Transformations with TF2

Lets learn about TF2 and use it to transform our laser data into the real world

By Kevin McAleer,    2 Minutes

TF2

tf2 is the ROS2 transform library, which lets the user keep track of multiple coordinate frames over time. tf2 maintains the relationship between coordinate frames in a tree structure buffered in time and lets the user transform points, vectors, etc. between any two coordinate frames at any desired point in time.

Transformations

Transformations allow us to convert (or translate) one set of coordiates to another. Our robot, and the coordinates of the parts of the robot can be considered to be local to the robot.

The robot exists in the real world (or virtual world) in a world coordinate space.

We neet to transform the data from the Lidar, know as the laser_frame (which is in the robots local coordinates), to the world coordinate space.

• Local Coordinate start at the objects origin
• Real World Coordinates have a different origin

Transformations translate coordinates between the local and real world

Laser_frame to World

We will use TF2 to create the transform from the laser_frame to the world.

• Create the Tranform with TF2 - - from the docker-desktop_ros2_1 container, type:

ros2 run tf2_ros static_transform_publisher 0 0 0 0 0 0 laser_frame world