Low Frequency (LF) Solutions for Alternative Positioning, Navigation, Timing, and Data (APNT&D) and Associated Receiver Technology

A. Helwig, G. Offermans, C. Schue, B. Walker, T. Hardy, K. Zwicker

Abstract:	Many government and civilian organizations around the world are studying the problem of what to do when Global Navigation Satellite System (GNSS) based services are unavailable to provide Positioning, Navigation, Timing, and Data (PNT&D) information to public and private sector users. There is a general concern about the over-reliance on GNSS which is susceptible to degradation, outages, and unavailability, whether intentional or unintentional, and which operates in many cases without an additional system to provide Position, Navigation and Time (PNT)information for validation and backup. Two recent examples are cited below. In May 2010, the International Civil Aviation Organization(ICAO) Navigation Systems Panel (NSP) working group developed a flimsy documenting “work being accomplished by the U.S. Federal Aviation Administration(FAA) to assess alternatives for providing PNT services when GNSSis not available due to RFI.” [1] During an FAA APNT public meeting in August 2010, UrsaNav and Nautel recommended the FAA consider a Low-Frequency (LF) Alternative Positioning, Navigation, and Timing (APNT) solution to maintain safety and minimize economic impacts from GNSS interference outages. [2] During the 49th International Association of Marine Aids to Navigation and Lighthouse Authority (IALA) Council Meeting, a side question was directed to Industrial Members as to what industry is working on or thinking about regarding the ever increasing reliance on GNSS-based navigation systems. There is a growing concern in the marine community that mariners are losing the basic knowledge and skills needed to navigate by other means and becoming too reliant on satellite technologies. It was noted that coastal navigation maintains traditional aids to navigation, such as, buoy, beacons, and racons, but with the planned removal of some Loran stations and other longer range tools, there is a lack of redundant aids for deep sea navigation. [3] The council recommended that “IALA should encourage the development of a global redundant system, or combination of systems, independent and dissimilar to GNSS, to facilitate e-Navigation.” [4] The FAA Working Group Meetings report to ICAO [1] provided three recommendations, none of which included a LF alternative. In this paper we present our research and findings and propose LF solutions that either can meet FAA’s APNT requirements independently, or support them by providing key solutions to widespread dissemination of time and/or data over a wide area. Since our proposed LF solutions meet the strict FAA requirements, they will most likely also meet the requirements from other modes (e.g., time and frequency, maritime, land-based, and mobile). We also include our research on the associated broadcast and reception technology. Our proposed solutions can maintain safety and minimize economic impacts from GNSS interference outages. All of the proposed solutions have a data capability that can be fine-tuned to a specific need. Our current efforts expand on several years of work in LF PNT&D systems, including the development of a small footprint LF system that is cost-effective, rapidly deployable,and easily transportable. Our solutions are technologically-advanced and provide low-cost alternatives that lessen the dependence on GNSS.
Published in:	Proceedings of the 2011 International Technical Meeting of The Institute of Navigation January 24 - 26, 2011 Catamaran Resort Hotel San Diego, CA
Pages:	206 - 222
Cite this article:	Helwig, A., Offermans, G., Schue, C., Walker, B., Hardy, T., Zwicker, K., "Low Frequency (LF) Solutions for Alternative Positioning, Navigation, Timing, and Data (APNT&D) and Associated Receiver Technology," Proceedings of the 2011 International Technical Meeting of The Institute of Navigation, San Diego, CA, January 2011, pp. 206-222.
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