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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 offscreen. 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.

Printed maps are the most common tool to prepare people for emergency evacuation in contexts such as public buildings or transportation. Unfortunately, they are poorly understood and often ignored by people. Virtual environments (VEs) could be a more effective method to support people in acquiring spatial knowledge about the real-world environment to evacuate. This paper pursues three main goals. First, we propose a VE-based tool to support spatial knowledge acquisition for evacuation purposes, using aviation as a real-world domain in which such knowledge is crucial for passengers' safety. Second, we study in detail one of the VE design choices (active or passive navigation), comparing a version of our tool in which users navigate by actively controlling their position with another version in which users are passively led along pre-defined routes. Third, we contrast the two versions of the tool with the traditional, printed diagrammatic map provided to passengers by airlines. Results of our study show that the VE-based approach produces objectively better spatial knowledge when users are asked to pinpoint their assigned position in the environment, and that active navigation produces a performance improvement in a subsequent virtual evacuation. Moreover, the VE-based approach is perceived as more enjoyable, easier to comprehend and more effective than printed maps when active navigation is available. © 2015 Elsevier Ltd

Supporting users' navigation is a fundamental feature of mobile guides. This paper presents an experimental evaluation comparing three different ways of providing navigation guidance by combining visual and audio directions during guided city tours. The three considered solutions differ in the way audio directions are augmented with visual directions: a traditional map-based solution, a combination of a map and photographs of the area, a combination of large arrows and photographs. The results of our evaluation show that when the map is combined with photographs that clearly indicate the direction to the user or when the map is replaced by a combination of directional arrows and photographs, users' performance is significantly better. Moreover, the combination of map and photographs was highly preferred by users.

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