AIDING GPS WITH CALIBRATED LORAN-C

Per K. Enge and James R. McCullough

Peer Reviewed

Abstract:	GPS is currently being installed; when it is operational, five satellites will be in view virtually 100 percent of the time. However, the full constellation will not be in place for several years, and even then satellite failures may introduce coverage holes. Additionally, even with the full constellation, a GPS receiver will not always be able to monitor signal integrity unless some external aid is used. Loran-C can be used effectively to 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. Indeed, Loran is independent of GPS and can be used to detect GPS system or receiver failures. However, the hybrid receivers must include sophisticated Loran propagation models, which account for both the spatial and temporal anomalies of the propagation paths. Fortunately, GPS can be used to efficiently gather the data for these models. Additionally, GPS observations could be used to calibrate (or tune) these models in real time. This paper reviews the theory of Loran propagation and gives a basic Loran pseudorange model. It also presents some basic approaches for combining Loran and GPS pseudoranges in a position-fixing receiver. Finally, it estimates the accuracy of the hybrid system.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 35, Number 4
Pages:	469 - 482
Cite this article:	Enge, Per K., McCullough, James R., "AIDING GPS WITH CALIBRATED LORAN-C", NAVIGATION: Journal of The Institute of Navigation, Vol. 35, No. 4, Winter 1988-1989, pp. 469-482.
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