• NAVTEX - general introduction
• NAVTEX stations in the UK and the Republic of Ireland
• Notes on the development of the NAVTEX service in the United Kingdom
• NAVTEX becomes an integral part of the GMDSS
• Format of NAVTEX messages
• National NAVTEX serices on 490 kHz
• Reception of NAVTEX broadcasts
• Abbreviations which may be used in NAVTEX broadcasts
• Further information and links
• Information before setting out on a voyage

• Table 1: NAVTEX stations in the UK and Republic of Ireland
• Table 2: Summary of NAVTEX broadcasts on 518 kHz in waters around the British Isles
• Table 3: Subject content of message as defined by the B2 character
• Table 4: Summary of the current UK National NAVTEX broadcasts on 490 kHz
• Table 5: The Met Office Inshore Waters forecast areas included in each of the UK NAVTEX transmissions

NAVTEX is an international automated direct printing service for the promulgation of Marine Safety Information (MSI) to ships at sea. It is an integral part of the Global Maritime Distress and Safety System (GMDSS) and provides a low-cost system in coastal waters, a system that can provide all the safety information required whether on a Merchant ship or on a small craft. The simplest form of receiver incorporates a small printer which prints the output on a small roll of paper, but many units are now available at low cost which store the information in soft copy for access as and when required. The international system operates world-wide on a frequency of 518 kHz so there is no requirement for retuning of the receiver. The output on 518 kHz is in the English language no matter which part of the world the information is being received. The basic receiver can be programmed to receive specific transmitting stations and certain classes of messages, or more to the point, certain classes of messages cannot be programmed out. Messages which cannot be programmed out include distress messages, search and rescue messages, navigational warnings and meteorological warnings (in this context note that meteorological forecasts other than warnings can be programmed out - see below for more on this topic).

The service has been so successful that several countries are now taking up the option of using the national frequency of 490 kHz for the dissemination of additional information such as forecasts for inshore waters and the promulgation of MSI information in the National language. Such information is of particular interest to small craft although it should be remembered that the output on the 518 kHz frequency is the source of essential Marine Safety Information (MSI) for all classes of vessel.

Vessels obliged to carry NAVTEX equipment within the GMDSS regulations must have the receiver switched on and tuned to the 518 kHz frequency continuously, and if access to the new national frequency is required then a second receiver is required. On a vessel which is not required by the SOLAS regulations to carry NAVTEX equipment, it is feasible to have a receiver that can only receive one frequency at any one time. The user can switch to the national frequency of 490 kHz for reception of a bulletin and then switch back to the 518 kHz frequency when the bulletin has been received. This is possible since the NAVTEX station that one will be using will have different time slots for input into the 518 kHz and the 490 kHz service. Vessels that are required to carry NAVTEX equipment by the SOLAS regulations must carry a dual frequency receiver if reception on 490 kHz is required since availability to receive messages on 518 kHz must be maintained at all times.

NAVTEX transmissions are, in general, routine broadcasts within an allocated slot time of ten minutes every four hours. However, urgent information, distress information, warnings of gales etc can be inserted into the system at any time although the NAVTEX operator will ensure that the non-routine transmission is not made at the same time as a neighbouring NAVTEX routine transmission is broadcast (the result of such an action would be that both transmissions would corrupt each other). Also it is worth noting that any warning issued at a non routine time is repeated in the following scheduled ten-minute slot.

NAVTEX services in English on 518 kHz are now available in all coastal waters of Europe and in many other parts of the world so that worldwide vessels have access to marine safety information in English via the medium of NAVTEX.

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NAVTEX stations in the UK and the Republic of Ireland

The following notes summarise some aspects of the service available in waters around the United Kingdom and the Republic of Ireland and that provided by Norway, Belgium and France for the North Sea and South-west Approaches to the British Isles. Details of the location of the three stations providing a service in the United Kingdom and the two stations in the Republic of Ireland are listed below.

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Development of the NAVTEX service in the United Kingdom
      (based mainly on information in The Marine Observer, — a journal produced quarterly by the Met Office and published by The Stationery Office

NAVTEX is an acronym for NAVigational TEXt messages. The technology for the dissemination of these text messages via a simple radio-telex system has been about for some considerable time, certainly since the late 1970s when the Post Office Coastal Radio Station at Cullercoats in the north-east of England commenced broadcasting weather forecasts and gale warnings for the North Sea and most of the English Channel shipping forecast areas from Fair Isle to Plymouth on what was then referred to as a temporary radio teletype broadcast. Apart from a change of name from the Post Office Coastal Radio Station Cullercoats, to British Telecom International Coastal Radio Station Cullercoats in the early 1980s the temporary service continued with reports coming in of its success. In April 1983 the service was declared as an operational service alongside those provided via the conventional means of the MF Morse broadcasts and those via the marine radio-telephony service.

On 1st October 1983 the service was extended to the BT coastal radio station at Portpatrick. The weather information broadcast from Portpatrick included forecasts and a gale-warning service for the western sea areas of the UK, including Fair Isle in the north and all the western coastal sea areas from Lundy in the south to South-east Iceland in the north.

During 1985, NAVTEX broadcasts were started via Land End Radio. This broadcast included warnings and forecasts for the English Channel, the Irish Sea and all the sea areas in the South-west Approaches included in the main shipping forecast. However, reports suggested that the site at Lands End was not ideal for the intended area of coverage, and so the NAVTEX facility at Lands End was moved about a year later, in 1986, to the BT International coastal radio station at Niton on the Isle of Wight.

By 1987, interest in NAVTEX was growing and NAVTEX services were being successively introduced in other countries. The author of these notes does not have information as to how much MSI other than the meteorological bulletins was included in the transmissions in those early years, but gradually all the operational MSI information broadcast by W/T and R/T was incorporated into the bulletins. Procedures applicable to stations transmitting NAVTEX information on the frequency of 518 kHz were given in Article 14A of the Radio Regulations and in Resolution No.324 (Mob-87) of the World Administrative Radio Conference for the Mobile Services, 1987. Following the sixty-third session of the Maritime Safety Committee (May 1994) a second edition of the NAVTEX Manual was produced and this continues to be the basis on which the NAVTEX service operates today.

NAVTEX was a part of the marine communications organisation for shipping run by the Post Office and afterwards by BT International. The services included the broadcast of gale warnings, weather forecasts and navigational warnings both via the medium of W/T and R/T as well as via the NAVTEX service. The network of Post Office stations also dealt with distress traffic, telegrams to and from ships and enabled link telephone calls to be made from ships at sea to land subscribers world-wide. In the latter years of the operation of the coastal network of marine radio stations by BT International the UK NAVTEX service via all three transmitters was co-ordinated at Stonehaven Radio (not at one of the transmitting centres). It was to Stonehaven Radio that all the meteorological texts were sent from the Meteorological Office and other MSI information from the sources of that information such as the Hydrographic Office for broadcast via the UK NAVTEX service.

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NAVTEX becomes an integral part of the GMDSS

NAVTEX was incorporated into the new regulations for the system known as the Global Maritime Distress and Safety System (GMDSS). This system underwent a transitional phase from 1 February 1992 until 1st February 1999 from which date the GMDSS requirements became mandatory within Chapter V of the Convention for Safety of Life at Sea (SOLAS). From 1st August 1993 all vessels bound by the requirements of the SOLAS Convention have been required to carry NAVTEX equipment even though NAVTEX transmissions were by no means available world-wide.

On the 1st July 1999 BT International began to hand over the responsibility for dissemination of Marine Safety Information (including the provision of weather forecasts and warnings) to the Maritime and Coastguard Agency (MCA). This responsibility included the provision of MSI information to ships at sea via the medium of the HM Coastguard VHF and MF stations Early the following year, on the 1st February 2000 the MCA took over the responsibility for the transmission of the UK NAVTEX service. Control of the service was moved from Stonehaven to the MRCC (Maritime Rescue Co-ordination Centre) at Falmouth. It was shortly after this, on the 30 April 2000 that the BT HF station at Portishead ceased operations with the main source of safety information for ships in NAVAREA ONE on the North Atlantic outside of NAVTEX coverage being the Inmarsat SafetyNET™ service. The two Irish NAVTEX stations, Malin Head and Valentia, became operational later in 2000, the service via those stations being maintained by the Irish Coastguard and extended the availability of the provision of MSI via NAVTEX from 15°W to 20°W.

The set of sea areas for which forecasts and gale warnings were broadcast by the three UK NAVTEX stations was based on the station locations at Cullercoats, Lands End and Portpatrick and these groupings of areas persisted until November 2000 when a rationalisation of the sea areas to be included in each transmission was introduced, For example, the areas Irish Sea, Rockall and Malin were relevant in a broadcast from Lands End but not in a broadcast from Niton. Also courtesy the Irish Coastguard the two stations in the Republic of Ireland were able to take on the responsibility of broadcasting warnings and weather forecasts for users of the NAVTEX service out to 20°W. Thus several of the sea areas around the north, south and west of Ireland together with parts of the High Seas forecast for Metarea I are included in the transmissions from Malin Head and Valentia.

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Format of NAVTEX messages

All broadcasts on 518 kHz are in English (International requirement). Broadcasts on 490 kHz may be in English, but more likely in the national language of the country providing the broadcast. For example, all NAVTEX stations in France broadcasting on 490 kHz are in the French language.

Heading B1B2nn

Every NAVTEX message has information within the message header, for example EE45 indicates that the message is transmitted from Niton [E], and the Message is a meteorological forecast (E). Thus the heading indicates which NAVTEX station broadcasts it, the type of information and a sequential number of the message. This information enables the receiver to be programmed to print/store a message just once on its receipt the first time into the NAVTEX receiver. Thereafter a message with the same B1B2nn heading will not be printed or held in store again in the receiver as long as it is not switched off. The format of the heading makes it possible to program one's receiver to accept or reject various classes of messages and also prevents the printing of the same message over and over again.

B1 denotes the broadcast (station and time of routine transmissions), for example E indicates Niton using the slot time of 0040 and every four hours thereafter.

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The B2 character character (see Table 3) denotes the subject matter of message which follows, 'E' for example, indicates that the message is a Meteorological forecast. The heading also contains the serial number nn of the message inserted by the originator. For example, all forecasts provided by the Met Office and broadcast via Niton have the heading EEnn. See Table 3 below for the decode of the character B2.

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On a standard NAVTEX receiver compatible for use within the GMDSS regulations it should not be possible to reject messages with a B₂ character A (Navigational warnings), B (meteorological warnings) and D (Search and rescue information), but note that although category L can be programmed out, in UK waters this category should programmed so that messages are accepted since this indicator is used by the UK to provide messages such as GUNFACTS and SUBFACTS etc, information which may be of interest to small craft.

For those wishing to receive forecasts as well as Meteorological warnings it should be noted that it is possible to programme out receiving the Meteorological forecast texts (E). Thus if forecasts are required as well as warnings then ensure that messages with category of E are not programmed out.

When programming the receiver it is wise to ensure that only those transmitters which are required are programmed for reception otherwise a good deal of paper will be wasted or one will have to scroll through a mass of messages if the broadcasts are received in soft copy. Thus if one is sailing in the English Channel and marine safety information is required for the English Channel and the South-west Approaches and the Bay of Biscay is sought, then it would be wise to programme the receiver to receive Niton [E], Niton [K], and Cross Corsen [A] in Brittany. If sailing on towards the south of Ireland then Valentia [W] should be included once west of Scilly. It would also be useful to retune temporarily to the 490 kHz service provided by Niton [I] for the Inshore Waters forecast at 0520 and 1720UTC (note if retuning it is wise to retune well ahead of the broadcast time in order to ensure that one does not miss the start of the broadcast) and to remember to retune back to 518 kHz as soon as possible after the transmission on 490 kHz has been received. Similar comments apply when sailing in other NAVTEX areas.

Several countries are taking up the availability of the 490 kHz frequency for the provision of a national NAVTEX service with information in the national language and also additional information for small craft not classed as MSI in the context of the broadcasts on 518 kHz. See Table 4 for details of the broadcasts from the three UK stations on 490 kHz.

The 16-area Inshore Waters Forecast, commissioned by the MCA, is available via the National NAVTEX service on 490 kHz and on the Met Office web site. The text consists of a 24-hour forecast for a sub-set of the sixteen areas which are relevant to the area of reception of each of the NAVTEX transmitters (see Table 5 below). A general three-day outlook for all areas is added at the end of the text

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Reception of NAVTEX broadcasts

It is worthwhile remembering that NAVTEX is a medium-wave transmission and a decent aerial is required. Also signal strength in harbours and in some near coastal areas such as in bays and inlets may be very poor. This is obviously a problem when sailing near the coast of Western Scotland were the broadcast from Portpatrick is difficult to receive in many inshore areas.

Abbreviations used in NAVTEX broadcasts

It is estimated that significant savings in the content of NAVTEX broadcasts can be achieved by the use of a standard set of abbreviations. With this in mind the Second Session of JCOMM (Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology) held in Halifax, Canada (19 to 27 September 2005) recommended the use of an internationally agreed list of abbreviations to shorten the texts broadcast within the International NAVTEX service. The table (Annex 2 to the Recommendation) is reproduced below and presented in a decode format.

Abbreviations for wind direction

Decode for abbreviations which may be used in NAVTEX messages for terms other than wind direction
(Note the list has been arranged as decode and is in alphabetical order of the abbreviation)

Both the Shipping Forecast and the 16-area Inshore Waters Forecast are available on the Met Office web site. From the home page, navigate first to Leisure and then to Marine to access the links for the forecasts. Or one can access the Maritime and Coastguard Agency site and click on the Met Office logo on the home page. The forecasts can then be accessed from the resulting page which includes some background to the forecasts.

The gale warning service plus the twice-a-day Shipping Forecasts via the NAVTEX service on 518 kHz provides a complete service of meteorological forecast information to the mariner at sea. Each forecast bulletin includes a list of the areas for which gale warnings are in force, a general synopsis, and forecasts for each sea area (areas being grouped when convenient). Amendments to the forecasts between the routine issues is via the gale-warning service.

For those sailing within 12 miles of the coast the National NAVTEX service on 490 kHz provides the relevant text of the inshore waters forecast. This includes a 24-hour forecast and a 24-hour outlook for each individual inshore area plus a general outlook for all UK inshore waters for the following three days (see Table 5 above). This forecast service on the UK National NAVTEX service on 490 kHz also includes Strong Wind warnings (warnings issued for expectancy of winds of Force 6 or more in the coastal strip extending to five miles offshore).

Further information and links

• Admiralty List of Radio Signals, Vol.3(1) and Vol.3(2)
• Admiralty Marine Communications: United Kingdom and Mediterranean Edition
• Admiralty Marine Communications: United Kingdom and Baltic Edition

The Maritime and Coastguard Agency site has been updated recently and contains useful information and several useful links from the home page to other related organisations including a page giving with information re the availability of forecasts etc from the the Met Office.

There is more information on a site for small craft owners maintained by Frank Singleton. His pages on NAVTEX contain additional information and some links to other useful sites providing information re NAVTEX.