Stefano Burigat

Navigation in 3D virtual environments: Effects of user experience and location-pointing navigation aids

In this paper, we describe the results of an experimental study whose objective was twofold: (1) comparing three navigation aids that help users perform wayfinding tasks in desktop virtual environments (VEs) by pointing out the location of objects or places; (2) evaluating the effects of user experience with 3D desktop VEs on their effectiveness with the considered navigation aids. In particular, we compared navigation performance (in terms of total time to complete an informed search task) of 48 users divided into two groups: subjects in one group had experience in navigating 3D VEs while subjects in the other group did not. The experiment comprised four conditions that differed for the navigation aid that was employed. The first and the second condition, respectively, exploited 3D and 2D arrows to point towards objects that users had to reach; in the third condition, a radar metaphor was employed to show the location of objects in the VE; the fourth condition was a control condition with no location-pointing navigation aid available. The search task was performed both in a VE representing an outdoor geographic area and in an abstract VE that did not resemble any familiar environment. For each VE, users were also asked to order the four conditions according to their preference. Results show that the navigation aid based on 3D arrows outperformed (both in terms of user performance and user preference) the others, except in the case when it was used by experienced users in the geographic VE. In that case, it was as effective as the others. Finally, in the geographic VE, experienced users took significantly less time than inexperienced users to perform the informed search, while in the abstract VE the difference was significant only in the control and the radar conditions. From a more general perspective, our study highlights the need to take into specific consideration user experience in navigating VEs when designing navigation aids and evaluating their effectiveness.

Location-aware visualization of VRML models in GPS-based mobile guides

In this paper, we present LAMP3D, a system for the location-aware presentation of VRML content on mobile devices. We explore the application of LAMP3D in tourist mobile guides: the system is used to provide tourists with a 3D visualization of the environment they are exploring, synchronized with the physical world through the use of GPS data; tourists can easily obtain information on the objects they see in the real world by directly selecting them in the VRML world. We discuss the design and development of the system and report about the feedback obtained from the informal user testing we carried out.

Visualizing locations of off-screen objects on mobile devices: a comparative evaluation of three approaches

Browsing large information spaces such as maps on the limited screen of mobile devices often requires people to perform panning and zooming operations that move relevant display content off-screen. This makes it difficult to perform spatial tasks such as finding the location of Points Of Interest (POIs) in a city. Visualizing the location of off-screen objects can mitigate this problem: in this paper, we present a user study comparing the Halo [2] approach with two other techniques based on arrows. Halo surrounds off-screen objects with circles that reach the display window, so that users can derive the location and distance of objects by observing the visible portion of the corresponding circles. In the two arrow-based techniques, arrows point at objects and their size and body length, respectively, inform about the distance of objects. Our study involved four tasks requiring users to identify and compare off-screen objects locations, and also investigated the effectiveness of the three techniques with respect to the number of off-screen objects. Arrows allowed users to order off-screen objects faster and more accurately according to their distance, while Halo allowed users to better identify the correct location of off-screen objects. Implications of these results for mobile map-based applications are also discussed.

Navigation techniques for small-screen devices: An evaluation on maps and web pages

Several techniques have been proposed to support user navigation of large information spaces (e.g., maps or web pages) on small-screen devices such as PDAs and Smartphones. In this paper, we present the results of an evaluation that compared three of these techniques to determine how they might affect performance and satisfaction of users. Two of the techniques are quite common on mobile devices: the first one (DoubleScrollbar) is the standard combination of two scrollbars for separate horizontal and vertical scrolling with zoom buttons to change the scale of the information space, the second one (Grab&Drag) enables users to navigate the information space by directly dragging its currently displayed portion, while zooming is handled through a slider control. The last technique (Zoom-Enhanced Navigator or ZEN) is an extension and adaptation to mobile screens of Overview&Detail approaches, which are based on displaying an overview of the information space together with a detail view of a portion of that space. In these approaches, navigation is usually supported by (i) highlighting in the overview which portion of space is displayed in the detail view, and (ii) allowing users to move the highlight within the overview area to change the corresponding portion of space in the detail area. Our experimental evaluation concerned tasks involving maps as well as web page navigation. The paper analyzes in detail the obtained results in terms of task completion times, number and duration of user interface actions, accuracy of the gained spatial knowledge, and subjective preferences.

Visualizing references to off-screen content on mobile devices: A comparison of Arrows, Wedge, and Overview+Detail

When navigating large information spaces on mobile devices, the small size of the display often causes relevant content to shift off-screen, greatly increasing the difficulty of spatial tasks such as planning routes or finding points of interest on a map. Two possible approaches to mitigate the problem are Contextual Cues, i.e. visualizing abstract shapes in the border region of the view area to function as visual references to off-screen objects of interest, and Overview+Detail, i.e., simultaneously displaying a detail view and a small-scale overview of the information space. In this paper, we compare the effectiveness of two different Contextual Cues techniques, Wedge (Gustafson et al., 2008) and Scaled Arrows (Burigat et al., 2006), and a classical Overview+Detail visualization that highlights the location of objects of interest in the overview. The study involved different spatial tasks and investigated the scalability of the considered visualizations, testing them with two different numbers of off-screen objects. Results were multifaceted. With simple spatial tasks, no differences emerged among the visualizations. With more complex spatial tasks, Wedge had advantages when the task required to order off-screen objects with respect to their distance from the display window, while Overview+Detail was the best solution when users needed to find those off-screen objects that were closest to each other. Finally, we found that even a small increase in the number of off-screen objects negatively affected user performance in terms of accuracy, especially in the case of Scaled Arrows, while it had a negligible effect in terms of task completion times.

Visualizing the results of interactive queries for geographic data on mobile devices

The capabilities of current mobile computing devices such as PDAs and mobile phones are making it possible to design and develop mobile GIS applications that provide users with geographic data management and cartographic presentations in the field. However, research on how to properly support users who interact with geographic data on mobile devices is still lacking. In this paper, we present an approach to geographic data analysis that allows users to exploit interactive dynamic queries as a technique for filtering geographic information. Moreover, the proposed approach displays the results of queries through visualizations that are aimed at facing the screen estate problem typical of mobile devices. We will show how this approach can be applied to different domains by illustrating two examples of its application: (i) a decision support tool that allows tourists to search for points of interest (e.g., hotels, restaurants,...) that best satisfy their preferences and (ii) a tool allowing users to retrieve information about soil properties in a geographic area to meet a number of users constraints.

Map, diagram, and web page navigation on mobile devices: the effectiveness of zoomable user interfaces with overviews

This paper presents a study comparing two Zoomable User Interfaces with Overviews (ZUIOs) against a classic Zoomable User Interface (ZUI) in the context of user navigation of large information spaces on mobile devices. The study aims at exploring (i) if an overview is worth the space it uses as an orientation tool during navigation of an information space and (ii) if part of the lost space can be recovered by switching to a wireframe visualization of the overview and dropping semantic information in it. The study takes into consideration search tasks on three types of information space, namely maps, diagrams, and web pages, that widely differ in structural complexity. Results suggest that overviews bring enough benefit to justify the used space if (i) they highlight relevant semantic information that users can exploit during search and (ii) the structure of the considered information space does not provide appropriate orientation cues.

On the effectiveness of Overview+Detail visualization on mobile devices

Overview+Detail visualization is one of the major approaches to the display of large information spaces on a computer screen. Widely used in desktop applications, its feasibility on mobile devices has been scarcely investigated. This paper first provides a detailed analysis of the literature on Overview+Detail visualization, discussing and comparing the results of desktop and mobile studies to highlight strengths and weaknesses of the approach. The analysis reveals open issues worthy of additional investigation and can provide useful indications to interface designers. Then, the paper presents an experiment that studies unexplored aspects of the design space for mobile interfaces based on the Overview+Detail approach, investigating the effect of letting users manipulate the overview to navigate maps and the effect of highlighting possible objects of interest in the overview to support search tasks. Results of the experiment suggest that both direct manipulation of the overview and highlighting objects of interest in the overview have a positive effect on user performance in terms of the time to complete search tasks on mobile devices, but do not provide specific advantages in terms of recall of the spatial configuration of targets.

Interactive visual analysis of geographic data on mobile devices based on dynamic queries

The capabilities of current mobile devices, especially PDAs, are making it possible to design and develop mobile applications that employ visual techniques for using geographic data in the field. These applications can be extremely useful in areas as diverse as tourism, business, natural resources management and homeland security. In this paper, we present a system aimed at supporting users in the exploratory analysis of geographic data on PDAs through a highly interactive interface based on visual dynamic queries. We propose alternative visualizations to display query results and present an experimental evaluation aimed at comparing their effectiveness on a PDA in a tourist scenario. Our findings provide an experimental confirmation of the unsuitability of the typical visualization, employed by classic dynamic query systems, which displays only those results that fully satisfy a query, in those cases where only sub-optimal results are obtainable. For such cases, the results of our study highlight the usefulness of visualizations that display all results and their degree of satisfaction of the query.

Bringing dynamic queries to mobile devices: a visual preference-based search tool for tourist decision support

This paper discusses the design and development of a preference-based search tool (PBST) for tourists, operating on PDA devices. PBSTs are decision support systems that help users in finding the outcomes (e.g., multi-attribute products or services) that best satisfy their needs and preferences. Our tool is specifically aimed at filtering the amount of information about points of interest (POIs) in a geographic area, thus supporting users in the search of the most suitable solution to their needs (e.g., a hotel, a restaurant, a combination of POIs satisfying a set of constraints specified by the user). We focus on the design of an effective interface for the tool, by exploring the combination of dynamic queries to filter POIs on a map with a visualization of the degree of satisfaction of constraints set by the user. We also report the results of a usability test we carried out on the first prototype of the system.