The Transportable GPS Monitor Station

Gabe Chang, Art Gower, Tim Parker and Lee Corrie

Abstract:	The Global Positioning System (GPS) Operational Control Segment since its inception has collected data from 5 GPS Monitor Stations. The Monitor Stations are located in Colorado Springs, Ascension Island, Diego Garcia, Kwajelien Atoll, and Hawaii. The current locations provide coverage of GPS satellites approximately 98% of the time (when there are no Monitor Station failures). While this coverage was adequate for the war-fighter of the 8Os, current applications, both civilian and military, will benefit from increased monitoring capabilities. The United States Air Force has already started to address the problem of limited MS coverage by planning the use of existing Defense Mapping Agency (DMA) GPS monitoring sites as additional data sources. The use of additional monitoring sites increases the number of observations, the spatial diversity of observations, and offers the opportunity for improved integrity assurance. These extra observations will improve both the clock and ephemeris estimates for the GPS navigation message with their incorporation into the operational Kalman filter. But use of the DMA monitoring sites is just the beginning. There is a need for the Air Force to have greater redundancy and spatial diversity of measurements, especially in areas of increased military responsibility. This paper explores the concepts and benefits of a Transportable Monitor Station (TMS). The ability of the GPS Control Segment to get accurate GPS measurements close to an area where GPS performance is critical will enable more accurate and reliable information to be provided to the personnel and equipment that need it most. In the simplest form, deployment of one or more TMSs near, but outside of, the area of responsibility allows the OCS to ensure the integrity of the navigation service for that area. Using methods such as the Wide Area GPS Enhancement (WAGE), the level of accuracy in the theater can also be significantly improved. Where improved system accuracy is needed, several TMSs along with a deployable wide-area correction generation and communication system, can be used to provide the entire area of responsibility with secure, highly accurate GPS correction information. This paper will explore the requirements for a TMS, give three different operational scenarios for its use, and provide two preliminary designs for its implementation.
Published in:	Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996) June 19 - 21, 1996 Royal Sonesta Hotel Cambridge, MA
Pages:	57 - 63
Cite this article:	Chang, Gabe, Gower, Art, Parker, Tim, Corrie, Lee, "The Transportable GPS Monitor Station," Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996), Cambridge, MA, June 1996, pp. 57-63.
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