Student : Pavel MirceaGrupa : TA 31Profesor : Pricop Codruta

General Introduction

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 518kHz so there is no requirement for retuning of the receiver. The output on 518kHz 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 490kHz 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 518kHz frequency is the source of essential Marine Safety Information (MSI) forallclasses of vessel.Vesselsobliged to carryNAVTEX equipment within the GMDSS regulations must have the receiver switched on and tuned to the 518kHz 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 490kHz for reception of a bulletin and then switch back to the 518kHz 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 518kHz and the 490kHz service . Vessels that are required to carry NAVTEX equipment by the SOLAS regulations must carry a dual frequency receiver if reception on 490kHz is required since availability to receive messages on 518kHz 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 518kHz 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.

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.

Station Transmitter siteNiton 5035'N 118'WCullercoats 5504'N 128'WPortpatrick 5451'N 507'WMalin Head 5522'N 721'WValentia 5127'N 949'W

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 asa 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 518kHz 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.

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 servicControl 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 15W to 20W. 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

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 20W. 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.

All broadcasts on 518kHz are in English (International requirement). Broadcasts on 490kHz 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 490kHz are in the French language. NAVTEX messages are transmitted using binaryfrequency shift-keying(BFSK) at 100 bit/s and a 170Hz frequency shift. The characters are encoded using the 7-bit CCIR 476 character set and basic error detection is enabled by employingforward error correction(FEC). This is the same format as the SITOR-B (AMTOR) format.A NAVTEX message is built onSITORcollective B-mode and consists of :

a phasing signal of at least ten secondsthe four characters "ZCZC" that identify the end of phasinga single spacefour charactersB1, B2, B3and B4(see below)a carriage return and a line feedthe informationthe four characters "NNNN" to identify the end of informationa carriage return and two line feedseither5 or more seconds of phasing signal and another message starting with "ZCZC"oran end of emission idle signal for at least 2 seconds.

B1is an alpha character identifying the station, and B2is an alpha character used to identify the subject of the message. Receivers use these characters to reject messages from certain stations or if the message contains subjects of no interest to the user.

B3and B4are two-digit numerics identifying individual messages, used by receivers to keep already received messages from being repeated.

For example , a message containingB1B2B3B4characters of 'FE01' from a U.S. NAVTEX Station indicates a weather forecast message from Boston MA.

NAVTEX message example:

(phasing signals >= 10 seconds) ZCZC FE01 (message text ...) NNNN (end of message phasing signals for >= 2 seconds before next message)

Start of messageZCZC begins the message.

Transmitter identity (B1)This character defines the transmitter identity and its associated coverage area.

Subject indicator character (B2)The subject indicator character is used by the receiver to identify different classes of messages below. The indicator is also used to reject messages concerning certain optional subjects which are not required by the ship (e.g.LORANC messages might be rejected in a ship which is not fitted with a LORAN C receiver).

NAVTEX broadcasts use following subject indicator characters : A - Navigational warningsB - Meteorological warningsC - Ice reportsD - Search & rescue information, and pirate warningsE - Meteorological forecasts

F - Pilot service messagesG - AISmessagesH - LORANmessagesI - Not usedJ - SATNAV messages (i.e.GPSorGLONASS)K Other electronic navaid messagesL - Navigational warnings - additional to letter A (Should not be rejected by the receiver) T - Test transmissions (UK only - not official)V - Notice to fishermen (U.S. only - currently not used)W - Environmental (U.S. only - currently not used)X - Special services - allocation byIMONAVTEX PanelY - Special services - allocation byIMONAVTEX PanelZ - No message on hand

Receivers use the B2character to identify messages which, because of their importance, cannotbe rejected (designated by a1). The subject indicator characters B, F and G are normally not used in the United States since theNational Weather Servicenormally includes meteorological warnings in forecast messages. Meteorological warnings are broadcast using the subject indicator character E. U.S. Coast Guard District Broadcast Notices to Mariners affecting ships outside the line of demarcation, and inside the line of demarcation in areas where deep draft vessels operate, use the subject indicator character A.

Time of originThe time of the transmission of the message is in UTC.

On a standard NAVTEX receiver compatible for use within the GMDSS regulations it should not be possible to reject messages with a B2character 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.

Serial number of message (B3, B4)These two characters define the serial number of each B2message type (class). Generally serial numbers start with the numbers '01', however in special circumstances, the numbers begin with '00'. This forces the receiver to print the message.

End of messageThe end of the message is asserted when the characters "NNNN" are received.

NAVTEX Transmission Schedule

Each station identifier has a fixed 10 minute time slot, starting with A at 0000UTC. The time slots are repeated at 4 hour intervals.

Within each time slot, a mix of navigation warnings, weather forecasts, ice information and other content may be sent, and this is normally according to a structured plan for that specific station. For example, in the first and third time slot they may decide to transmit navigation warnings, and weather forecasts in the others. Normally eachNAVAREAor sub-NAVAREA has only one station at each slot.

NAVTEX receivers

NAVTEX receivers which are approved for GMDSS contain an internal printer and/or a scrollable display, and cost between $800$1500. A new generation of NAVTEX receivers intended for non-GMDSS applications such as the recreational community is now entering the marketplace. These receivers include features such asLCDscreens andRS-232output and have a purchase price in the $300$500 range. In the UK they can be purchased for 115. There are also a number of NAVTEX engines available that do not have any user interface, and just output decoded data in RS-232format, either as a simpleASCIIdata stream, or using theNMEANAVTEX sentences, or their own proprietary protocol.

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

Terminology NAVTEX abbreviation

North or Northerly NSouth or Southerly SNortheast or Northeasterly NESouthwest or Southwesterly SWEast or Easterly EWest or Westerly WSoutheast or Southeasterly SENorthwest or Northwaesterly NW

Decode for abbreviations which may be used in NAVTEX messages for terms other than wind direction

Abbreviation Terminology Abbreviation Terminology Abbreviation Terminology BACK Backing KMH Km/h QUAD Quadrant BECMG Becoming KT Knots RPDY Rapidly BLDN Building LAT/LONG Latitude/Longitude SCT Scattered C-FRONTorCFNT Cold front LOC Locally SEVorSVR Severe DECR Decreasing M Metres SHWRSorSH Showeres DPN Deepening MET Meteo....... SIG Significant EXP Expected MOD Moderate SLGTorSLT SlightFCST Forecsat MOVorMVG Moving/Move SLWY Slowly FLN Filling NC No change STNR Stationary FLW Following NM Nautical miles STRG Strong FM From NOSIG No significant change TEMPO Temporarily/Temporary FRQ Frequent/frequency NXT Next TEND Further Outlooks HPA HectoPascal OCNL Ocasionally VEER VeeringHVY Heavy O-FRONTorOFNT Occluded front VIS VisibilityIMPR Improving/Improve POSS Possible VRB VariableINCR Increasing PROB Probability/Probable W-FRONTorWFNT Warm FrontINTSF Intensifying/Intensify QCKY Quickly WKN WeakeningISOL Isolated QSTNR Quasi-stationary

Information availabilityBoth theShipping Forecastand the 16-areaInshore Waters Forecastare available on theMet Office web site. From the home page, navigate first toLeisureand then toMarineto access the links for the forecasts. Or one can access theMaritime and Coastguard Agencysite 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 serviceplusthe twice-a-day Shipping Forecasts via the NAVTEX service on 518kHz 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.

StationE - UK Niton 2013-01-16 21:46:13 (GMT+1) Signal quality 100 Message number09TypeA (Nav warning)

ZCZC EA09 WZ 080 ENGLAND, SOUTH COAST. WESTERN APPROACHES TO THE SOLENT. SW SHINGLES LIGHT-BUOY 50-39.3N 001-37.5W OFF STATION. NNNN

ZCZC EA07 ENGLAND, SOUTH COAST. APPROACHES TO TOR BAY, BERRY HEAD NORTH-EASTWARD. DANGEROUS WRECK REPORTED 50-28.12N 003-24.88W. NNNN

ZCZC EA68 WZ 1634 ENGLISH CHANNEL. HURD DEEP NORTHWARDS. 1. UNMARKED EQUIPMENT ON SEABED IN VICINITY 49-40.8N 003-43.8W. WIDE BERTH REQUESTED. 2. CANCEL WZ 1409 (EA21). NNNN

SOUTHERN NORTH SEA, UK SECTOR. SATURN GAS FIELD. 1. PLATFORM 48/10-ND 53-43.50N 001-53.83E, UNLIT. 2. CANCEL WZ 076 (GA92) NNNNGALE WARNINGS: NONE THE GENERAL SITUATION AT MIDDAY NEW LOW EXP BISCAY 1000 BY MIDDAY TOMORROW 24-HR FCSTS VIKING VRB 3 OR 4, BECMG S 5 AT TIMES. SLT OR MOD. SNOW SHWRS. GOOD, OCNL POOR

ZCZC GA38 WZ 1667 NORTH SEA, UK SECTOR. FRANKLIN GAS FIELD. PLATFORM UNDER CONSTRUCTION 56-57.8N 001-48.1E , ALL NAVAIDS INOPERATIVE. NNNNZCZC JA05 140911 UTC JAN POLISH NAV WARN 009 SOUTHERN BALTIC. POLISH COAST. GEOTECHNICAL SURVEYS ARE IN PROGRESS WITHIN A RADIUS OF 1 M FROM PSN 55-26.5N 018-41.5E BY VESSEL 'ST. BARBAA/J8B2227' VESSELS ARE REQUESTED TO NAVIGATE WITH XTREME CAUTION. NNNN

ZCZC JA02 13800 UTC JAN POLISH NAV WARN 008 SOUTHERN BALTICM POLISH COAST. 15-19 JAN DAILY SINCE 0400-0100 UTC ZONES 6 ARE CLOSED CENTRED IN APPROX PSN 54-37N 016-32E. CANCEL 192330 UTC JAN NNNZCZC KA10 WIGHT - DOVER SAILORS ARE ADVISED THAT UNDERWATER OPERATIONS WILL BE CONDUCTED BY SCIENTIFIC SHIP THALASSA FROM 15 TO 23 JANUARY 2013 IN ENGLISH CHANNEL AND NORTH SEA. WIDE BERTH REQUESTED AND KEEP SHARP LOOK. CANCEL THIS MESSAGE 240800 UTC JAN 13.