Loran Additional Secondary Factor Correction Study for Aviation

G.Linn Roth, David Diggel, Mitchell J. Narins

Abstract:	As a part of the ongoing FAA evaluation to determine if an enhanced or eLoran system can meet required navigation performance (RNP) accuracy standards of 0.3 nmiles, Locus developed a system to generate Loran additional secondary factor (ASF) corrections at individual airports and to apply those ASF corrections in real time during flight trials at those airports. ASF corrections are used to compensate for Loran propagation delays due to variations in ground conductivity, which are the largest source of Loran accuracy errors. The Avionics Engineering Center (AEC) developed a data collection system that operated within its King Air C- 90SE Twin Turboprop and simultaneously recorded data from a 12 channel GPS/WAAS receiver and an all-inview SatMate 1030 eLoran receiver. The recording setup enabled logging of real-time ASF corrected Loran data and uncorrected Loran data, so ASFs developed on different dates could be post-processed using a software utility provided by Locus. In addition, Locus’ ASF flashcard system enables use of various ASF corrections derived at different times and locations during actual flight trials. Flight tests in a number of areas within the CONUS were performed by AEC and subsequently analyzed by Locus. Results indicate that eLoran can easily meet RNP 0.3 accuracy requirements, and that it is likely a single set of ASFs can be used for most airports throughout the year. This program represents an important first step in the establishment of a national ASF database that will be required to develop eLoran operational procedures and standards for aviation.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1771 - 1776
Cite this article:	Roth, G.Linn, Diggel, David, Narins, Mitchell J., "Loran Additional Secondary Factor Correction Study for Aviation," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1771-1776.
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