tional or cultural events, and the three scenarios posed in Chapter 1. Location-aware computing is a special case of broader distributed systems. The challenges intrinsic to distributed systems apply to location-aware computing as well. In addition, location-aware systems face constraints imposed by wireless communications and by the need to operate with limited computational and power resources.

This chapter explores the current state of research and key future challenges in these areas. Because the committee’s resources were limited, the discussion of current technologies focuses on the rapidly growing areas of data acquisition and delivery, which are being fueled by advances in location and orientation sensing, wireless communication, and mobile computing. Advances in these technologies could have a great effect on how geospatial data are acquired, how and with what quality they can be delivered on demand, and how mobile and geographically distributed systems are designed.

TECHNOLOGY AND TRENDS

Location-aware computing is made possible by the convergence of three distinct technical capabilities: location and orientation sensing, wireless communication, and mobile computing systems. This section summarizes the current state of these capabilities and provides some guidance on their probable future evolution.

Location and Orientation Sensing

The Global Positioning System (GPS) is the most widely known location-sensing system today. Using time-of-flight information derived from radio signals broadcast by a constellation of satellites in earth orbit, GPS makes it possible for a relatively cheap receiver (on the order of $100 today) to deduce its latitude, longitude, and altitude to an accuracy of a few meters. The expensive satellite infrastructure is maintained by the U.S. Department of Defense,1 but many civilian users benefit from the investment. Indeed, there has been a veritable explosion of GPS-based services for the consumer market over the past few years.

Although certainly important, GPS is not a universally applicable location-sensing mechanism, for several reasons. It does not work indoors, particularly in steel-framed buildings, and its resolution of a few meters is

1  

The European Union plans to launch Galileo, a purely civilian equivalent of the U.S. GPS satellite network, by 2008. See <http://www.computerworld.com/mobiletopics/mobile/story/0,10801,69580,00.html>.



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