•Recognition tasks. Rather than relying on subjects descriptive abilities, recognition tasks simplify the subject’s task by asking them to select the correct map or map segment from a multiple-choice selection where the incorrect choices are variants of the correct map, e.g. skewed or rotated.

•Qualitative approaches to studying cognitive maps. The above methods are either inherently quantitative in nature or can be easily analysed quantitatively. As with HCI, cognitive mapping researchers have made use of think-aloud protocols among other techniques, to study, for example, how people learn spatial information from maps.

Kitchin and Blades also discuss other studies—particularly ones that attempt to verify models or test subjects’ cognitive maps, e.g. comparing subjects ability to follow a route after previously following the route either in real-life or on video.

7.5.3 Overall Approach

The goals of much of human-computer interaction practice differs considerably from that of both human-computer interaction research and cognitive mapping research: both research fields are intent on understanding people whereas HCI practice is about designing systems that are easy to use. This leads to a natural focus reflected here on predominantly qualitative methods for HCI practitioners wanting to discover usability problems and quantitative methods for analysing and understanding people’s mental models.

Central to modern interactive systems design is the need for multidisciplinary teams. For the successful design of navigation systems having team members who understand cognitive mapping research and methods (in our case, particularly the work on cognitive mapping of visually impaired people) and team members who understand HCI approaches is imperative to successfully designing mobile navigation aids.

7.6 Future Positioning Technologies

Location-aware services (the awareness is limited to just location information) are the most widespread context-aware services, however even these are still in their infancy. Focussed mainly around research systems, location-aware services are starting to become more mainstream: initially driven by emergency service legislation, discussed below, and some tourism applications (e.g. Cheverst et al. 2000). As these new technologies are more widely adopted, the infrastructure will be put in place and equipment prices will drop enabling more widespread and disparate location-aware services. The key to success of many of these new services, however, is improving both the “at best” accuracy of location information and the reliability of that information in normal use. Providing navigational assistance to blind pedestrians, for example, is a major test for both accuracy and reliability, in which it is necessary to consistently know the user’s location to within about 2 m to

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provide independent navigational advice. This section provides a brief overview of some of the technological developments that might make such high accuracy location information possible, much of it is covered in more detail by the excellent reports from the Finish Personal Navigation (NAVI) programme (e.g. Kaasinen et al. 2001).

Mobile phone base stations have a geographic area, or cell, of coverage—phone calls to a mobile are directed to a given base station based on the mobile phone being last detected within a geographic cell allocated to that base station (see Figure 7.5). Approximate location-aware services can be provided by simply providing access to the cell information, e.g. a single taxi number could be provided that will be redirected to a local taxi company for the cell the mobile phone is currently, in anywhere in that country. Mobile phone cells, however, vary greatly in size: in busy urban areas, where cells are smallest and closest together, using cell information can locate a user to within 200 m. However, in rural areas the accuracy can be as low as 30 km and might not even locate the user on the correct island or country as signals travel well over water.

In the U.S.A., emergency mobile phone legislation (see http://www.fcc.gov/911/ enhanced/) required, by the end of 2005, that 95% of mobile phones were capable of giving an accurate location when an emergency (E911) call is made. (Note that similar initiatives are under way for 112 calls within the E.U.) The E911 legislation requires that the location must be provided to within 50 m for 67% of calls and 150 m for 95% of calls from location-enabled handsets. This legislation has led to considerable research into accurately providing location information at this level of detail. There are two basic approaches: make improved use of mobile phone networks to locate phones more precisely than simple cell information or augment phones with GPS technology. Both these approaches make use of existing infrastructure, e.g. base stations or satellites, reducing the costs of deployment, but add computational load to the base stations, the handsets or both. Once appropriate legal and technical frameworks are in place to protect privacy, it is likely to roll out to other services.

Mobile phone base stations can measure the transmission delay of a signal to/from a handset and the angle at which the signal is received at the base sta-

Figure 7.5. Simplified mobile phone cell model with each hexagon representing a cell area and the circle representing the actual area of signal coverage of centre cell