e-Navigation is the harmonised collection, integration, exchange, presentation and analysis of maritime information onboard and ashore by electronic means to enhance berth to berth navigation and related services, for safety and security at sea and protection of the marine environment.' This is the definition¹ of e- Navigation as adopted recently by the International Maritime Organization. It is a concept to bring together all the various electronic systems, onboard and ashore, to provide a safer marine environment.

But what has e-Navigation to do with eLoran? While Global Navigation Satellite Systems (GNSS) are used by everybody today, the General Lighthouse Authorities' (GLA's) document 2020 The Vision² expressed concerns about the vulnerability of GNSS. The GLA Radio Navigation Plan³ states that 'the provision of a complementary, terrestrial radio navigation service is essential to support e- Navigation.... There is only one candidate: eLoran'. The International Loran Association definition document⁴ notes: 'Enhanced Loran is an internationally standardized positioning, navigation, and timing service for use by many modes of transport and in other applications. It is the latest in the long-standing and proven series of lowfrequency, LOng-RAnge Navigation (LORAN) systems, one that takes full advantage of 21st century technology.

The definition document goes on to state that this latest version of Loran will meet the requirements for maritime, land, and aviation users as well as being a precise source of time and frequency. The reference to time and frequency may come as a surprise to some: what has this got to do with navigation? From the very start of navigation, time has been a critical factor. The importance of this is well known in the story of the Harrison clocks in the early eighteenth century. Today accurate time is essential for the operation of mobile telephone networks, the internet, electricity distribution, and a host of other applications. Modern commerce relies heavily on these applications and without an accurate source of timing, commerce would grind to a halt.

eLoran can provide a highly accurate time and frequency source, as well as providing better than 10m accuracy for positioning and navigation.

So how does eLoran differ from Loran-C? The transmitters and masts are essentially the same but the use of modern components ensures a more reliable and steady signal. Differential techniques to overcome offsets, and seasonal and daily changes, will be used for those areas requiring higher accuracy, such as the major ports for maritime users. A data channel, built into the signal, will provide additional information to modern receivers. And those receivers are likely to be integrated with GNSS receivers so a user may not know what system is being used to allow their continued safe navigation. Loran stations in the former Northwest Europe Loran System already have many of the components for eLoran, as their stations are equipped with solid state transmitters, uninterruptible power supplies, caesium clocks and have a modern timing and control system in place.

The GLA trials of Loran from Rugby successfully proved a number of concepts and a 15 year contract was awarded to VT Communications in May 2007 for the provision of an eLoran service from their site at Anthorn in Cumbria⁵.

However, there remains a problem with coverage across Ireland and Western Europe. The idea of a mini- Loran station in the west of Ireland has been suggested to improve coverage, possibly using existing infrastructure, for example a former Decca Navigator site.

A decision on the future of Loran in the United States is expected by the end of 2007 and may have been reached by the time this article is published. It is widely expected that the decision will be positive and will propose that eLoran is implemented at all 24 US stations. A European Radio Navigation Plan is expected to be published in 2008 in the form of a communiqué with appendices and is also expected to be positive towards eLoran. There are on-going delays in the implementation of Galileo, the European GNSS, (which suffers from similar vulnerabilities to GPS and cannot therefore be considered a back-up to GPS). The cost of a European eLoran system would be a fraction of the cost of Galileo.

The history of Loran in recent times has been up and down but the days of sole means navigation (using only a single system or method) should be long gone. The need for a complementary system to GNSS is well recognised by a diverse range of radionavigation communities. There is a system able to fulfil this role in a very cost effective way. Much of the infrastructure is in place for such a system. Decisions are expected soon in favour of that system.

And that system is eLoran, at last coming back to the future.

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