Development and Status of Integrated GPS/Loran Prototype for Aviation

G. Linn Roth, James L. Davis and Mitchell J. Narins

Abstract:	For the last several years, the FAA has been performing an evaluation of a modernized, or “enhanced” Loran (e- Loran) system to determine if it can meet FAA requirements for accuracy, availability, continuity and integrity that accord with required navigation performance (RNP) specifications of 0.3 nmi for nonprecision approach (NPA). As a part of this program, Locus, Inc. and FreeFlight Systems have worked to develop an integrated GPS/Loran prototype system using Locus’ all-in-view SatMate 1030 Loran receiver and FreeFlight’s 2101 Approach Plus GPS/WAAS navigation system, and to perform flight trials on the combined units in cooperation with the Avionics Engineering Center of Ohio University. In the first phase of this program, Locus developed automated Loran station selection software and real-time additional secondary factor (ASF) correction capabilities on its SatMate 1030 receiver to enhance Loran accuracy, and integrated FreeFlight’s GPS antenna and Locus’ Hfield Loran antenna in an ADF radome for flight-testing. FreeFlight modified the 2101 to provide front-panel GPS/Loran control and accept SatMate data, and added vertical and horizontal course deviation indicators (CDI) comparing GPS and Loran. Flight tests on this first, twounit prototype system showed Loran accuracy well within RNP 0.3. The second phase of this program is ongoing, and FreeFlight and Locus are working on a single unit prototype and performing additional GPS/Loran integration. Locus is designing a special power supply and interface board to permit operation of the SatMate 1030 using the same power supply as the 2101 Approach Plus, and FreeFlight is developing software to display GPS/WAAS and Loran information and allow analysis of accuracy and integrity models. The prototype GPS/WAAS/Loran system will be housed in a single enclosure that uses a Dzus-mount rail system commonly used for avionics. In addition, Locus is incorporating a single-axis gyroscope into the H-field antenna that further improves receiver performance under dynamic flight conditions. This paper summarizes the GPS/Loran integration efforts and status of this program, and presents flight test results from the GPS/Loran prototype.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	448 - 454
Cite this article:	Roth, G. Linn, Davis, James L., Narins, Mitchell J., "Development and Status of Integrated GPS/Loran Prototype for Aviation," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 448-454.
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