How to track frames from tf in ROS

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Regardless of whether you are in C++ or Python, you will want to create a tf listener object. Then you can repeatedly lookup the transform between two frames that you are interested in tracking. This looked-up transform will contain a position and quaternion that represents the transformation between the two frames of interest. Many tutorials on the wiki will use the original tf API, but these days it is probably better to use the tf2 API. See the following tutorials:

• Writing a tf2 listener Python
• Writing a tf2 listener C++