How to read positions from tf::TransformBroadcaster

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This may be a bit of a dumb question, but how do you read poses from tf::TransformBroadcaster?

The wiki, http://wiki.ros.org/tf/Tutorials/Writ... , explains how to send poses using it, but now how to read poses (if that is something you do).

If you are not supposed to read poses from tf::TransformBroadcaster, then what exactly is the purpose of it?

When i say "read" from a tf::TransformBroadcaster, i mean to define a callback for a topic like normal