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Maritime Safety Information Under the GMDSS (The Global Maritime Distress and Safety System)

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A key component of GMDSS is Maritime Safety Information (MSI), which provides mariners with crucial updates for safe navigation. This article will explore MSI GMDSS, explaining its purpose, the types of information it disseminates, and how it enhances safety at sea.

The Global Maritime Distress and Safety System makes specific requirements with regard to radio equipment, and ships must be able to carry out several different functions, one of which is the ability to TRANSMIT and RECEIVE Maritime Safety Information (MSI).

The Navtex System

Navtex (NAVigational TelEX) is an international telex system and is one of the most important elements of the GMDSS.

The system makes it possible for ships sailing in coastal waters to receive Maritime SafetyNET Service by Inmarsatsafety messages at distances of up to 400 nautical miles offshore, MS (messages can be transmitted by the NAVTEX system via the Inmarsat EGC system, or via short wave (HF) telex narrow band direct printing (NBDP).

The dedicated transmitting frequency of the NAVTEX system is 518 kHz. The system uses only one single frequency. To avoid mutual interference, both limited transmitter power and frequency time-sharing are required.

Careful coordination of broadcast schedules is imperative, and gives room for up to 24 stations in one NAVAREA. These 24 stations are divided into 4 groups consisting of 6 transmitting stations. Every group is al­lowed one hour of transmission time, and this means that every station can be “on the air” for 10 minutes every four hours. Areas with few stations will allow longer transmitting times.

Navareas

The figure on the next page shows the different NAVAREAs worldwide. There are 16 of them altogether. The NAVTEX stations are geographically separated (A-Z), and the stations have their own “hours of duty”. Within the different Navareas, every Navtex station has its own identification character. This character is always a part of the preamble to the message.

Navarea I

The NAVTEX system started as early as 1980. The Barents Sea, the Nor­wegian Sea, the North Sea, the Baltic Sea, the English Channel and the Bay of Biscay are covered by NAVAREA I stations.

The table on page 122 shows all NAVTEX stations in NAVAREA I. Every station has its own characters for identification purposes. Which Navtex stations cover which particular areas is shown in the “List of Radio determination and Special Service Stations”.

Navareas System Coverage
Navareas worldwide
Table of Navtex stations
Navtex stations in Navarea I
Note that every NAVTEX station has a special identification character (ID). This category is always a part of the preamble to the message.
The Navtex structure
The Navtex coordinator

The NAVTEX coordinator in each NAVAREA decides which MSI messages the system is to broadcast.

Building up a Navtex Message

We will now consider the preamble of a NAVTEX message. The dedicated Navtex receiver has the ability to select which messages are to be printed out according to:

  1. A four-character technical code (B1, B2, B3, B4) which appears in the preamble of each message.
  2. Whether or not the particular message has already been printed.

Certain essential classes of safety information, such as navigational warnings, meteorological warnings and SAR information are non-rejectable to ensure that ships using NAVTEX always receive the most important information.

Read also: Inmarsat: A Guide to Satellite Communication

The technical code B1 is a single character identification assigned uniquely to each station in a region (Navarea), allowing the navigator to select only broadcasting station(s) serving the region of interest.

The B2 character identifies the different classes of messages, as identified below, in order that the user may reject those which he does not require.

The subject indicators in use are:

  • A – Navigational warnings (1).
  • B – Meteorological warnings (1).
  • C – Ice reports.
  • D – Search and Rescue Information/Piracy information (1).
  • E – Meteorological forecasts.
  • F – Pilot service messages.
  • G – DECCA messages.
  • H – LORAN messages.
  • I – OMEGA messages.
  • J – SATNAV messages.
  • K – Other electronic navaid messages (2).
  • L – Navigational warnings for mobile drilling rig movements (1).
  • V – Amplifying navigational warning information initially announced under “A”.
  • Z – No messages on hand.
  1. Cannot be rejected by the receiver.
  2. Messages concerning radionavigation services.

The B3 and B4 characters of the technical code, number the messages from 01 to 99 in order of receipt by the sender, with the numbering maintained separately for each broadcast station B1 and subject class B2. The numbering starts over again using the numbers of expired messages after number 99 has been assigned.

Categories B3 and B4’s use of “00” (zero) acts to ensure that, regardless of broadcasting station (B1) or whatever has already been received by the station in correct form, the message will be printed out by all receiv­ers within range of the transmitting station.

Type D messages (SAR-information) will always be numbered “00” (zero)

Example: NAVTEX preamble
NAVTEX message identifier
NAVTEX preamble

Examples of Navtex Messages

ZCZC GA20
WZ 1262
ORKNEY ISLANDS
LOTHER ROCK RACON 58-44N 02-49W
TEMPORARILY OFF AIR
NNNN

In the example above, Cullercoats Radio has transmitted a navigational warning with serial number 20.

ZCZC GL67
WZ 1253
RIGMOVE. SOUTHERN NORTH SEATCHARLES
ROWAN” AT 54-19N 02-07.7E
CANCEL THIS MESSAGE 121030 Z OCT 91
NNNN

The example above shows an additional navigational warning sent by Cullercoats Radio numbered 67.

ZCZC PB68
NETHERLANDS COASTGUARD
GALE WARNING NR.55 280630Z OCT
DOVER THAMES – SOUTH 8
OTHER DISTRICTS – NO WARNINGS
NNNN

This example shows a gale warning from Scheveningen Radio numbered as 55.

National Navtex service

Earlier in this article we looked at the International NAVTEX service. The system uses the English language and is built up in the same way all over the world.

National transmissions, however, use the national language, but the preamble of the message has the same format as required by international agreement. Frequencies allocated are 490 kHz and 4 209,5 kHz.

The Navtex receiver

Newer NAVTEX receivers are very compact, and are equipped with a built-in hard copy printer. Asa result of modern technology, the ship is able to receive automated broadcast messages (MSI) on a 24 hour basis. The messages received are stored and printed out by the built-in printer. The micro processor prevents more than one printout per message. The Navtex receiver is of relatively small size, and therefore constitutes very useful additional equipment for smaller fishing vessels and yachts.

Technical specifications:

  • International RX-freq.: 518 kHz;
  • National RX-freq.: 490 kHz;
  • Reception mode: FIB, Forward Error Correction;
  • Range: 200 – 400 nautical miles.
Furuno NX-700A
Navtex receiver

EGC – Enhanced Group Call

The EGC (Enhanced Group Call) services were developed by Inmarsat: A Guide to Satellite CommunicationInmarsat to achieve access to a unique global automatic service, capable of addressing traffic to predetermined groups of ships, or ships in both fixed and variable geographical areas.

The system gives ships access to different warnings, forecasts, shore-to-ship distress alerts, news and other necessary information. In addition to covering mid-ocean areas, the EGC system can offer automatic services in coastal waters where it may not be possible to establish the NAVTEX service.

A special feature of this system is the possibility of directing a call to a given geographical area. The area can be defined as a NAVAREA/METAREA, or may be uniquely defined. This feature of the EGC system is useful for such things as local storm warnings, or shore-to-ship alerts, regarding which it is inappropriate to alert all ships in an Ocean Region. Two EGC services are available:

The SafetyNET Service

The SafetyNET service allows an Information Provider, such as a meteorological or hydrographic office, to broadcast Maritime SafetyNET Service by InmarsatMaritime Safety Information (MSI) addressed to all, or selected, SES’s within an ocean region.

The FleetNET Service

The FleetNET service is a commercial service and allows an Information Provider such as shipping companies or governments to broadcast information such as company news, or government information to selected SESs belonging to a closed network. To receive a FleetNET message, a SES must have downloaded the appropriate ENID code, and be synchronized to the appropriate NCS Common Channel. (ENIDEGC Network Identification).

EGC system
Basic concepts of the EGC system

SafetyNET broadcast messages

The following types of messages are broadcast via the EGC SafetyNET:

  • Coastal warnings (Note 1);
  • Navigational warnings;
  • Meteorological warnings;
  • Ice reports;
  • Search and rescue information;
  • Meteorological forecasts;
  • Pilot service messages;
  • Decca system messages;
  • Loran system messages;
  • Omega system messages;
  • Satnav (GPS etc.) system messages;
  • Other electronic navaid messages;
  • Additional navigational warnings;
  • Meteorological and NAVAREA warnings and meteorological forecasts to ships within specified NAVAREAs/METAREAs;
  • Search-and-rescue co-ordination to fixed areas;
  • Search-and-rescue co-ordination to ships within specified circular areas;
  • Shore-to-ship distress alerts to ships within specified circular areas;
  • Urgency messages and navigational warnings to ships within specified rectangular areas;
  • Chart correction services (under development).

Notes:

1 The SafetyNET coastal warning broadcast facility is made available for transmissions of coastal information to areas where NAVTEX MSI is not provided

2 MSI messages are generally broadcast with a key-word in their header indicating the priority of the message – for example:

  • DISTRESS or MAYDAY for priority 3,
  • URGENT or PAN PAN for priority 2,
  • SAFETY or SECURITE for priority 1.

3 In some areas SafetyNET MSI broadcast is limited, while information providers are being established, see following table. Corrected “List of Radio Signals” will show current situation.

Availability of MSI in different NAVAREAS/METAREAS

In order to avoid the duplication of broadcasts, IMO has authorized the following arrangements:

For a given NAVAREA/METAREA which is covered by more than one Empowering Global Communication with INMARSAT Satellites in shippingOcean Region satellite, scheduled broadcasts of MSI, such as meteorological warnings and meteorological information, are made only via a single satellite/Ocean Region.

The SafetyNet structure
The SafetyNet System

For a given NAVAREA/METAREA which is covered by more than one Ocean Region satellite, unscheduled broadcasts of MSI, such as gale warnings and distress relay alerts, are made via all satellites/Ocean regions that cover the area in question.

MSI Broadcast Status Table
Status of MSI broadcast in the international safetynet service

NOTES ON THE TABLE:

  1. X = Full service available
  2. IMO has decided that routine broadcasts of Navigational Warnings and Meteorological Forecasts will be made at scheduled times over a single nominated satellite for each NAVAREA/METAREA. Unscheduled broadcasts of SAR Alert Relays and severe weather warnings will be made over all satellites which serve the area in question. See the Inmarsat Maritime Communication Handbook (Issue 2) for further guidance.
  3. India provides meteorological forecasts and warnings in METAREA VIII north of equator through CES Arvi(IOR). Mauritius/La Reunion provides meteorological forecasts and warnings for METAREA VIII south of equator through CES Burum, Station 12(IOR).
  4. Full operational service expected in June 1998.
  5. South of 60 degrees north, full service is provided by Japan.
EGC message broadcast
EGC message broadcast on NCS common channel

EGC broadcast to ships in NAVAREA I.

The figure also shows Navareas throughout the world.

The Navarea system in action
Navareas throughout the world

Reception of EGC messages – operating your EGC receiver

The EGC receiver is designed to continuously monitor the broadcast channel (the Inmarsat-C NCS common channel) and to process EGC SafetyNET messages transmitted over the satellite.

Note that certain classes of receiving equipment are not able to provide uninterrupted monitoring of the NCS Common Channel.

Inmarsat-C SESs classes
Different classes of Inmarsat-C SESs

CLASS – 0 – OPTION 1: (standalone EGC receiver)

This type of SES can only receive EGC messages (there are no class 1 maritime terminals).

CLASS 2:

The SES can receive EGC messages when not engaged in normal (non EGC) message reception. When the SES receiver is engaged in normal message reception, it is tuned to the message channel assigned by the CES. As long as normal message reception is going on, the SES receiver is not tuned to the NCS Common Channel. Incoming EGC messages during this time will not be received.

Generally many EGCSafetyNET messages will be repeated so it is possible to receive messages later if your EGC receiver is listening to the NCS Common Channel.

It will be interesting: Transmission of Urgency and Safety Signals from a Vessel

Normally unscheduled broadcasts such as distress alerts/gale warnings are re-broadcast 6 minutes after the initial transmission. Scheduled broad casts, like Informed for Safe Navigation at Sea with Critical Maritime Informationnavigational warnings and other messages valid for a period of time are repeated during the scheduled time as long as they remain in force.

CLASS 3:

The SES has two independent receivers, one capable of Inmarsat-C System Operation: From IMN to SCADAInmarsat-C message transfer at any time, and the other for EGC reception at any time. So operation of both modes without interruption is possible using this terminal configuration on board.

To obtain optimum results from the SafetyNET service, the operator must carefully read the manufacturers instructions for specific information about the following items:

Selective reception of messages

The receiver is supplied with software which stores the geographical boundaries of the NAVAREAS. The receiver uses this information to printout only messages applicable to the current area, plus any other areas which are programmed by the operator. The receiver can be programmed to print only essential messages and reject all other messages.

Updating the receiver regularly with ship’s position

Make sure that your EGC receiver is updated regularly with the ship’s position, in order to:

  • Make sure that the receiver will print out all messages addressed to a geographical area.
  • Print out messages for the required areas.

Note: If the EGC receiver has not been updated with the ships position for 12/24 hours (depending on model) the receiver will print/store all geographically addressed messages within the entire Ocean Region, the position can be updated in two ways:

  1. Automatically – using an electronic navigational device, e. g. a GPS (Global Positioning System).
  2. Manually – by typing the position directly into the terminal, IMO requires this to be done every 4 hours.

Mandatory EGCSafetyNET messages

The following types of EGCSafetyNET MSI messages are mandatory (SOLAS requirements):

  • Shore-to-ship distress alerts for the current NAVAREAS;
  • Navigational warnings for the current NAVAREA;
  • Meteorological warnings for the current NAVAREA.

Note: Currently produced EGC receiver models are supplied with software which automatically selects the mandatory message types shown above. With some earlier models, however, the software does not select these mandatory message types automatically, consequently the operator must programme the EGC receiver manually.

Optional EGCSafetyNET messages

In addition to the mandatory messages, IMO recommends that the EGC receiver also be programmed to receive the following messages:

  • Meteorological forecasts.
  • MSI for any other NAVAREAS in which the ship is expected to sail.

Reducing the number of alarms

The EGC receiver is programmed to give an audible/visual alarm on printing any GMDSS Distress and Safety Communicationsdistress alerts or urgent messages which require immediate response.

To avoid unnecessary alarms be sure to do the following:

  • keep the ships position updated, to ensure that the receiver receives messages relevant to the ship’s position.
  • set the receiver only to give alarms for messages with priority distress and urgency.

Maintaining good operating practice

  • Make sure that all equipment associated with the EGC receiver is working properly. Check that the printer is loaded with paper/ribbon. Make sure that the terminal is not storing messages that are unwanted and that it has enough storage space for new messages.
  • Make sure that the terminal is regularly updated with the ship’s cur­rent position
  • Feed the terminal with NAVAREA/METAREA and coastal warnings relevant for the ship’s voyage.
  • When staying in port, run the EGC receiver to make sure that it is functioning and to receive all relevant MSI messages before sailing.
  • Scheduled MSI broadcasts are found in the current “List of Radio Signals”. Make sure that the EGC receiver is tuned to the appropriate NCS Channel you want to listen to at the scheduled time given in the “List of Radio Signals” (scan the desired Ocean Region).
  • Keep a written log of the identities of all received messages, and printed copy of all distress traffic. Other messages should be kept on the bridge as long as they remain in force.

Missed messages

If, for example, you have missed a scheduled broadcast, try the following:

  • Switch the terminal off and on again. This action will clear the inter­nal memory of all stored messages, IDs. If the message is re-broad­cast, your EGC receiver will not reject it as a repeated message, and will print/store it.
  • Check if the CES that broadcast the message offers a re-broadcast facility, (This service is chargeable from some CESs).

EGC – message examples

NO.1

EGC. 477 Page 1 UTC Time: 95-07-12 02:08:15

LES 1 – MSG – 28915 – Met/NavWam/Fore Safety Call to AREA: 4 – PosOK NAVAREAIV 582/95(27). OLD BAHAMA CHANNEL
185 FOOT FREIGHTER BEBO, GRAY HULL, WHITE
SUPERSRUCTURE WITH BRIDGE AFT, DISABLED AND
ADRIFT VICINITY 21-47N 82-21W. VESSEL REPORTS
FUEL PUMPS PROBLEMS AND IS REQUESTING TOW TO
THE BAHAMA BANK ANCHOR. VESSELS IN VICINITY
REQUESTED TO MAINTAIN SHARP LOOK OUT, ASSIST
IF POSSIBLE AND REPORT SIGHTINGS TO U. S COAST
GUARD.

NO.2

EGC 255 Page 1 UTC Time: 97.07.01 00:11:03

LES 322 MSG 25468 Nav/MetWam/Fore Safety Call to Area 10 – NoPos Y0701133/2
SECURITE
FM MRCC AUSTRALIA 010002Z JUL 97
NAVAREA X 011/97
HASTING ISLAND LIGHT K3446 POSITION 10 20.5S
151 52.0E REPORTED UNLIT
NNNN

NO.3

EGC 926 PAGE 1 UTC Time; 94-08-24 09:06:31

LES 121 MSG 2498 – MetWam/Fore Urgent Call to Area: 2 – PosOK
WARNING ON NAVAREA 2, ISSUED BY METEO-FRANCE,
TOULOUSE
WIND SPEED IN BEAUFORT SCALE
WARNING N004
WEST OF FARADAY
FROM 24 AUGUST AT 09 UTC TO 24 AUGUST AT 18 UTC
SOUTHWEST 8. =
EGC 926
NNNN

NO.4

(Heading of an EGC message)

LES 102 – MSG 1104 – SAR Distress Call to
Area: 47 N 28 W 200 PosOK

message………

EXPLANATION OF THE EGC MESSAGES SHOWN ABOVE

The above messages show a typical MSI broadcast as it is received on your terminal.

Note the following:

  • The date and time of the messages in UTC time.
  • Identification of the CES sending the message. UTC Inmarsat-C CES in EGC message 3.
  • The unique number identifying the message, which is 2498 in EGC message 3.
  • The priority of the message, in message 1, SAFETY, message 2, SAFETY and in message 3, URGENCY. When receiving DISTRESS/URGENT messages the terminal will respond automatically giving an audible/visual alarm.
  • The nature of the message, message 3 is a Meteorological Warning for METAREA II.
  • The term NoPos, this is a message giving information to the operator that the EGC receiver has NOT been updated with the ship’s position during the past 12/24 hours. The term PosOK indicates that the EGC receiver has been updated with ship’s position.
  • In figure 4 there is a message heading which calls up ships within a circular area centred on 47 degrees North and 28 degrees West with a radius of 200 nautical miles. It is also possible to address messages to a rectangular area giving the co-ordinates of the southwest comer, and the easterly and northerly degrees. Note that in example number 4, the priority is DISTRESS.

High frequency (HF) MSI

The GMDSS also allows the reception of MSI via HF telex. Warnings for the different NAVAREAS are transmitted at fixed times and frequencies.

The “List of Radiodetermination and Special Service Stations” provides transmission times, DSC (Digital Selective Calling) Procedures for VHF – MF and HFfrequencies and coast stations for the different NAVAREAS. Students should also study the “List of Coast Stations”, Annex II, Part C, which gives particulars of coast stations transmitting MSI messages to ships by means of NBDP techniques.

NAVTEX station list
Nav-AreaCoast StationStn IDCountry1st TX of Day (UTC)Interval (hrs)
IOostendeMBelgium02004h
OostendeTBelgium02484h
TallinUEstonia00304h
ReykjavikRIceland03404h
ValentiaVIreland03484h
Netherlands C. G.PNetherlands03404h
SvalbardANorway00184h
BodoBNorway00184h
RogalandLNorway00184h
VardoVNorway03404h
MurmanskCRussia02004h
ArkhangelskFRussia02004h
BjuröklubbHSweden00044h
GislövshammarJSweden00304h
StåvsnäsUSweden00304h
CullercoastGU. K.01084h
NitonKU. K.01404h
PortpatrickOU. K.03084h
NitonSU. K.00184h
IICross CorsenAFrance00004h
Horta RadioFPortugal00504h
Monsanto RadioDPortugal02504h
CorunaGSpain00304h
TarifaISpain01204h
Las PalmasISpain01204h
IIIVarnaJBulgaria01304h
SplitQCroatia01304h
TroodosMCyprus00204h
SerapeumXEgypt03504h
Cross La CardeHFrance03404h
IVBermudaBBermuda00104h
Sept IlesCCanada00204h
WiartonDCanada01104h
St. JohnsOCanada02204h
Thunder BayQCanada02304h
SydneyYCanada03004h
YarmouthJCanada03254h
LabradorVCanada03354h
MiamiAUSA00454h
BostonFUSA00454h
New OrleansUUSA03004h
PortsmouthNUSA01304h
San JuanRPuerto Rico02004h
VColoniaUruguayPlanned
Laguna del SauceUruguayPlanned
La PalomaUruguayPlanned
MontevideoUruguayPlanned
Punta del EsteUruguayPlanned
SaltoUruguayPlanned
VIUshuaiaAArgentina0240Under trial
Rio GallegosBArgentina0410Under trial
Com. RivadaviaCArgentina0400Under trial
Bahia BlancaDArgentina0210Under trial
Mar del PlataEArgentina0110Under trial
Buenos AiresFArgentina05106h
RosarioGArgentina0010Under trial
VIIWalvis BayBNamibiaPlanned
Cape TownCSouth Africa00204h
Port ElizabethQSouth Africa02204h
DurbanDSouth Africa01204h
VIIIBombayGIndia01004h
MadrasHIndia02304h
Mauritius RadioPMauritiusPlanned
IXBahrain RadioBBahrainPlanned
SerapeumXEgypt0350
DammamGSaudi Arabia06056h
JeddahHSaudi Arabia07056-12h
MuscatNSaudi Arabia0200
XNONE*
XISanyaMChina0200Planned
GuangzhouNChina02104h
FuzhouOChina0220Planned
ShanghaiQChina02404h
DalianRChina02504h
JayapuraAIndonesia00004h
AmbonBIndonesia00204h
MakassarDIndonesia00304h
JakartaEIndonesia00404h
OtaruJJapan01304h
KushiroKJapan01404h
YokohamaIJapan01204h
MojiHJapan01104h
NahaGJapan01004h
SingaporeCSingapore00504h
Bangkok RadioFThailand00504h
GuamVUSA01004h
XIVNONE
XVIPaitaSPeru03004h
CallaoBPeru03204h
MollendoWPeru03404h
*Australia only provides coastal warnings through the International SafetyNet Service
Author
Author photo - Olga Nesvetailova
Freelancer
Literature
  1. Global Maritime Distress and Safety System: IMO 1987.
  2. Manual for use by The Maritime Mobile and Maritime Mobile- Satellite Services: ITU 1992.
  3. Radio Regulations 1-2-3: ITU 1990.
  4. Manual for Norwegian Mobile Radiotelephone Stations: The Norwegian Telecom 1992.
  5. Modem Electronic Communication: Gary M. Miller 1978.
  6. Brochures and data sheets from manufacturers of GMDSS Equipment.
  7. Inmarsat: Inmarsat-A User’s Manual, Inmarsat-C User’s Manual.
  8. Nodposisjonering: Bjomar Augdal, 1992.
  9. Skipsantenner: Bjomar Augdal 1991.
  10. COSPAS-SARSAT Secretariat: COSPAS-SARSAT System Data Documents.
  11. Admiralty List of Radio Signals.
Footnotes
Sea-Man

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