ROS2 Transform Listener

Problem Statement

Implement a ROS2 node that reads the coordinate transform between two frames from the TF2 tree and logs the result.

Requirements

Your node must:

• Create a tf2_ros.Buffer and a tf2_ros.TransformListener attached to it
• Use a create_timer(1.0, ...) to periodically look up the transform from 'base_link' to 'map'
• Call self.tf_buffer.lookup_transform('map', 'base_link', rclpy.time.Time()) to get the latest available transform
• Handle all three TF2 exceptions gracefully: LookupException, ConnectivityException, ExtrapolationException
• On success, log the translation (x, y, z) and rotation (x, y, z, w) with self.get_logger().info()
• Log "TF2 Listener Ready" on startup

Input / Output

Input: Transforms published on /tf and /tf_static (consumed automatically by TransformListener)

Output: Periodic log lines showing translation and rotation from base_link → map

🤖 Why This Matters in Real Robots

Every Nav2 planner, every perception pipeline, and every arm controller reads TF2. When you call lookup_transform('map', 'base_link', Time()) you get the robot's current position in the world frame — the same call that Nav2's costmap, the move_base equivalent, and RViz2 all make internally hundreds of times per second.

⚠️ Common Pitfalls

• Not passing the node to TransformListener: TransformListener(self.tf_buffer, self) — the second argument is the node, which provides the clock and executor context. Miss it and the buffer never gets populated.
• Using rclpy.time.Time() vs a specific stamp: Time() means "latest available". Passing a specific stamp requires that transform to exist in the buffer at exactly that time — usually not what you want.
• Not catching all three exceptions: TF2 raises different exceptions for different failure modes. Catching only LookupException will crash your node on startup when frames haven't been published yet.