April Tags

Learning Objectives

In this example, we show how to detect April Tags in a scene.

Getting Started

Prerequisites

ROS bridge is enabled.
Completed Cameras and Transform Trees and Odometry.
Install the apriltag-ros package for April Tag detection.
noetic_ws was sourced.

Detect April Tags

Open the April Tag example by going to Isaac Examples -> ROS -> April Tag. Three April Tags will show up in the viewport.
Open up the Stage Tree, and then open the ActionGraph by right-clicking on the prim and selecting Open Graph. The ROS Clock publisher, TF publisher and Camera Helper nodes (for initiating the camera_info and rgb image publishers) should already be setup.
Press Play to start publishing data to ROS

../_images/isaac_ros_apriltag.png

In a new terminal with your ROS environment sourced, run roslaunch isaac_tutorials apriltag_continuous_detection.launch to run the april_tag detection node.
In a new terminal with your ROS environment sourced, run rviz -d <noetic_ws>/src/isaac_tutorials/rviz/apriltag_config.rviz to start rviz and show the detections from the camera image
To see the raw data for the detected tags run rostopic echo tag_detections

../_images/isaac_ros_apriltag_rviz.png

Summary

This tutorial shows the basics of detecting April Tags in Omniverse Isaac Sim.

Next Steps

Continue on to the next tutorial in our ROS Tutorials series.

Further Learning

More on April Tags with ROS
If you wish to attach your own April Tag to objects, instructions are in April Tags