INTERACTIONS.ACM.ORG 54 INTERACTIONS JULY–AUGUST2014
The boundaries between ‘the digital’ and our everyday physical world are dissolving as we develop more physical ways of
interacting with computing. This forum presents some of the topics discussed in the colorful multidisciplinary field of
tangible and embodied interaction. — Eva Hornecker, Editor
FORUM LET'S GET PHYSICAL

around the world still use paper flight strips. Printed on each strip is the planned route of an aircraft through a controller’s sector of responsibility.

Controllers annotate, grasp, move, and organize their paper strips on a stripboard, using these tangible interactions to organize their mental picture [ 2].

Unfortunately, paper strips are a poor connection between the physical and digital worlds: Once printed they cannot be updated, nor can the instructions given to pilots be used as input to the system. This impedes the development of more automated ATC systems in which controllers would be provided with useful alerts and hints computed from their instructions.

However, universal solutions for replacing paper with fully digital systems have yet to be found. The proposal to use graphical interfaces on the sole radar display met with mixed results. More sophisticated variants of “electronic stripping” were then proposed, culminating

Air traffic control (ATC) guides aircraft o maintain safe distances and to ptimize traffic fluidity. ATC has been a life-size HCI laboratory for many decades, as witnessed by the introduction of touchscreens in the 1960s, digital emulations of paper in the 1990s [ 1], and research on augmented reality [ 2]. This history reveals a succession of compromises between physical and digital interactions, of which tangible user interfaces might be the synthesis.

What makes ATC special is the combination of efficiency and safety that shapes its evolution. While efficiency is the driving force for technical innovation, safety is a selection force: Only those innovations for which air traffic controllers can safely adapt their working methods are put into operation.

This co-evolution of technologies and working methods is a strong asset of ATC. However, it also makes life hard for engineers because of the difficulty in establishing exactly how a technology will contribute to safety before proposing it as an alternative to current technologies.

An example of this challenging evolution process is the switch from paper to digital media, fostered by the civil aviation agencies since the mid-

1980s, but still not achieved. Almost everywhere, controllers monitor traffic through real-time radar displays and communicate with pilots by radio.

In addition, to anticipate the traffic,
manage their decisions, and program
their actions, many controllers
with combinations of rich graphics,
animation, touch, and gestures [ 1].
These have encountered some success,
but in many cases, particularly in
airports, there is still a need for the
better capturing properties of paper
strips. Combining the benefits of paper
with those of digital through tangible
interaction is a promising direction for
meeting these demands.

THE STRIP’TIC PROTOTYPE We have designed Strip’ TIC (Stripping Tangible Interface for Controllers), a prototype that combines augmented paper and digital pens on a multitouch glass stripboard, using vision-based tracking and augmented rear and front projection [ 3]. The paper strips, the stripboard, and the radar screen are all covered with Anoto Digital Pen patterns (DP-patterns), small patterns used by the pen’s infrared digital camera to compute the location of the pen on the dotted surface. The controllers’ actions with the digital pen are sent in real time to the software. They can annotate paper strips, and the resulting strokes are both physical (inked) and digital (projected). They can use the pen to point at symbols on the radar display or names on the paper strips. The stripboard itself is semi-opaque. This enables both a bottom projection on the stripboard and strip tracking, thanks to AR patterns printed on the back of the strips. A second projector located above the device displays graphics on top of the stripboard and the strips.

Designed in close collaboration with controllers, Strip’TIC allows them to manage traffic and workload with their current rules and practices while

Jean-Luc Vinot, Université de Toulouse - ENAC, Catherine Letondal, Université de Toulouse - ENAC,

Rémi Lesbordes, DSNA/DTI/R&D, Stéphane Chatty, Université de Toulouse - ENAC,

Stéphane Conversy, Université de Toulouse - ENAC, Christophe Hurter, Université de Toulouse - ENAC

Tangible Augmented Reality
for Air Traffic Control

Insights
→ Air traffic control procedures, skills,
and systems have co-evolved over
decades in a design process involving
controllers, programmers, and
paper/electronic technologies.

→ Tangible interaction combined with augmented reality is well suited for supporting ATC. Developing these systems is challenging yet feasible.

→ Tangible augmented interactors should be conceived of as continuous physical/virtual artifacts.