in your config you estimate for example the scale, however you set the process noise to zero, is this correct or should we set it to something small (what is small)?
  pose_sensor/pose_fixed_scale: false pose_sensor/pose_noise_scale: 0.0
• for pose_noise_meas_q do you use the convention of the ros pose msg?
  meaning I can compute this value from experimental data as follows
  • record N+1 orientation measurements with sensor at rest -> q0, .... , qN
  • transform the N quaternion to the three euler angles -> phi0, ... phiN; theta0,... thetaN; psi0,...,psiN
  • compute the std dev for each angle phi, theta, psi -> take the mean of the three

cheers,
flavio

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@flaviofontana yes, the changelist looks great!

qs:

1. We usually have seen no large scale drifts and thus prefered to keep the covariance for the scale a bit tighter by leaving it at zero.
2. yes that would be ok to do. Of course it is better if you get these values from your pose-computation algorithm and not use a fixed measurement noise covariance.

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@simonlynen Thanks again for your answers.

1. but even with 0 covariance the scale will be estimated?
   For the examle config, should be set it to e-10 just to make a point that when somevalue it not fixed processnoise needs to be defined?

I will finish it tmrw and send then a pull request.

flavio

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@flaviofontana yes, the additional inflation of the covariance for the scale estimate can be used to model larger drifts in the scale of the SLAM system. The scale is estimated independently from that.

I would prefer if you left it at zero like the covariance inflation on the extrinsic calibration.

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@flaviofontana Please take a look at this definitions here and try to either point to these or adopt as much of the notation as possible: https://github.com/ethz-asl/kalibr/wiki/IMU-Noise-Model-and-Intrinsics

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