CROSS-RATE SYNCHRONIZATION OF LORAN-C USING GPS

Per K. Enge and Gary Noseworthy

Peer Reviewed

Abstract:	Loran-C transmitters are grouped into different chains, each with a specified group repetition interval (GRI) or group repetition rate (l/GRI). Currently, Loran-C transmitters in different chains are not tightly synchronized. Consequently, Loran receivers can compute time differences only between signals with the same GRI. In other words, they require at least two received signals from each GRI they wish to use. If the receiver can receive many stations within a GRI, this limitation is not troublesome. However, if the receiver is near the edge of coverage or if a transmitter has failed, it can be helpful to remove this limitation and allow the receiver to compute cross-rate time differences. The time transfer capability of GPS is one way of accomplishing the required cross-rate synchronization. In this paper, we examine (by example) the impact of cross-rate synchronization on Loran-C coverage. We do this by developing a Loran accuracy model and considering Loran coverage in the US. and Canadian West after the “mid-continent gap” has been filled. We find that cross-rate synchronization would be helpful in general, and especially valuable if a transmitter has failed.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 35, Number 3
Pages:	335 - 346
Cite this article:	Enge, Per K., Noseworthy, Gary, "CROSS-RATE SYNCHRONIZATION OF LORAN-C USING GPS", NAVIGATION: Journal of The Institute of Navigation, Vol. 35, No. 3, Fall 1988, pp. 335-346.
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