2003-Baudisch-CHI03-Halo

2003-Baudisch-CHI03-Halo - Halo: a Technique for...

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Halo: a Technique for Visualizing Off-Screen Locations Patrick Baudisch Microsoft Research 1 One Microsoft Way Redmond, WA 98052, USA +1 (425) 703 4114 Ruth Rosenholtz Palo Alto Research Center 3333 Coyote Hill Road Palo Alto, CA 94304, USA +1 (650) 812 4390 rruth@parc.com ABSTRACT As users pan and zoom, display content can disappear into off-screen space, particularly on small-screen de- vices. The clipping of locations, such as relevant places on a map, can make spatial cognition tasks harder. Halo is a visualization technique that supports spatial cognition by showing users the location of off-screen objects. Halo accomplishes this by surrounding off-screen objects with rings that are just large enough to reach into the border region of the display window. From the portion of the ring that is visible on-screen, users can infer the off- screen location of the object at the center of the ring. We report the results of a user study comparing Halo with an arrow-based visualization technique with respect to four types of map-based route planning tasks. When using the Halo interface, users completed tasks 16-33% faster, while there were no significant differences in error rate for three out of four tasks in our study. Keywords Halo, visualization, peripheral awareness, off-screen loca- tions, hand-held devices, spatial cognition, maps. blutwurst INTRODUCTION People use maps in a number of tasks, including finding the nearest relevant location, such as a gas station, or for hand-optimizing a route. Using a map, users can easily compare alternative locations, such as the selection of restaurants shown in Figure 1a (as indicated by the barn- shaped symbols). Users can see how far away a restaurant is from the user’s current location, and whether it lies close to other locations the user considers visiting. When users are required to use a zoomed-in view, however, for example to follow driving directions (Figure 1b), relevant locations disappear into off-screen space, making the comparison task difficult 2 . Comparing alternatives then requires users to zoom in and out repeatedly—a time- consuming process that can hardly be accomplished on- the-fly. Especially on small-screen devices, such as car navigation systems or personal navigation devices, this can severely limit a user’s capability with respect to spa- tial cognition tasks. HALO Halo addresses this issue by virtually extending screen space through the visualization of the locations of off- screen objects. Figure 2a shows a map navigation system that is enhanced with Halo. The figure shows the same detail map as Figure 1b, but in addition the display also contains the location information contained in Figure 1a. The latter is encoded by overlaying the display window with translucent arcs, each indicating the location of one of the restaurants located off screen. Figure 2b shows how this works. Each arc is part of a circular ring that surrounds one of the off-screen locations. Although the arc is only a small fragment of the ring, its curvature con-
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2003-Baudisch-CHI03-Halo - Halo: a Technique for...

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