Florian Alt

Requirements and design space for interactive public displays

Digital immersion is moving into public space. Interactive screens and public displays are deployed in urban environments, malls, and shop windows. Inner city areas, airports, train stations and stadiums are experiencing a transformation from traditional to digital displays enabling new forms of multimedia presentation and new user experiences. Imagine a walkway with digital displays that allows a user to immerse herself in her favorite content while moving through public space. In this paper we discuss the fundamentals for creating exciting public displays and multimedia experiences enabling new forms of engagement with digital content. Interaction in public space and with public displays can be categorized in phases, each having specific requirements. Attracting, engaging and motivating the user are central design issues that are addressed in this paper. We provide a comprehensive analysis of the design space explaining mental models and interaction modalities and we conclude a taxonomy for interactive public display from this analysis. Our analysis and the taxonomy are grounded in a large number of research projects, art installations and experience. With our contribution we aim at providing a comprehensive guide for designers and developers of interactive multimedia on public displays.

Looking glass: a field study on noticing interactivity of a shop window

In this paper we present our findings from a lab and a field study investigating how passers-by notice the interactivity of public displays. We designed an interactive installation that uses visual feedback to the incidental movements of passers-by to communicate its interactivity. The lab study reveals: (1) Mirrored user silhouettes and images are more effective than avatar-like representations. (2) It takes time to notice the interactivity (approx. 1.2s). In the field study, three displays were installed during three weeks in shop windows, and data about 502 interaction sessions were collected. Our observations show: (1) Significantly more passers-by interact when immediately showing the mirrored user image (+90%) or silhouette (+47%) compared to a traditional attract sequence with call-to-action. (2) Passers-by often notice interactivity late and have to walk back to interact (the landing effect). (3) If somebody is already interacting, others begin interaction behind the ones already interacting, forming multiple rows (the honeypot effect). Our findings can be used to design public display applications and shop windows that more effectively communicate interactivity to passers-by.

Location-based crowdsourcing: extending crowdsourcing to the real world

The WWW and the mobile phone have become an essential means for sharing implicitly and explicitly generated information and a communication platform for many people. With the increasing ubiquity of location sensing included in mobile devices we investigate the arising opportunities for mobile crowdsourcing making use of the real world context. In this paper we assess how the idea of user-generated content, web-based crowdsourcing, and mobile electronic coordination can be combined to extend crowdsourcing beyond the digital domain and link it to tasks in the real world. To explore our concept we implemented a crowd-sourcing platform that integrates location as a parameter for distributing tasks to workers. In the paper we describe the concept and design of the platform and discuss the results of two user studies. Overall the findings show that integrating tasks in the physical world is useful and feasible. We observed that (1) mobile workers prefer to pull tasks rather than getting them pushed, (2) requests for pictures were the most favored tasks, and (3) users tended to solve tasks mainly in close proximity to their homes. Based on this, we discuss issues that should be considered during designing mobile crowdsourcing applications.

How to evaluate public displays

After years in the lab, interactive public displays are finding their way into public spaces, shop windows, and public institutions. They are equipped with a multitude of sensors as well as (multi-) touch surfaces allowing not only the audience to be sensed, but also their effectiveness to be measured. The lack of generally accepted design guidelines for public displays and the fact that there are many different objectives (e.g., increasing attention, optimizing interaction times, finding the best interaction technique) make it a challenging task to pick the most suitable evaluation method. Based on a literature survey and our own experiences, this paper provides an overview of study types, paradigms, and methods for evaluation both in the lab and in the real world. Following a discussion of design challenges, we provide a set of guidelines for researchers and practitioners alike to be applied when evaluating public displays.

Cruise Control for Pedestrians: Controlling Walking Direction using Electrical Muscle Stimulation

Pedestrian navigation systems require users to perceive, interpret, and react to navigation information. This can tax cognition as navigation information competes with information from the real world. We propose actuated navigation, a new kind of pedestrian navigation in which the user does not need to attend to the navigation task at all. An actuation signal is directly sent to the human motor system to influence walking direction. To achieve this goal we stimulate the sartorius muscle using electrical muscle stimulation. The rotation occurs during the swing phase of the leg and can easily be counteracted. The user therefore stays in control. We discuss the properties of actuated navigation and present a lab study on identifying basic parameters of the technique as well as an outdoor study in a park. The results show that our approach changes a users walking direction by about 16°/m on average and that the system can successfully steer users in a park with crowded areas, distractions, obstacles, and uneven ground.

Increasing the security of gaze-based cued-recall graphical passwords using saliency masks

With computers being used ever more ubiquitously in situations where privacy is important, secure user authentication is a central requirement. Gaze-based graphical passwords are a particularly promising means for shoulder-surfing-resistant authentication, but selecting secure passwords remains challenging. In this paper, we present a novel gaze-based authentication scheme that makes use of cued-recall graphical passwords on a single image. In order to increase password security, our approach uses a computational model of visual attention to mask those areas of the image that are most likely to attract visual attention. We create a realistic threat model for attacks that may occur in public settings, such as filming the users interaction while drawing money from an ATM. Based on a 12-participant user study, we show that our approach is significantly more secure than a standard image-based authentication and gaze-based 4-digit PIN entry.

Designing shared public display networks: implications from today's paper-based notice areas

Large public displays have become a regular conceptual element in many shops and businesses, where they advertise products or highlight upcoming events. In our work, we are interested in exploring how these isolated display solutions can be interconnected to form a single large network of public displays, thus supporting novel forms of sharing access to display real estate. In order to explore the feasibility of this vision, we investigated todays practices surrounding shared notice areas, i.e. places where customers and visitors can put up event posters and classifieds, such as shop windows or notice boards. In particular, we looked at the content posted to such areas, the means for sharing it (i.e., forms of content control), and the reason for providing the shared notice area. Based on two-week long photo logs and a number of in-depth interviews with providers of such notice areas, we provide a systematic assessment of factors that inhibit or promote the shared use of public display space, ultimately leading to a set of concrete design implication for providing future digital versions of such public notice areas in the form of networked public displays.

Audience behavior around large interactive cylindrical screens

Non-planar screens, such as columns, have been a popular means for displaying information for a long time. In con-trast to traditional displays their digital counterparts are mainly flat and rectangular due to current technological constraints. However, we envision bendable displays to be available in the future, which will allow for creating new forms of displays with new properties. In this paper we ex-plore cylindrical displays as a possible form of such novel public displays. We present a prototype and report on a user study, comparing the influence of the display shape on user behavior and user experience between flat and cylindrical displays. The results indicate that people move more in the vicinity of cylindrical displays and that there is no longer a default position when it comes to interaction. As a result, such displays are especially suitable to keep people in motion and to support gesture-like interaction.

P-LAYERS -- A Layered Framework Addressing the Multifaceted Issues Facing Community-Supporting Public Display Deployments

The proliferation of digital signage systems has prompted a wealth of research that attempts to use public displays for more than just advertisement or transport schedules, such as their use for supporting communities. However, deploying and maintaining display systems “in the wild” that can support communities is challenging. Based on the authors’ experiences in designing and fielding a diverse range of community-supporting public display deployments, we identify a large set of challenges and issues that researchers working in this area are likely to encounter. Grouping them into five distinct layers -- (1) hardware, (2) system architecture, (3) content, (4) system interaction, and (5) community interaction design -- we draw up the P-LAYERS framework to enable a more systematic appreciation of the diverse range of issues associated with the development, the deployment, and the maintenance of such systems. Using three of our own deployments as illustrative examples, we will describe both our experiences within each individual layer, as well as point out interactions between the layers. We believe our framework provides a valuable aid for researchers looking to work in this space, alerting them to the issues they are likely to encounter during their deployments, and help them plan accordingly.

Pervasive Displays: Understanding the Future of Digital Signage

Fueled by falling display hardware costs and rising demand, digital signage and pervasive displays are becoming ever more ubiquitous. Such systems have traditionally been used for advertising and information dissemination, with digital signage commonplace in shopping malls, airports and public spaces. While advertising and broadcasting announcements remain important applications, developments in sensing and interaction technologies are enabling entirely new classes of display applications that tailor content to the situation and audience of the display. As a result, signage systems are beginning to transition from simple broadcast systems to rich platforms for communication and interaction. In this lecture, we provide an introduction to this emerging field for researchers and practitioners interested in creating state-of-the-art pervasive display systems. We begin by describing the history of pervasive display research, providing illustrations of key systems, from pioneering work on supporting collaboration to contemporary systems designed for personalized information delivery. We then consider what the near future might hold for display networks -- describing a series of compelling applications that are being postulated for future display networks. Creating such systems raises a wide range of challenges and requires designers to make a series of important trade-offs. We dedicate four chapters to key aspects of pervasive display design: audience engagement, display interaction, system software, and system evaluation. These chapters provide an overview of current thinking in each area. Finally, we present a series of case studies of display systems and our concluding remarks.