A GPS + Dead-Reckoning Navigation System for Fleet Management

Sergio Cunha, Telmo Cunha, Phillip Tome and Luisa Bastos

Abstract:	This article presents an implementation of a GPS plus dead-reckoning sensors navigation system for fleet management applications. It is based on low-cost devices: a standard OEM GPS receiver, an odometer and a low-cost gyro. GPS information is processed in raw mode (using pseudo-ranges and dopper) together with reference station data in a tightly coupled robustness oriented filter. This enables to use GPS information in epochs when the number of visible satellites is as low as two without any heuristic assumptions of the behavior of the vehicle. Metric precision is therefore constantly maintained, even in areas severely affected by satellite signal blocking. The system was originally designed for the management of a bus fleet that included prediction of times of arrival at the bus stops. This introduced a special constraint on the information path delay. Therefore, the vehicles communicate both with the control center through a trunked radio system and with the bus stops using short range radio devices. By using two different systems, this communication network provided the adequate means to avoid information delays towards the points where they are most critical (the bus stops) and the availability of high rate navigation data in the areas where it is most needed. Differential corrections are broadcast to the vehicles in a very compact format through both systems. The goals of the article are to present: • The system architecture; • Some aspects of the navigation data processing; • The obtained accuracy, behavior and robustness; • The communications network topology and performance.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	3126 - 3130
Cite this article:	Cunha, Sergio, Cunha, Telmo, Tome, Phillip, Bastos, Luisa, "A GPS + Dead-Reckoning Navigation System for Fleet Management," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 3126-3130.
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