Unit 3 - Doubt about Static Broadcaster

[joseecm]

Hi,

In unit 3, when we published the static transformation between the odom and world coordinate systems the turtle robot is already displayed correctly in RVIZ.
This makes sense because by publishing the RVIZ transformation RVIZ can already know the position of each robot and therefore it can represent them.
However, I have the following doubt. It is supposed that the static transformation between odom and world is only published once. If the turtle robot then moves, shouldn’t the transformation between both coordinate systems change? How can RVIZ continue to render the turtle robot correctly?

Regards,

José Enrique.

[albertoezquerro]

Hello @joseecm ,

The odom frame is a world-fixed frame, which means it doesn’t move. Then, the local position of the robot is computed w.r.t. this odom frame. This is why we can publish an static transform from the world frame to the odom frame. You can read about it here: REP 105 -- Coordinate Frames for Mobile Platforms (ROS.org)