Vessel Traffic Systems And The Application Of Loran-C Automatic Dependent Surveillance

James E. Culbertson, Walter N. Dean

Abstract:	Pursuant to the Federal Oil Pollution Liability and Compensation Act of 1990, the U.S. Coast Guard is conducting surveys of U.S. ports to determine and prioritize needs for Vessel Traffic Service (VTS). The survey procedure includes evaluating the nature, volume and frequency of vessel traffic, identifying traffic management problems areas where risk of collisions, spills and damage may exist, and identifying VTS technologies which could be applied to those problems to eliminate or ameliorate vessel traffic conflicts. Although classic VTS designs incorporate radar and television as “independent” sensors, Loran-C and other radio positioning systems are being considered as “dependent” sensors in VI’S designs. While Automatic Dependent Surveillance (ADS) systems require cooperation from the vessel under surveillance, either by choice or by regulation, they extend VTS sensor capability over a much larger area than is economically feasible by other means. The Cook Inlet area, with its nominal volume of marine traffic carrying cargoes that could be injurious to the environment, is a candidate for using ADS as a VTS resource. Loran-C is the most likely radio navigation system to employ because it is, at present, much more available and loran receivers of all types are common. Although coverage from the Gulf of Alaska Loran-C Chain (7960) and the North Pacific Chain (9990) in Cook Inlet may appear marginal on the nautical charts, the printed Time Differences @D’s) do not reflect the fairly recent addition of Port Clarence as the Zulu Secondary for the Gulf of Alaska Chain (7960). Repeatable position errors, stability of positions over time, predictability of loran accuracy and positions errors in Latitude and Longitude are examined for Cook Inlet. Propagation delay errors due to the rugged Alaska terrain are discussed. With suitable one-time calibration of Loran-C in Cook Inlet, time difference corrections as a function of position can be determined. This would permit the effective use of Loran-C ADS for vessel traffic management in Cook Inlet.
Published in:	Proceedings of the 1991 National Technical Meeting of The Institute of Navigation January 22 - 24, 1991 Sheraton San Marcos Hotel Phoenix, AZ
Pages:	135 - 140
Cite this article:	Culbertson, James E., Dean, Walter N., "Vessel Traffic Systems And The Application Of Loran-C Automatic Dependent Surveillance," Proceedings of the 1991 National Technical Meeting of The Institute of Navigation, Phoenix, AZ, January 1991, pp. 135-140.
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