Interacting with 3d and 2d Mobile Maps: an Exploratory Study

To study how users of mobile maps construct the referential relationship between points in the virtual space and in the surrounding physical space, a semi-natural field study was conducted in a built city environment, utilizing a photorealistic interactive map displayed on a PDA screen. The subjects (N=8) were shown a target (building) in the physical or in the virtual space and asked to point to the corresponding object in the other space. Two viewports, “2D” (top-down) and “3D” (street-level), were compared, both allowing the users to move freely. 3D surpassed 2D in performance (e.g., 23% faster task completion) and workload measures (e.g., 53% in NASA-TLX), particularly in non-proximal search tasks where the target lied outside the initial screen. Verbal protocols and search pattern visualizations revealed that subjects utilized varied perceptual-interactive search strategies, many of which were specific to the viewport type. These strategies are set and discussed in the terms of the theory of pragmatic and epistemic action (Kirsh & Maglio, 1994). It is argued that the purpose of such strategies was not to find the target directly by transforming either of the two spaces (pragmatic action), but to make the task processing requirements better aligned with the available cognitive resources (epistemic action). Implications to interface design are discussed with examples.