The uppermost tier, called View, consists of various
user interface elements, e.g., the locationView, the
Camera View, and the specific view of a POI (i.e., the
Point of Interest View). Thereby, the Camera View
displays the data captured by the device’s camera.
Right on top of the Camera View, the locationView
is placed. It displays POIs located inside the current
field of view at their specific positions as calculated
by the Point of Interest Controller. To rotate the locationView,
the interface of the Sensor Controller is
used. The latter allows to determining the orientation
of the device. Furthermore, a radar can be used
to indicate the direction in which invisible POIs are
located (cf. Fig. 9 shows an example of the radar).
Finally, AREA make use of libraries of the mobile
development frameworks themselves, which provide
access to core functionality of the underlying operating
system, e.g., sensor access and screen drawing
functions (cf. Native Frameworks in Fig. 3).