Understanding how tf is generated

First of all consult this Tutorial: Introduction to tf

Here you can see how to use these basic tf tools:

> view_frames: creates a diagram of the frames being broadcast by tf over ROS.

$ rosrun tf view_frames

Here a tf listener is listening to the frames that are being broadcast over ROS and drawing a tree of how the frames are connected. To view the tree:

$ evince frames.pdf


This is an example of the tf tree of the activity of the first ticket of Assembla in the projecto of SSC-ITESM.

If you know the frames involved, you can ask tf_echo to report the transform between any two frames broadcast over ROS.

Usage:

rosrun tf tf_echo [reference_frame] [target_frame]

"Let's look at the transform of the turtle2 frame with respect to turtle1 frame which is equivalent to \large{$$\mathbf{T}_{turtle1\_turtle2} =\mathbf{T}_{turtle1\_world} *\mathbf{T}_{world\_turtle2}$$} :

$ rosrun tf tf_echo turtle1 turtle2

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Next I read this Tutorial "Leraning tf" all in cpp: Learning tf

1) Writing a tf broadcaster (C++):