Abstract :
The Global Positioning System (GPS) provides a 24 hour, worldwide system of navigation using a constellation of US Department of Defence satellites. As GPS technology matures, new applications for positioning or tracking appear. Relatively low cost GPS receivers are now available for in-vehicle applications, often with associated map or navigation displays. Most approaches to vehicle positioning with GPS use standard receiver architectures (Original Equipment Manufacturer receiver cards) to provide an on-board navigation solution. This approach does not work well in an urban environment due to intermittent masking of satellite signals by buildings. The author describes the NAVSYS TIDGET sensor which has been developed for extremely low cost applications. Trials have been made to date for two disposable applications (weather-balloons and marine sonobuoys) and for vehicle tracking. The author concentrates on a TIDGET-Mayday adaptation for a group of applications requiring highly infrequent (`once in a lifetime´) position reporting in an urban environment
