Loran-C is a low frequency/long wave electronic position fixing system using radio signals transmissions @ 100 KHz from 3 or more transmitters, linked in a chain. It gives a latitude and longitude readout position to marine, aero and land receivers. It is transmitted via a vertical mast. The proposed mast at Loop Head is a key element of the Civil Northwest European Loran-C System.

Similar radio transmissions include:

It is a vertical, triangular, latticed mast of uniform width. It comprises of 3 vertical uprights, arranged as an equilateral triangle. Each side is 1.7m (5.5 ft). The vertical poles are 90mm (3.5") in diameter. They are joined by bracing stays which are 40mm (1.6") wide. The mast is supported with wire stays. It is 219 m ( 720 ft) in height. It is very similar to the Radio Tara mast in Co. Meath, which is taller (804 ft) and of heavier construction.

Ireland, along with France, the Netherlands, Denmark, Norway and Germany signed an International Agreement for the establishment and operation of a civil Loran-C navigational system in North West Europe (NELS) on 6th August 1992 in Oslo. This agreement was signed by the Fianna Fail/Progressive Democrat government of the time. The agreement was ratified by the Dail on 8th October 1992.

There were discussions with all marine and safety organisations.

An Environmental Impact Statement (EIS) was furnished at the public library in Kilkee, Loop Head Lighthouse and the Town Hall, Ennis.

A circular informational letter was sent to all Loop residents in February 1993. There were public meetings in Cross and Kilkee, Co. Clare, in 1993. Clare County Council rejected planning permission but An Bord Pleanala granted permission to proceed on 4th November 1994 after an appeal. There was a nine day oral hearing in Ennis in June 1994 as part of the appeal process.

Two Court cases were undertaken by anti-Loran-C interests. 

1.  That Irish Lights were acting outside their powers (ultra vires) in the 1894 Merchant Shipping Act in classing the Loran-C mast as a beacon.

The Supreme Court upheld this view on 18th July

Legislation passed by the Dáil on 18th February 1997 reaffirming C.I.L. powers. 

2.  Bord Pleanala were challenged on their powers to grant planning permission. On 6th December 1996, the High Court upheld Bord Pleanala powers:

To take into account the Dáil decision on the NELS Agreement.

The common good as envisaged by the Government when they signed the International Agreement.

This decision was appealed to the Supreme Court. On the 22nd of April 1998 the Supreme Court upheld the High Court decision.　

Within Europe the E.U. promotes the development of Loran-C chains. The most recent draft European Radio Navigation Plan (ERNP) and European Commission report (31/10/96) includes Loran-C as part of the desired system mix in marine, land transport and aviation to at least the year 2020. In the same report, it is intended to close Decca down in Europe in 1999. Norway closed down their 5 Decca chains and associated stations on 17th January 1997. The GLAs as operators of the Decca system in Britain have announced that their service will cease by the end of March 2000.

Satellite navigation systems (GPS and GLONASS) can fairly be described as the prime navigational systems and the systems for the future. However, it is expensive, it is under military control, and is in the control of a single country (GPS - USA, GLONASS - CIS). Neither system meets integrity requirements for civil users. There is integrity monitoring but it is not real time. (i.e. The user is only told of the error later.)

A European civil satellite system (Global Navigation Satellite System - GNSS2) is not considered viable until the year 2015, if at all. Present costs are estimated at 60 billion dollars. Consequently many countries around the world have implemented or are implementing Loran-C as a back-up or complementary service and as an integrity check to satellite navigation systems in the event of their deliberate or inadvertent failure. Receiver failure when relying on a single system must also be considered.

GNSS1 in Europe is the augmentation of GPS and is presently being tested. This is known as EGNOS - European Geostationary Overlay Service. It is the use of commercial geostationary satellites such as Inmarsat to provide integrity and differential corrections to the raw GPS signal and transmit these corrected signals. The basis for this augmentation depends on the continued provision of the GPS signal. The system is not expected to be operational until after year 2003.

Decca has been discontinued in the UK and Ireland. There are four Decca masts in the Republic of Ireland. There are 24 masts in Britain and Ireland at average height of 300 ft. However, Decca suffers in range, accuracy, night effect and cost compared to Loran-C. There is poor coverage on the South Coast of Ireland with errors rated in miles. Decca requires many more masts than a Loran-C system. One Loran-C mast will suffice for total U.K. and Ireland coverage. The Decca service in the UK ceased operation from 31st March 2000. The Irish Decca stations ceased operation on May 19th 2000.

Yes. In Europe there is The Civil Northwest European Loran-C system, NELS (8 transmitters, 4 chains - Loop Head is not operational). In the Mediterranean the Italians (2) and Spanish (1 Estartit) operate 3 stations on request. There is a transmitter in Turkey which may be rebuilt which is part of the Spanish and Italian systems. In the Far East, Japan, China, Korea and Russia have joined a Loran-C consortium (FERNS). Russia operates the Chayka system, compatible with Loran-C. There are also chains in India and Saudi Arabia. All of the continental USA and Canada is covered by a series of chains.

• It is under civil control.
• The signal is not deliberately degraded.
• Signals can be received in cities and mountainous areas where GPS cannot reliably penetrate.
• Loran-C has the ability to warn users of defects or loss of integrity in the system in real time (guaranteed within 10 seconds). GPS does not do this in real time (11/2 to 4 hour delay).
• The repeatable accuracy of the navigational fix is good.
• Capital and operational costs are a fraction of satellite costs.
• Loran-C may be used to supply long range differential corrections to GPS.

(N/B 13/2/97 Mariners are continued to be reminded by the U.K. Hydrographer that GPS is not approved as an aid to primary navigation and does not have the required integrity for precise navigation, particularly in coastal waters.)

The overall capital costs for NELS is $31.5 million for the six participating countries. The contributing percentage costs are:

The McManus Report investigated public health regarding radiation from a transmitting mast such as the proposed Loop Head Loran-C. The power output is no greater than that of a typical RTE or BBC station. Aside from precautions to be taken by maintenance personnel servicing the mast and limiting public access, there have been no identifiable risks for public health. A quote from the McManus Report - "it has not been possible to identify any grounds for supporting a belief that the operation of the proposed Loran-C transmitter at Loop Head presents a hazard to health"

Loop Head Loran-C transmits at average power 8kw - peak 250kw. Proportion 1:8.

Atlantic 252 transmits at 500kw continuous output.

RTE, Tullamore, transmits at 500kw continuous output.

BBC Radio 4 transmits at 400kw continuous output.

Loran-C was initially an American Department of Defence system covering the Pacific and Atlantic areas for 20 years. In 1974 the system was opened up to civil use. Because the U.S.A. has functional control of G.P.S., Congress decided they had no need to support two independent overseas marine systems. As a result, all overseas stations were closed down or handed over to host states to operate in 1993.

North American Continental Loran-C systems are in situ and are being maintained. Continental USA coverage has been expanded for land and aviation use. On 1.1.95 a combined Russian/American chain was opened to cover the Bering Sea. There are proposals to close American Loran-C stations in year 2000. Congress is examining this proposal. There is considerable consumer resistance to the proposal due to the amount of receivers in use and the necessity to change to GPS receivers. A recent Report of the President's Commission on Critical Infrastructure Protection voiced concerns on relying solely on satellite navigation. The DOT has commissioned Booz Allen and Hamilton to undertake a study on the consequences of de-commissioning Loran-C in the USA.

Yes. Loran-C is a passive system available to anyone with a receiver. When surfaced submarines can receive any uncoded signal such as GPS, Glonass, Loran-C, Decca, Radiobeacons. They can also use these systems when submerged by deploying an aerial to the surface. While on the surface they can also use visual marks to determine their position.

In the same way, all aircraft, including military aircraft, may use civil aero directional radiobeacons for their navigation.

Submarines probably also have access to other secret military satellite systems launched by their own governments.

A submarine's prime positional system is by ship's inertial navigation system (SINS) allied to sonar-echo sounder mapping when submerged. The "Red October" film depiction is very accurate. As Loran-C is dependent on the measurement of the speed of radio waves through air, penetrating a different medium such as water will degrade the positional information.

It was manufactured in France in disassembled sections and is stored there.