Mahmoud Abas, Full-Stack Software Engineer & AI

ROS 2 Practical - Lab 05: TurtleBot3 Simulation with RViz - Camera, LiDAR & Odometry

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ROS 2 Practical - Lab 05

TurtleBot3 Simulation with RViz

Camera, LiDAR, and odometry monitoring

Learning Objectives

Set up TurtleBot3 simulation in Gazebo
Use RViz to monitor camera and LiDAR sensors
Understand odometry data and robot pose estimation
Teleoperate TurtleBot3 and analyze sensor data for navigation

Installation

bash

sudo apt-get install gz-harmonic
sudo apt install ros-jazzy-cartographer ros-jazzy-cartographer-ros
sudo apt install ros-jazzy-navigation2 ros-jazzy-nav2-bringup
sudo apt install ros-jazzy-rviz2 ros-jazzy-rqt*

cd ros_ws/src
git clone -b jazzy https://github.com/ROBOTIS-GIT/DynamixelSDK.git
git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3_msgs.git
git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3.git
git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git
colcon build --symlink-install

Install Gazebo, the navigation/SLAM packages, and the TurtleBot3 source repos.

Environment: export TURTLEBOT3_MODEL=waffle_pi and a shared ROS_DOMAIN_ID (30) in ~/.bashrc

What is Odometry?

Odometry: Estimating position and orientation change over time from motion sensors.

Sources: wheel encoders, IMU, visual odometry
Used for dead reckoning and as an input to sensor fusion and localization

The Odometry Message

nav_msgs/msg/Odometry: Pose (with covariance) plus twist (with covariance).

text

geometry_msgs/PoseWithCovariance pose
  geometry_msgs/Pose pose
    Point position          # x, y, z
    Quaternion orientation  # rotation
  float64[36] covariance

geometry_msgs/TwistWithCovariance twist
  Twist twist
    Vector3 linear
    Vector3 angular
  float64[36] covariance

The full field layout of the Odometry message.

TurtleBot3 Sensor Suite

Camera: RGB, for visual perception
LiDAR: 360-degree laser scanner for obstacles and mapping
IMU: orientation and acceleration
Wheel encoders: feed the odometry calculation

All-in-One Lab Launch

A custom turtlebot3_lab05 package bundles monitoring tools

bash

export TURTLEBOT3_MODEL=waffle_pi
export ROS_DOMAIN_ID=30
ros2 launch turtlebot3_lab05 lab05_complete.launch.py

Launch the whole lab in one command.

Launches Gazebo with TurtleBot3
Pre-configured RViz displays
A real-time odometry monitor
A sensor data logger
All ROS-Gazebo bridges

Driving the Robot

bash

ros2 run turtlebot3_teleop teleop_keyboard

Teleoperate with the keyboard.

bash

# Manual publish alternative
ros2 topic pub --rate 10 /cmd_vel geometry_msgs/msg/TwistStamped \
'{header: {frame_id: ""},
  twist: {linear: {x: 0.2, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.1}}}'

Manual publish alternative: drive forward while turning right.

RViz Displays to Configure

Display	Topic / Style	Notes
Robot Model	Robot description	3D TurtleBot3 model
LaserScan	`/scan`	Points/spheres, about `0.1m`
Image	`/camera/image_raw`	Use compressed transport for performance
Odometry	`/odom`	Arrow plus trail of the last ~100 poses
TF	-	Visualize `base_link`, `odom`, `map` frames

Save your layout: File > Save Config As

Inspecting Topics

bash

ros2 topic list
ros2 topic info /scan
ros2 topic hz /scan
ros2 topic hz /odom
ros2 interface show sensor_msgs/msg/LaserScan
ros2 interface show nav_msgs/msg/Odometry

Commands to inspect topics and message types directly.

The TF Tree

TF: Describes spatial relationships between coordinate frames.

map

global reference

odom

drifts over time

base_footprint

base_link

robot body

camera_link

sensor frame

base_scan

sensor frame

map = global reference, odom = drifts over time, base_link = robot body
Sensor frames hang off base_link

bash

ros2 run tf2_tools view_frames
ros2 run tf2_ros tf2_echo map base_link

Inspect the TF tree directly.

Troubleshooting

`turtlebot3_gazebo` not found: clone and build turtlebot3_simulations
No robot model in RViz: check robot_state_publisher is running and URDF is published
No camera image: verify the Gazebo camera plugin and topic name
Robot not moving: check Gazebo isn't paused, confirm /cmd_vel has both a publisher and subscriber

bash

ros2 topic echo /cmd_vel --once
ros2 topic info /cmd_vel

Confirm /cmd_vel actually has a publisher and a subscriber.

Key Takeaways

Odometry estimates pose from encoders and IMU but always drifts: never treat it as ground truth alone
TurtleBot3 uses `TwistStamped` on /cmd_vel, unlike the plain Twist used in earlier labs
RViz displays (Robot Model, LaserScan, Image, Odometry, TF) are the standard sensor-monitoring toolkit
The TF tree (map to odom to base_link to sensors) defines how every sensor reading is spatially related
ros2 topic hz, ros2 topic info, and tf2_echo are the go-to commands for diagnosing "nothing is happening"
This lab is the sensor foundation for SLAM (Lab 06) and Nav2 navigation (Lab 07)

Open this lesson

Mahmoud AbasLab 05: TurtleBot3 Simulation with RViz - Camera, LiDAR & Odometry

sudo apt-get install gz-harmonic sudo apt install ros-jazzy-cartographer ros-jazzy-cartographer-ros sudo apt install ros-jazzy-navigation2 ros-jazzy-nav2-bringup sudo apt install ros-jazzy-rviz2 ros-jazzy-rqt* cd ros_ws/src git clone -b jazzy https://github.com/ROBOTIS-GIT/DynamixelSDK.git git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3_msgs.git git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3.git git clone -b jazzy https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git colcon build --symlink-install

geometry_msgs/PoseWithCovariance pose geometry_msgs/Pose pose Point position # x, y, z Quaternion orientation # rotation float64[36] covariance geometry_msgs/TwistWithCovariance twist Twist twist Vector3 linear Vector3 angular float64[36] covariance

# Manual publish alternative ros2 topic pub --rate 10 /cmd_vel geometry_msgs/msg/TwistStamped \ '{header: {frame_id: ""}, twist: {linear: {x: 0.2, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.1}}}'

Display

Topic / Style

Notes

Robot Model

Robot description

3D TurtleBot3 model

LaserScan

/scan

Points/spheres, about 0.1m

Image

/camera/image_raw

Use compressed transport for performance

Odometry

/odom

Arrow plus trail of the last ~100 poses

Visualize base_link, odom, map frames