1997-08-06

GPS as the Primary Navigation Sensor for ITS 972637

Intelligent Transportation Systems (ITS) require an in-vehicle infrastructure to provide adequate location information. The Global Positioning System (GPS) has been proposed as a potential technology to provide this information but has been hampered by poor performance in urban environments.Most GPS systems have been designed as stand-alone solutions that can be used in high-level system integration. Recent advances in silicon, GPS chipset architecture and software technology have enabled new methods to increase the signal availability (through rapid signal acquisition), accuracy and use of GPS solutions in difficult satellite tracking environments (using 1 or 2 satellites for updates). These improved results can be further enhanced with system integration taking advantage of data from sensors already available in most vehicles.A SiRF test vehicle was used to collect GPS position data under normal traffic conditions in downtown San Francisco (a difficult urban area for signal reception). The data was analyzed under varying scenarios to investigate the ability of this new generation GPS technology to provide nearly continuous coverage and improved accuracy. Multiple test data show that the navigation solution availability with the SiRFstar GPS receiver is near 95 percent. This leads to near continuous navigation capability when using SiRFstar GPS receiver in a hostile urban environment. Other GPS receivers tested showed lesser navigation availability under the same conditions.These results were obtained in a GPS only environment with further improvements expected through data sharing via vehicle motion sensors and spatial map information. The results and architecture used for these tests demonstrate the feasibility of the SiRFstar GPS receiver as the primary component for vehicle location information as part of an ITS system.

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