In this lecture, we will continue on the previous lecture of why we may get an error message with tf_echo. Therefore we will learn about TF and query timing.

Query timing

• Transform information is continuously updated.
• Transform information publishes on the /tf topic.
• No guarantee that the query and publication time is the same!
  • • Query for a transform in a future will result in:
      “Particular source or target frame is not yet available”
    • Errors go away once the desired frames are refreshed or become available.