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Static Transforms

Static transforms pin down the fixed geometric relationships between frames — where sensors sit on the body, and how each robot's map frame relates to the world frame — so that every module can transform data into a common frame without per-module configuration. On the robot they come from two places, both set up by the launch preamble in autonomy_bringup/launch/robot.launch.xml, which runs for every stack.

The Frame Tree

  • world — fixed origin
  • map — child of world (static identity); ENU, meters — the planning/state frame
  • base_link — the body frame, positioned by the state estimate; sensor frames hang off it via the URDF

world → map

The preamble publishes a static identity transform world → map via tf2_ros static_transform_publisher (node world_to_map_broadcaster). world is the fixed origin; map is the ENU planning/state frame in which odometry pose, the global plan, and the map live. The dynamic map → base_link relationship comes from the state estimate, not a static transform.

Sensor Extrinsics (URDF)

Sensor and body-frame extrinsics are published by robot_state_publisher from the robot URDF: the preamble includes robot_descriptions/launch/robot_state_publisher.launch.py with the urdf_file launch argument, which defaults to the URDF_FILE environment variable. URDF_FILE is set in the top-level .env (default: robot_descriptions/iris/urdf/iris_with_sensors.pegasus.robot.urdf) and passed into the robot container by robot/docker/robot-base-docker-compose.yaml; fleet files can override it per robot via their vehicle definition.

See Also