Smart Phone and Next Generation Mobile Computing

Mobile Application Challenges 415

encountered. Clearly the accuracy of such systems relies on the

granularity of the base stations in the proximity determination. If

a location-based application employs a symbolic location represen-

tation model, then proximity-based localization techniques can be

used to localize an unknown object with respect to symbolic locations

of reference points in proximity.

7.1.3 Global Positioning System

The global positioning system (GPS) was briefly introduced in Chap-

ter 3. In short, the GPS system consists of a total number of 24 GPS

satellites orbiting the Earth, operated by the U.S. Department of

Defense. GPS satellite signals can be used by anyone free of charge. At

one time, the signals were modified so nongovernmental ...