Solution: fixing missing /map

By ihsumlee , 28 February 2026
content

Great — this output means TF is now correct and complete. 🎉

 

 

What the

view_frames

result is telling you

 

 

From the text in your screenshot we can directly read the key TF chain for each robot:

 

  • robot_0/laser → parent: robot_0/base_link

  • robot_0/base_link → parent: robot_0/odom

 

 

(and similarly for robot_1, robot_2)

 

So for mapping / SLAM on robot_0, the “real TF frame names” are:

 

  • base frame: robot_0/base_link

  • odom frame: robot_0/odom

  • laser frame: robot_0/laser (but note your LaserScan message’s frame_id may be laser or robot_0/laser depending on configuration)

 

 

This is exactly what we needed earlier.

 

Also, it exported a PDF:

 

  • frames_2026-02-28_16.47.01.pdf

 

 

You can open it to visually confirm.

 

 

 

What to do next (use these frames in SLAM Toolbox params)

 

 

Open your SLAM params file:

nano ~/nav_class_ws/config/mapper_params_stage.yaml

Set these (recommended, stable):

slam_toolbox:
  ros__parameters:
    use_sim_time: true

    # Use your throttled scan if you made one
    scan_topic: /robot_0/base_scan_throttle   # or /robot_0/base_scan

    # TF frames from view_frames
    base_frame: robot_0/base_link
    odom_frame: robot_0/odom
    map_frame: map

    tf_buffer_duration: 30.0

Then restart SLAM toolbox:

ros2 launch slam_toolbox online_async_launch.py \
  slam_params_file:=/home/lee/nav_class_ws/config/mapper_params_stage.yaml

 

Quick verification

 

ros2 topic echo /map --once

If it prints, mapping is working.

 

 

 

RViz fixed frame choice (important)

 

 

Now that map will exist:

 

  • During SLAM: set RViz Fixed Frame = map

  • If SLAM not started yet: you can use robot_0/odom

 

 

 

 

Why this matters for your course

 

 

This is a perfect teaching point:

 

“Nav stacks are frame-sensitive. We don’t guess frame names; we inspect TF (view_frames) and then configure SLAM/Nav2 accordingly.”

 

 

If you want, paste one LaserScan header (from /robot_0/base_scan) showing the frame_id: line, and I’ll tell you whether SLAM toolbox should use laser or robot_0/laser (sometimes Stage uses the un-namespaced laser string inside the message).

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