Conceptual Framework

While navigating, wayfinders depend on route instructions to proceed along a chosen route (Lovelace et al., 1999). Such instructions are typically provided by means of a user interface on a mobile device (Westendorp et al., 2004). The most appealing user interface modalities for a mobile environment are graphical and audible interfaces. For the purpose of this work, we assume simple directional instructions described by an arrow. The instructions are deducted from the wayfinder’s closeness to the underlying region-based route. Closeness is expressed using SOCs, which require two conceptual representations of a wayfinder and a navigable route:

Wayfinder

The wayfinder is represented as a Circular Spatially Extended Point (CSEP), consisting of a position derived from a GPS unit, and a circular extent, which is given by the positional inaccuracy (also see Wuersch and Caduff, 2005).

Route

A navigable route is typically defined as a list of waypoints. Waypoints may be mod-eled as CSEPs, which allows describing a decision area around waypoints, within which wayfinders can move without getting distracted by changing instructions (Wuersch and Caduff, 2005). The route definition can be further extended by connecting two consecu-tive waypoints by an edge and by constructing regular or irregular buffers around these edges (Figure 1).
We propose a region-based route model with buffered edges. These buffer regions rep-resent properties of features in the real world, such as the geometry of a street, a park, a town square or any other navigable area.

Fig. 1:    Route models: (a) waypoints, edges, (b) waypoints, edges, and regular buffers, (c) waypoints, edges, and irregular buffers.