[ros-users] Q about covariance matrices in nav_msgs/Odometry

Wim Meeussen meeussen at willowgarage.com
Tue Nov 16 21:09:09 UTC 2010


> I am trying to create a nav_msgs/Odometry publisher, to be used by
> the robot_pose_ekf  node.  My robot only give me 3 numbers: x,y and theta
> while the nav_msgs/Odometry message needs covariance and many other data.
> My question is what variables correspond to the covariance matrices
> in nav_msgs/Odometry?

Check out the message documentation here:
You'll basically need a 6x6 matrix to represent the Gaussian
uncertainty on your robot pose. If you only have 3 values from your
odometry, you probably want to use high covariance values
corresponding to the other 3 values in the robot pose.  If you want to
see an example, you can start up a pr2 robot in Gazebo, and do a
rostopic echo on the output of the base_odometry controller.

Hope this helps,


Wim Meeussen
Willow Garage Inc.

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