Information at a Glance

ersonal digital assistants (PDAs) combined with wireless networking are beginning to let mobile users access the same information they once used only from the office or at home. However, researchers have long realized that it's important not to treat mobile computing simply as a scaled-down version of desktop computing. Rather, mobility has profound consequences for the way in which we use computers. 1 For example, desktop users might concentrate on a computer display for long periods, but mobile users are often mobile because they want to interact with the world around them. Consequently, a common situation when using a PDA to find information about our immediate environment is to continuously switch between looking around and looking at the PDA display. What if we could instead visualize and interact with information directly in the context of our surround-ings? Our research group is exploring how augmented reality 2 (AR) could someday make this possible. AR integrates a complementary virtual world with the physical world—for example, by using head-tracked see-through head-worn displays to overlay graphics on what we see. Instead of looking back and forth between the real world and a PDA, we look directly at the real world and the virtual information overlaid on it. At the heart of this approach is context-aware computing, 3 computing systems that are sensitive to the context in which they operate, ranging from human relationships to physical location. For example, information might be tied to specific locations within a global, Earth-centered, coordinate system. 4 How can we design effective mobile AR user inter-faces? We've been trying to answer this question in part by developing the experimental AR research prototypes we describe here. In AR, as in work on information visu-alization using desktop technologies, the amount of information available can far exceed what a system can legibly display at a given time, necessitating information filtering. Julier et al. 5 have developed information filtering techniques for AR that depend on the user's goals, object importance, and proximity. In the descriptions that follow, we assume that a system can accomplish information filtering of this sort and that our system is displaying everything it should. We're especially interested in how an AR system could provide information at a glance to aid a mobile user exploring an unfamiliar environment. Such a user might be a tourist visiting a foreign city or a native trying to find a building from its address. …