ACCURACY PERFORMANCE OF ELORAN FOR MARITIME APPLICATIONS

Jan Safar, Kebasenotse Caspar Lebekwe, Paul Williams

Research output: Contribution to journalArticle

Abstract

E-Loran, or enhanced Loran, is the latest in the longstanding and proven series of low fre-
quency, LOng-RAnge Navigation systems. eLoran evolved from Loran-C in response to the
2001 Volpe Report on GPS vulnerability. It improves upon previous Loran systems with
updated equipment, signals, and operating procedures. The improvements allow eLoran to
provide better performance and additional services when compared to Loran-C, and enable
eLoran to serve as a backup to satellite navigation in many important applications.
Different applications impose specific requirements on the navigation system’s accuracy,
availability, integrity and continuity performance. In the maritime sector, accuracy require-
ments are the most stringent. In order to comply with the requirements of the International
Maritime Organisation (IMO) for harbour entrance approach, eLoran has to provide an accuracy
of better than 10 m (95%).Achieving this target is possible if the eLoran navigation receiver is equipped with an up-to-date
database of signal propagation corrections and if real-time differential Loran corrections are
applied. When these conditions are met, the achievable accuracy is largely determined by the
transmitters’ geometry, signal strengths and atmospheric noise levels, but also by the mutual
interference among eLoran stations. This is also referred to as Cross-Rate Interference (CRI)
and is inherent to the way all Loran systems operate.
In this paper we present results of the eLoran research that is being conducted at the Czech
Technical University in Prague (CTU) and the University of Bath (UK) in cooperation with
the General Lighthouse Authorities of the United Kingdom and Ireland. In our work we have
focused on questions that arise when considering introducing new eLoran stations into an
existing network. This particular paper investigates the achievable accuracy performance of
eLoran for maritime applications. The sources of measurement error in eLoran are reviewed,
and an eLoran accuracy performance model is presented. Special attention is paid to the
problem of CRI and possible ways of its mitigation.
Original languageEnglish
Pages (from-to)109-121
JournalAnnual of Navigation
Volume16
Publication statusPublished - 2010

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