Halo: Supporting Spatial Cognition on Small Screens

As users pan and zoom, display content can disappear into off-screen space, particularly on small-screen devices. 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 offscreen location of the object at the center of the ring. In our user study, participants completed all four types of map-based route planning tasks faster when using Halo then when using an arrow-based visualization technique.