Forecasting Into The Nineties: The Fast Fourier Method In Loran TD Corrections

A. Chris Daskalakis

Abstract:	This paper presents a breakthrough for the FAA in Loran TD forecasting: the application of Fast Fourier transform methodology to determining TD corrections. Forecasting has played an integral part in the use of Loran in the National Airspace System in standard instrument approach procedures. During the past six years, forecasting has evolved to meet the changing needs and requirements of the FAA and other users. The pioneer forecasting method in 1984 was the prediction algorithm, which evolved from an FAA monitor study. Because of the large amount of data required--two years from four sites for each baseline--another method was needed. The Early Implementation Project (EIP) introduced two new methods of forecasting. The 7-day forecast required only three weeks of historical data, but, with growing numbers of users requiring Loran corrections, distribution was difficult. The 56-day forecast followed, and was distributed every eight weeks with the approach chart publication, but when data was inadequate, due to missing or faulty values, it proved difficult to predict. The Fast Fourier Method is the newest and most accurate method of forecasting to date. This paper outlines the four forecasting techniques, emphasizing the advantages of the Fast Fourier Method over previous methods.
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:	165 - 167
Cite this article:	Daskalakis, A. Chris, "Forecasting Into The Nineties: The Fast Fourier Method In Loran TD Corrections," Proceedings of the 1991 National Technical Meeting of The Institute of Navigation, Phoenix, AZ, January 1991, pp. 165-167.
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