Interoperability of the Global Positioning System and Loran-C

Per K. Enge, James R. McCullough

Abstract: The Global Positioning System (GPS) is currently being installed, and when it is operational 5 satellites will be in view virtually 100 percent of the time. These satellites will provide 24-hour, global, high-accuracy service to military and civilian users at all altitudes. However, the full constellation will not be in place for several years, and even then satellite failures may introduce coverage holes. Additionally, the full constellation will not always be able to monitor its own integrity unless some external aid is used. Loran-C can be used to effectively aid GPS. A hybrid receiver can combine Loran lines of position with GPS lines of position to provide a system with great integrity, reliability, and time availability. However, the receivers must include sophisticated Loran propagation models, which account for both the spatial and temporal anomalies of the propagation paths. Indeed, without such models, the mean speed of the Loran ground wave is only predictable to a few parts in 104 overland, and a few parts in 105 over salt water. The arrival time of the Loran signal is also sensitive to seasonal and weather related changes along the propagation path. (This seasonal sensitivity can be as great as 1.2 nanoseconds per kilometer of path length.) Fortunately, GPS can be used to efficiently gather the data for these models. Additionally, GPS observations could also be used to calibrate (or tune) these models in real time.
Published in: Proceedings of the 44th Annual Meeting of The Institute of Navigation (1988)
June 21 - 23, 1988
U.S. Naval Academy
Annapolis, Maryland
Pages: 137 - 144
Cite this article: Enge, Per K., McCullough, James R., "Interoperability of the Global Positioning System and Loran-C," Proceedings of the 44th Annual Meeting of The Institute of Navigation (1988), Annapolis, Maryland, June 1988, pp. 137-144.
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