ROS Apriltag detector package

This repository has ROS/ROS2 nodes and nodelets/components for detecting Apriltags using the Apriltag 3 library.

Supported platforms

Currently builds under Ubuntu 22.04 with ROS2 Humble or later.

How to build

Create a workspace (~/ws), clone this repo, and use vcs to pull in the remaining dependencies:

pkg=apriltag_detector
mkdir -p ~/$pkg/src
cd ~/ws
git clone https://github.com/ros-misc-utilities/${pkg}.git src/${pkg}

On ROS1 you also need the messages package:

cd src
vcs import < ${pkg}/${pkg}.repos
cd ..

Install all system packages that this package depends on:

rosdep install --from-paths src --ignore-src

configure and build on ROS1:

catkin config -DCMAKE_BUILD_TYPE=RelWithDebInfo  # (optionally add -DCMAKE_EXPORT_COMPILE_COMMANDS=1)
catkin build

configure and build on ROS2:

cd ~/ws
colcon build --symlink-install --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo  # (optionally add -DCMAKE_EXPORT_COMPILE_COMMANDS=1)

How to use

Examine the launch file and adjust the topic remapping, tag family etc. Then start as follows (assuming your camera publishes under /my_camera_name/image_raw):

ROS1:

roslaunch apriltag_detector node.launch camera:=my_camera_name
rqt_image_view

The detector publishes a debug image and a tag topic.

ROS2:

ros2 launch apriltag_detector node.launch.py camera:=my_camera_name
ros2 run rqt_image_view rqt_image_view

Parameters:

• tag_family. Apriltag family, something like "tf36h11".
• max_hamming_distance. Maximum allowable hamming distance (defaults to 0).
• decimate_factor. By how much to decimate the image to speed up detection. Defaults to 1 (no decimation). To half the resolution, use decimate_factor=2.
• blur. Gaussian blur to apply. Defaults to 0 (no blur). Can be negative to sharpen.
• image_qos_profile. QoS profile of image messages that are subscribed to. Defaults to default, but can also be set to sensor_data. Use this parameter to achieve QoS compatibility when subscribing to image data.
• num_threads. Number of threads on which the Apriltag library will operate. Defaults to 1.

License

This software is issued under the Apache License Version 2.0.

Changelog for package apriltag_detector

1.1.1 (2024-03-02)

• added missing dependency on ros_environment
• Contributors: Bernd Pfrommer

1.1.0 (2024-02-09)

• initial release
• Contributors: Bernd Pfrommer