Some Capabilities of a Joint GPS-LEO Navigation System

M. Rabinowitz, B.W. Parkinson and J.J. Spilker

Abstract:	The last year has seen increasing commercial interest in the combined use of positioning and two-way commu- nication, in applications ranging from emergency road- side assistance to location-based merchandising. These systems typically involve low-cost co-located GPS re- ceivers and communication transceivers, where the lat- ter device is used solely for voice or data transfer. LEO satellite systems, such as Orbcomm and Globalsltar, provide wide coverage for their data and/or voice ser- vices. We describe how the combined use of GPS and LEO signals can considerably enhance navigation per- formance, and ameliorate other shortcomings of GPS. The geometric diversity achieved by the telecom satel- lites enables the rapid, robust resolution of integer cy- cle ambiguities. We discuss the data reduction algo- rithm that has been implemented to rapidly resolve centimeter-level position without the use of ground- based pseudolites, or dual-frequency GPS receivers. In addition, using Orbcomm satellites, we experimentally demonstrate the system performance in terms of ac- curacy, and integrity of navigation solutions. We de- scribe the considerable advantages provided by LEO satellites in lossy environments, or multipath-prone en- vironments. Techniques are described which use LEOs to satisfy the FCC's E911 performance requirements when GPS signals are not trackable, such as indoors.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	255 - 265
Cite this article:	Rabinowitz, M., Parkinson, B.W., Spilker, J.J., "Some Capabilities of a Joint GPS-LEO Navigation System," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 255-265.
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