Calculate covariance matrix from x,y,z data of /odom

Question

I've recorded a bag file from a custom robot (in real world) that does not provide covariane matrix and I want to use /odom to feed an ekf, but covariance matrix is 0. How can I calculate it?

It's a sample of /odom:

pose: 
  pose: 
    position: 
      x: 0.082
      y: 0.507
      z: 0.0
    orientation: 
      x: 0.0
      y: 0.0
      z: -0.789272088731
      w: 0.614043622188
  covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
twist: 
  twist: 
    linear: 
      x: 0.104
      y: 0.0
      z: 0.0
    angular: 
      x: 0.0
      y: 0.0
      z: 0.0663225115758
  covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

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Originally posted by maysamsh on ROS Answers with karma: 139 on 2013-11-06

Post score: 0

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Original comments

Comment by KDROS on 2015-01-15:
which package you are using? Your question may help me in some points. I am also facing same problem. I want to use robot_localization package.

Answer 1

you can use diagonal matrix for the covariance. each element in the diagonal entries is your best expectation about the odom variance.

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Originally posted by Anas Alhashimi with karma: 179 on 2015-01-15

This answer was ACCEPTED on the original site

Post score: 1

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Original comments

Comment by KDROS on 2015-01-15:
Anas, its very old question, and the person is not looking here from last june.

Comment by Anas Alhashimi on 2015-01-16:
It is better late than never :)

Comment by KDROS on 2015-01-16:
Hmm.. Impressive.