What is GMDSS?

What is GMDSS?

Malcolm Latarche

Malcolm Latarche · 10 June 2017


Some 30 years after the first ever communications satellite was put into orbit, the roll out of GMDSS (Global Maritime Distress and Safety System) began in 1992. Although it did not entirely replace radio, GMDSS was aimed at putting satellite technology at the heart of safety communications system for maritime users. The advent of GMDSS saw a major change in the way all communications including commercial messages were handled on ships. It also ensured the demise of the dedicated radio officer.

Although probably responsible for saving many lives, the maritime communication system that existed prior to GMDSS suffered from a multitude of limitations. GMDSS is an international system which uses land-based and satellite technology and ship-board radio-systems to ensure rapid, automated, alerting of shore based communication and rescue authorities, in addition to ships in the immediate vicinity, in the event of a marine distress. It was adopted by the IMO by way of amendments to SOLAS 1974 Chapter IV in 1988 and entered into force on 1 February 1992 with a phase-in period running until 1 February 1999 depending on ship type and size. With the phase-in period now well in the past, all ships are now subject to the full GMDSS carriage and maintenance requirements which vary depending on ship type and area of operation.

A comprehensive review of GMDSS began in 2012 and in March 2016 at the Navigation, Communications and Search and Rescue sub-committee’s third meeting (NCSR3) it was recommended that an agreed two-year modernisation plan should be got underway with a completion date in 2018 – a year later than the initial date when the review was initiated.

The review will require changes to Chapters VI and V of SOLAS but this will take time and it is now expected that it will be 2024 before the changes come into effect. Currently there are no planned changes to carriage requirements but that is no guarantee for the long term. The integration of communications and navigation equipment that is being considered as part of the e-navigation project is seen as being desirable but with numerous hurdles to overcome. The e-navigation concept itself is still somewhat nebulous and its development direction is still unclear.

NCSR3 also decided that proposals to interconnect NAVTEX and Inmarsat SafetyNet in Integrated Navigation Systems should be delayed while performance standards for INS are not yet adopted. At NCSR4 it was finally agreed to amend performance standards as necessary to enable the interconnection and the proposal was sent to MSC98 in June 2017.

However, the MSC meeting decided that in order to avoid multiple amendments to resolution MSC.252(83) on Revised performance standards for INS any necessary changes should be postponed until related work on the ‘Guidelines for the harmonised display of information received via communications equipment’ is completed at NCSR 5 in 2018.

The GMDSS review has been wide ranging and has looked at existing and emerging technologies that could be incorporated into the system. As an example the review has looked at the possible role of Automatic Identification System (AIS) in all its forms and emerging VHF Data Exchange System (VDES) technology. Bringing in these two services effectively links a future GMDSS with e-navigation but precisely how and to what extent remains to be seen.

A draft Modernization Plan of the GMDSS was completed at NCSR4 in march 2017 and submitted to the MSC for eventual approval. The aim is to eventually adopt a revised and updated SOLAS chapter IV, enabling the use of modern communication systems in GMDSS, while removing the requirement to carry obsolete systems, at the same time maintaining the requirements for ships to carry specified terrestrial and satellite radiocommunications equipment for sending and receiving distress alerts and maritime safety information, as well as for other communications.

Nothing in the plan at the moment will add to the carriage requirements but it will provide for the introduction of new services and systems, such as other terrestrial communications using digital technologies for broadcasting maritime safety and security related information from shore-to-ship, and for enhanced and more reliable Search and Rescue capabilities by, for example, including the Cospas-Sarsat MEOSAR system.

The plan also proposes the review of related regulations in other SOLAS chapters, including SOLAS chapter III (life-saving appliances), particularly in relation to search and rescue transponders, and the incorporation of maritime security communications in SOLAS chapter IV. Because of the reach of GMDSS through SOLAS, other areas will also be affected. For example, as the means of permitted communication expands, so will the complexity and the training needed for operators to ensure mistakes are not made.

As part of the plan MSC 98 held in June 2017 has adopted a number of resolutions. The IMO has not yet released the full details but as at the end of June 2017 these were known to be:

• Resolution MSC.430(98) – amendments to the revised performance standards for narrow-band direct-printing telegraph equipment for the reception of navigational and meteorological warnings and urgent information to ships (Navtex) (resolution MSC.148(77))
• Resolution MSC.431(98) – amendments to the revised performance standards for enhanced group call (egc) equipment (resolution MSC.306(87))
• Resolution MSC.432(98) – amendments to performance standards for multi-system shipborne radionavigation receivers (resolution MSC.401(95)) and
• Resolution MSC.434(98) – performance standards for a ship earth station for use in the GMDSS.

The scope of GMDSS and how it operates in practice even in its present form is vast and warrants a complete book in itself in the shape of the IMO-published GMDSS Manual. In this ShipInsight guide, only the basics and the equipment carriage and maintenance aspects are covered.

Under GMDSS, all ocean-going passenger ships and cargo ships of 300gt and above engaged on international voyages must be equipped with radio equipment that conforms to international standards as set out in the system. A survey of GMDSS equipment is needed at regular intervals for the ship to be issued with and retain a valid Safety Radio Certificate. Survey of radio installation on SOLAS ships should be carried out in accordance with the rules laid down in IMO Res. A.746(18) “Survey Guidelines under the harmonised system of survey and certification” R 8 (adopted by IMO), and SOLAS 1974 as amended, chapter I, part B.

The radio survey should always be performed by a fully qualified radio surveyor who has adequate knowledge of the IMO’s relevant conventions and associated performance standards and appropriate ITU Radio Regulations. It is considered as very important that the responsible radio operators are properly instructed and trained in how to use the GMDSS radio equipment. The radio licence and certificate for the radio operator/operators should be checked during the survey. There are a number of different types of GMDSS qualifications, currently these are as follows;

• First Class Radio-Electronic Certificate;
• Second Class Radio-Electronic Certificate; and
• GMDSS General Operator’s Certificate
• ROC (Restricted Operators Certificate)

The First and Second Radio-Electronic Certificates are intended for Ship’s Radio-Electronic Officers, who sail on GMDSS ships which use the option of at-sea electronic maintenance. The GMDSS General Operator’s Certificate is a non-technical operator qualification, designed for Navigating Officers. The GMDSS General Operator’s Certificate is normally awarded after a ten day course and examination.

Operational zones

For the purpose of GMDSS, four operational zones have been established loosely based on distance from shore and in range of different communication systems.

• SEA AREA A1: the area within the radiotelephone coverage of at least one VHF coast station in which continuous DSC (Digital Selective Calling) alerting is available;
• SEA AREA A2: the area, excluding Sea Area A1, within the radiotelephone coverage of at least one MF coast station in which continuous DSC (Digital Selective Calling) alerting is available;
• SEA AREA A3: the area, excluding Sea Areas A1 and A2, within the coverage of an Inmarsat geostationary satellite in which continuous alerting is available; and
• SEA AREA A4: an area outside sea areas A1, A2 and A3.

In practical terms, this means that ships operating exclusively within about 35 nautical miles from the shore may be able to carry only equipment for VHF-DSC communications; those which go beyond this distance, up to about 150 to 400 nautical miles from shore, should carry both VHF-DSC and MF-DSC equipment; while those operating further from the shore but within the footprints of the Inmarsat satellites should additionally carry approved Inmarsat terminal(s).

In the early days of GMDSS, Inmarsat C was the preferred option and minimum requirement where satellite services were mandated. Th larger Inmarsat A and B systems were also approved but these were quite expensive and considered as ‘overkill’ by many shipowners.

Current compliant services include Inmarsat B, Inmarsat C, Mini C and Fleet 77. Inmarsat’s satellite network is available in areas A1 to A3 but does not extend to area A4 which is effectively waters in Polar regions. In these areas HF communications are required although vessels equipped with Iridium communication systems can communicate with shore and ship to ship providing both vessels have the equipment.

Iridium has been lobbying to be accepted as a full GMDSS service provider for some years. Its application was reviewed by the NCSR1 meeting in July 2014 and recommended for further consideration by MSC 94. The November 2014 meeting of MSC decided that the International Maritime Satellite Organization (IMSO) should convene a group of experts to produce a technical and operational assessment of Iridium as a GMDSS mobile satellite service provider. At NCSR2 in March 2015, IMSO reported that it has started to prepare for the Iridium evaluation process. IMSO further said that it has established a Group of Experts to perform technical and operational evaluation and all five different elements (Space Segment, Mobile Terminals, Terrestrial Networks, GMDSS and Search and Rescue communications) will be dealt with in relation to Earth Stations. IMSO reported the technical and operational evaluation results to NCSR3 in March 2016 and concluded that Iridium did not yet meet all the requirements in Resolution A.1001(25) but could be considered as a GMDSS supplier once the technical requirements are met.

Radio rules in coastal waters

Only ships operating in areas A3 and A4 are obliged to carry satellite communications meaning radios (operating on VHF, HF and MF) are still considered the primary means of communication in emergency situations. In addition search and rescue transponders (SARTs) and NAVTEX (Navigational Telex) are also required for GMDSS compliance.
SARTs are devices which are used to locate survival craft or distressed vessels by creating a series of dots on a rescuing ship’s X-band radar display.

The detection range between these devices and ships, dependent upon the height of the ship’s radar mast and the height of the SART, is normally less than about ten miles. Initially only radar SARTS were allowed but since the advent of AIS, a hybrid AIS-SART has been permitted as an alternative. Most SARTs are mostly cylindrical and in safety orange colour.

NAVTEX is an international automated MF direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent marine safety information to ships. It was developed to provide a low-cost, simple, and automated means of receiving information aboard ships at sea within approximately 200 nautical miles off shore. A NAVTEX is usually a bracket mounted cabinet with a small LCD screen displaying
broadcast messages with an optional printout. Inmarsat’s SafetyNET service is an alternative to NAVTEX for ships that are equipped with satellite GMDSS equipment and it provides similar information.

Ensuring GMDSS availability

GMDSS regulations define three methods of ensuring availability of GMDSS equipment at sea:
• At sea electronic maintenance, requiring the carriage of a qualified radio/electronic officer (holding a GMDSS First or Second class Radio-Electronics Certificate) and adequate spares and manuals;
• Duplication of certain equipment; or
• Shore based maintenance

Ships engaged on voyages in sea areas A1 and A2 are required to use at least one of the three maintenance methods outlined above, or a combination as may be approved by their administration. Ships engaged on voyages in sea areas A3 and A4 are required to use at least two of the methods outlined above. The lower requirement for A1 and A2 areas recognises that being closer to shore, ships will have more opportunity to rectify problems.

The vast majority of ships do not opt for at sea maintenance preferring instead to duplicate the equipment and use shore based maintenance (for A3 ships), or use shore based maintenance only (A1 and A2 ships).

**GMDSS equipment is required to be powered from three sources of supply:**

• 'ship’s normal alternators/generators;'
• 'ship’s emergency alternator/generator (if fitted); and'
• 'a dedicated radio battery supply.'

The batteries are required to have a capacity to power the equipment for 1 hour on ships with an emergency generator, and 6 hours on ships not fitted with an emergency generator.

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