286 8 Accessible Global Positioning System and Related Orientation Technologies

motion sensing system, PNM, to keep it accurate. When coupled with GPS, this has the potential for a seamless indoor/outdoor location information and navigation system.

Telephone and PDA manufacturers now have integrated GPS mobile phones. These GPS cell phones will not replace the need for navigation narration from a PDA, but they will provide the ability to spot check locations and to receive periodic verbal directions. For example, I press a speed dial number, which connects me to a map server. My GPS position is sent by my phone to the server. Now, I can press “1” for nearest important location points or “2” for the nearest street intersection. The same type of information currently presented on the PDA can now be accessed by the GPS cell phone and spoken back to the user by text-to-speech software.

8.9 Chapter Summary

The difficulty of travel for the visually impaired or blind person is a significant barrier for social inclusion and personal independence. In a simple decomposition, it comprises two main areas; one is obstacle avoidance and the other is long distance navigation. Considerable thought and development has been given to trying to provide assistive technology for the two problems. In this chapter, the use of GPS technology as a contribution to the solution of the navigation problem was described and discussed.

The chapter opened with a discussion of the context of the navigation problem where issues, such as the importance of location information and the difference between mobility and navigation were considered. This led into a section on the basics of global positioning system technology; its principles, its accuracy and its shortcomings were introduced and discussed.

The middle part of the chapter was devoted to the explaining how these GPS principles are used in navigational assistive technology aids for visually impaired and blind people. Consideration was given to the design issues, how the new device should be packaged, the all important user interface and finally, the test procedures and the outcomes. Particular attention was given to the interface design as the success and adoption often crucially depends on an interface that actually meets the needs of the target end-user community. Most of this material was based on the authors’ personal experience in bringing such a navigation assistive device to the marketplace.

The final section of the chapter examined commercialisation issues and reported the authors’ experience of marketing a navigation assistive technology device. This section concluded with a brief discussion of how ongoing technological developments are likely to affect future solutions of the navigation problem for visually impaired and blind people.