GPS and the Future of Lighthouses
The Satellite Revolution in Navigation
The NAVSTAR Global Positioning System achieved full operational capability in 1995, providing continuous worldwide coverage to any receiver with a clear view of the sky. For the first time in maritime history, a ship anywhere on the ocean could determine its position to within a few metres without taking a star sight, without a radio bearing, without any reference to a landmark or lighthouse. The system was free, reliable, and available to vessels of any size. Its uptake by commercial shipping was rapid; recreational boaters followed within a decade as receivers became small enough to fit in a jacket pocket and cheap enough to buy at a chandler's.
The question this created for lighthouse authorities was obvious. If every ship has satellite navigation that works in daylight, darkness, and thick fog, what purpose does a lighthouse serve? The question was not purely theoretical — it had immediate budgetary implications. Running a network of offshore lighthouse towers, many of them requiring helicopter access and specialist maintenance, is expensive. If the navigational function had been made redundant by GPS, the economic case for continuing to run the towers was weak.
The Case for Redundancy
The argument for retaining lighthouses in the satellite age is primarily an argument about system failure. GPS is not infallible. The signal can be jammed — deliberately, by state or non-state actors equipped with radio-frequency jammers — or spoofed, feeding receivers false position data that displaces the apparent position of a vessel by miles without triggering any alarm. Maritime GPS jamming incidents have been documented in the Black Sea, the eastern Mediterranean, and the waters off the Korean peninsula. In each case, vessels equipped with GPS received plausible but false position data. Several ran aground or came close to doing so before the problem was identified.
Spoofing is particularly difficult to detect with standard GPS receivers. The receiver sees a signal that appears legitimate; it reports a position that is internally consistent and that changes plausibly as the vessel moves. Without an independent check — a visual bearing, a radar fix, a cross-check against another navigation system — the navigator may have no indication that anything is wrong until the soundings change or the land appears in an unexpected position.
The General Lighthouse Authorities of the United Kingdom and Ireland, in evidence to a parliamentary inquiry in 2015, argued that visual aids to navigation provided exactly this independent check. A lighthouse visible from the bridge, identified by its character and bearing, offers a position fix that requires no electronics and cannot be spoofed. The argument was accepted; the inquiry recommended that the network of major lighthouses be maintained.
eLoran and the Backup System
The response to GPS vulnerability in some maritime nations has been to invest in eLoran — an enhanced version of the long-range radio navigation system LORAN-C, which was the dominant electronic navigation method before GPS. eLoran transmits on very low frequencies that are difficult to jam and impossible to spoof in the same way as GPS, because the signals originate from large ground-based transmitters rather than satellites. It provides position accuracy comparable to GPS in coastal waters, though not the metre-level precision achieved by GPS augmented with differential correction.
South Korea, which has experienced repeated GPS jamming from North Korea, invested heavily in eLoran infrastructure in the 2010s. The United Kingdom tested eLoran infrastructure from a station at Anthorn in Cumbria. The United States decommissioned its LORAN-C network in 2010 but subsequently reversed course; studies of eLoran reinstatement were commissioned in the mid-2010s following recognition of GPS vulnerability.
The lighthouse in this context becomes part of a layered navigation system: satellite navigation as the primary method, eLoran as a terrestrial radio backup, visual aids as the final independent check. This layering is already implicit in the safety management systems of commercial vessels, which require navigators to maintain traditional plotting skills and to cross-check electronic fixes against visual observations where possible.
Autonomous Vessels and New Demands
The development of autonomous surface vessels — ships that navigate without a human bridge watch officer — creates a different set of requirements for navigation aids. An autonomous vessel relies on sensor fusion: combining data from multiple sources (GPS, radar, lidar, optical cameras, electronic charts) to maintain awareness of its position and the positions of other objects. Visual navigation aids, including lighthouses, are inputs to this fusion process in the same way that buoys and coastal features are inputs.
For autonomous vessels, a lighthouse serves as a reference object that can be detected optically, correlated with chart data, and used to validate the position solution. The lighthouse becomes, in effect, a calibration point for the autonomous navigation system. Several research programmes exploring autonomous vessel navigation have included lighthouse identification as a component of optical scene recognition — the vessel's camera system needs to recognise a lighthouse tower, read its bearing, and use that bearing to constrain the position estimate.
This use of lighthouses in autonomous navigation was not anticipated when the satellites went up in the 1990s. It suggests that the lighthouse has a future role that is different from its historical one — not as the primary source of navigational information for a human officer, but as one element in a machine-readable coastal information infrastructure.
The Heritage Dimension
Beyond the strictly navigational argument, lighthouses have an economic value as cultural and tourist assets that is increasingly recognised by lighthouse authorities and national heritage bodies. The Fastnet lighthouse off southwest Ireland receives visitors by boat in summer; the lighthouse at Portland Bill in Dorset is one of the most visited visitor attractions on the Dorset coast. In the United States, the National Historic Lighthouse Preservation Act of 2000 created a framework for transferring decommissioned lighthouses to heritage organisations, local governments, and non-profits, acknowledging that these structures had value beyond navigation.
The heritage argument for keeping lighthouses operational, rather than merely preserved, rests on the distinction between a functioning lighthouse and a museum exhibit. An active lighthouse — one whose light still sweeps the sea at night — retains a relationship with its original purpose that a decommissioned structure does not. The light matters to the small-boat sailor who sees it and finds reassurance in it, to the heritage visitor who understands its history, and to the arguments for redundant navigation systems.
Trinity House has moved toward a cost-effective middle ground in which lights are maintained at reduced expense by automation and LED technology, with the towers preserved and opened to visitors where practicable. The Commissioners of Northern Lighthouses have taken a similar approach in Scotland. The Irish Commissioners of Irish Lights have worked with the Heritage Council to assess which stations have sufficient heritage value to justify visitor development.
Active Lights on Active Coasts
The practical case for active lighthouses is strongest where satellite navigation is most vulnerable and where the consequences of failure are most severe. Congested port approaches, narrow straits, rockbound archipelagos: these are the places where a GPS failure or spoofing incident could quickly become catastrophic. They are also, not coincidentally, the places where the traditional lighthouse network is densest.
In the waters around the British Isles, the volume of shipping — commercial, fishing, recreational — is among the highest in the world. The tidal complexity of the approaches to major ports like Southampton, Liverpool, and Bristol makes accurate navigation critical. The lighthouse and buoyage system maintained by Trinity House and the other general lighthouse authorities represents an infrastructure investment whose cost is distributed across shipping as harbour dues, and whose value is realised on the occasions when electronic navigation fails or is compromised.
The answer to whether we still need lighthouses is, in the end, the same answer that applies to any safety-critical backup system: we need it most on the occasions when we think we do not. Open the map shows the current extent of the world's active lighthouse network — a system that has been trimmed, automated, and modernised but that, by the judgement of maritime safety authorities on every coast, has not yet reached the point of redundancy.