personalrobotics / apriltags

ROS wrapper for the Apriltags visual fiducial tracker

apriltags

ROS wrapper for the Swatbotics C++ port of the AprilTag visual fiducial detector.
The Swatbotics port uses OpenCV and CGAL for improved performance.
http://github.com/swatbotics/apriltags-cpp

The AprilTag system was originally developed by the April laboratory at the University of Michigan. http://april.eecs.umich.edu/wiki/index.php/AprilTags
E. Olson, "AprilTag: A robust and flexible visual fiducial system", IEEE International Conference on Robotics and Automation (ICRA), 2011.

Installation

Install dependencies:

$ sudo aptitude install libcgal-dev

Clone this repo into your catkin workspace and build.

Print some AprilTags

Images of the default tag family can be found in tags/36h11.ps

To open this postscript file:

$ sudo apt-get install gv
$ gv 36h11.ps

Alternatively you can download images of the tags from here:
https://april.eecs.umich.edu/wiki/index.php/AprilTags
There are *.tgz files for each family, including a *.ps file with one tag per page.

Configuration

Edit the launch file apriltags.launch

Set the default tag file parameter

param name="~default_tag_size" value="0.046"

to be the width of the black square of the tags you printed out e.g. 46mm

If your webcam does not publish images to the default topic name, you may need to edit these 2 parameters:

remap from="~image" to="/camera/rgb/image_rect"
remap from="~camera_info" to="/camera/rgb/camera_info"

For the Kinect2, they should be set too:

remap from="~image" to="/kinect2/hd/image_color_rect"
remap from="~camera_info" to="/kinect2/hd/camera_info"

Usage

$ roslaunch apriltags apriltags.launch

To check if the node can detect your printed tag:

$ rostopic echo /apriltags/detections