A Future GNSS Concern on the Modernization of GPS and the Evolution of Galileo

Keith D. McDonald

Abstract:	The modernization of GPS has been proceeding for the past several years based on discussions, recommendations, and plans that have occurred over most of the last decade. Also, coordination, planning and activities in Europe relating to the commitment by the European Union to the implementation of the Galileo navigation satellite system have cautiously but steadily advanced considerably during this same period. Both systems offer desirable capabilities on their own and even greater performance and other capabilities in combination. These advantages are reasonably well known and have been documented extensively. This paper summarizes many of the current and planned features of GPS and its modernization and addresses these capabilities in the perspective of the plans for the Galileo system. The time lines for the provision of the planned services by each system are analyzed and an attempt is made to place the schedules into a realistic perspective based upon historical GPS implementation data. A serious concern relating to significant delays in the GPS capabilities planned for the civil sector, especially those provided to safety, is identified and discussed. The basic concern is the decade long interval between the time when full capabilities for Galileo are available and when full civil GPS capabilities are available. Some recommendations are provided for first, recognition of the deficiency by appropriate authorities and second, proposed steps for addressing and possibly resolving this serious concern. Initially, a summary is given of the performance characteristics, i.e., the operating modes and capabilities, of GPS. This includes stand-alone, code differential, carrier phase differential and Interferometric attitude (angle) measurements. Next, the new signals and signal structures and the resulting performance improvements, and in certain cases new capabilities, that result from the modernization of GPS are addressed. A summary chart relating to the capabilities and schedule currently planned for GPS in the next fifteen years and beyond is presented and discussed. Similar data for Galileo is presented and analyzed in the context of the performance and a realistic schedule for GPS. Institutional, funding, policy and planning concerns for both GPS and Galileo are addressed in the context of the factors that may influence, and normally delay, the implementation of the systems. A comparison is provided for the civil user capabilities provided by each system. A serious schedule anomaly is identified and discussed relating especially to a significant delay in the implementation of the safety-related services of GPS.
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:	2804 - 2827
Cite this article:	McDonald, Keith D., "A Future GNSS Concern on the Modernization of GPS and the Evolution of Galileo," 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. 2804-2827.
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