This is a fork of an existing package, ar_tools, which is a ROS (Robot Operating System) wrapper for ARToolkit. This modified package enables tracking of multiple markers, as if they were a single point.

[Here] (http://vptarmigan.wordpress.com/2014/06/23/setting-up-ar_tools-ros-package/) is a short tutorial on running ROS and installing this package.

Check the [project website] (https://sites.google.com/site/umdminirobotreu2014wu/) for more info.

###Subscribed topics

• /camera/camera_info - Calibration info for camera (specific to each physical camera)
• /camera/image_raw

###Input Files Two files are required - one describing pattern info, one describing pattern transforms. Modify the parameter values below in the launch file to point to the locations of these files.

• Parameter name: marker_pattern_list
  • Specifies how many markers, and info for each marker.
  • [Example file] (https://github.com/vptarmigan/ar_tools/blob/master/ar_pose/config/multiple)
• Parameter name:marker_transforms_list
  • Specifies, for each marker, the transformation matrix relating each marker frame to a common frame.
  • [Example file] (https://github.com/vptarmigan/ar_tools/blob/master/ar_pose/config/multiple_transforms)

###Running

Make sure your camera is calibrated.

To launch with live marker tracking:

roslaunch ar_tools ar_pose_multi.launch

To launch without live marker tracking (with a recorded camera_info rosbag):

roslaunch ar_tools headless_bundle_no_rviz.launch

###Future Work/Improvements

• This package uses ar_pose as its base. If more optimization is needed, it is recommended to take a look at, ar_track_alvar, that wraps a modified and optimized version of ARToolkit.
• ARToolkit provides a built in [function] (http://www.hitl.washington.edu/artoolkit/documentation/tutorialmulti.htm), arMultiGetTransMat() that essentially tracks multiple markers as one target. That function encapsulates the algorithm in this package's ar_bundle.cpp, but is not used in this package due to time constraints + difficulty testing ARToolkit's function. Future work could be done in incorporating this function instead.