What is the odometry frame in relation to?

I'm trying to implement an odometry publisher for a small robot following the tutorial, but I'm confused by the terminology.

An odometry message "stores an estimate of the position and velocity of a robot in free space". It stores the estimate in free space...relative to what? If the robot doesn't know where it is, what significance does the pose variable mean? Is it simply (0,0,0)? When the robot turns, how do you update the twist without knowing your initial orientation?

Asked by Cerin on 2016-04-29 23:54:54 UTC

Comments

Answers

Odometry provides a continuous (i.e. "non jumping"), but potentially drifting motion estimate relative to some arbitrary fixed frame. The easiest fixed frame to use is the one located at (0, 0, 0) with identity orientation. Absolute poses in the odometry frame are indeed not very useful for most applications, so either velocities or differences between consecutive odometry pose estimates are used.

See also REP 105 containing a definition.

Asked by Stefan Kohlbrecher on 2016-04-30 03:06:01 UTC