Trends in Geopositioning for Lbs, Navigation and Mapping

The Global Positioning System (GPS) is a satellite-based technology that has truly revolutionised many positioning and navigation activities, and today stands unchallenged as the ‘first choice’ position determination technology for all outdoor applications. GPS is global, works in all weather conditions, is available 24hrs a day and is free of user charges. Thanks to the revolution in microelectronics, over the last 20 years GPS has evolved into a compact, low-cost, low-power chipset that is easily integrated into mobile devices. However, GPS suffers from one important weakness, the attenuation of the GPS satellite signals indoors or under foliage is such that they cannot be tracked by conventional GPS receiver designs. During the last 10 years advances in signal processing, receiver design and the development of various “assistance” techniques has resulted in GPS now being able to be used inside buildings with varying degrees of success. Although the accuracy is not as high as in the ‘open air’, GPS signal availability does mean that this technology can be considered a candidate for integration within mobilephones, to address emergency response requirements or consumer applications such as location-based services (LBS). Modernized GPS and the new Galileo Global Navigation Satellite System (GNSS) will enhance satellite-based positioning even further. GNSS is not the only wave-based positioning technology being proposed for indoor applications. Recent research in the use of terrestrial RF signals (including “pseudolites”) shows promise that they could be used on their own, or as an augmentation to GNSS, in “hot spot” deployments. In addition, positioning via mobilephone signals themselves, or other wireless communications technologies such as WLAN and Bluetooth, is also possible. These may use range-like measurements or received signal strength, or positioning may be based on the proximity or “cell” mode. The latter mode is also used in RFID systems. Finally, a very promising non-RF solution is based on inertial technology. This paper reviews the various available technologies and comments on their suitability for LBS, navigation and traditional mapping/surveying applications.