Coverage of a Radiobeacon-Based Differential GPS Network

Per K. Enge, Michael F. Ruane, Diane Langlais

Abstract:	A radiobeacon-based system is being developed by the U.S. Coast Guard for the communication of differential GPS (DGPS) messages. :rhis system adds a digitally modulated subcarrier to transmissions from existing marine radiobeacons, which operate in the 285kHz to 325kHz band. The idea is attractive, because a well located and widespread radiobeacon network is already in place. Additionally, the DGPS/radiobeacon signal can be designed such that it does not interfere with the direction finders which normally use the radiobeacon. Finally, the signal can be reliably received at appreciable distances, because error correcting codes and interleaving are used. In fact, this paper discusses the prediction of DGPS/radiobeacon signal coverage. Several coverage charts are presented as examples. The paper also lists which major U.S. harbors (8 million tons of cargo per year or more) can and cannot be covered if the DGPS subcarrier is installed on existing, continous-broa.dcaat radiobeacons. The achievable signal coverage depends: on which error correcting code is used, and the paper analyzes coverage for a "rate 1/2"' code and a "rate 1/8" code.
Published in:	Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987) June 23 - 25, 1987 Dayton, Ohio
Pages:	70 - 77
Cite this article:	Enge, Per K., Ruane, Michael F., Langlais, Diane, "Coverage of a Radiobeacon-Based Differential GPS Network," Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987), Dayton, Ohio, June 1987, pp. 70-77.
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