GMDSS & Safety

Paul Gunton
Paul Gunton

20 January 2019

GMDSS & Safety

Regardless of whether or not a ship makes use of modern communications infrastructure and equipment for commercial and welfare reasons, it is obliged to do so for safety purposes under GMDSS (Global Maritime Distress and Safety System) which 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.

Today, the GMDSS infrastructure and system is undergoing its first restructuring and although the changes may not all be in place in the immediate future, the changes will see an initial opening up of the allowed means of communication to new service providers.

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.

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. 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 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. The 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.

In 2018, after more than four years of lobbying, Iridium was finally given the green light as an authorised GMDSS supplier at MSC 99 so ending Inmarsat’s monopoly on safety service provision. Before Iridium can commence providing services it must first enter into a Public Services Agreement with IMSO and begin production of suitable equipment either directly or in conjunction with equipment suppliers. Iridium is expected to be in a position to begin services in 2020.

At the same MSC meeting in May, Inmarsat’s Fleet Broadband service was also given approval for use in GMDSS.

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).

Beyond GMDSS

Safety communications are not confined to the GMDSS requirements alone as there are other areas of SOLAS where communications that relate to safety are mandated and beyond that there are voluntary equipment that can be used to enhance safety some of which will interact with GMDSS.

Included among the various equipment and systems outside of GMDSS are personal locator beacons (PLBs) which transmit alerts on emergency frequencies and also mandatory radar equipment which makes use of the communications spectrum. Technically ships’ radar systems operate using radio transmissions but they are not considered as communication devices, but another collision avoidance system is because it transmits information intended to be used by other vessels and shore stations.

The Automatic Identification System (AIS) was initially developed purely as a response to the issue of collision avoidance and as a corollary to aid shore-based VTS operators as well as navigators on ships to properly identify radar targets. AIS consists of a transponder system in which ships continually transmit their ID, position, course, speed and other data over VHF. The data transmitted is derived from ships equipment as regards position, course and speed, from initial input for the ID which comprises ship’s name and call sign and from direct manual input for other details such as port of destination and type of cargo.

Updated information is transmitted at regular intervals of very short duration. When received on the other ships, the data is decoded and displayed for the officer of the watch, who can view AIS reports from all other AIS-equipped ships within range in graphic and text format. The AIS data may optionally be fed to the ship’s integrated navigation systems and radar plotting systems to provide AIS “tags” for radar targets. It can also be logged to the ship’s Voyage Data Recorder (VDR) for playback and future analysis.

In 2000, IMO adopted a new requirement as part of a revised new chapter V for all ships to carry AIS capable of providing information about the ship to other ships and to coastal authorities automatically. The regulation requires AIS to be fitted aboard all ships of 300gt and upwards engaged on international voyages, cargo ships of 500gt and upwards not engaged on international voyages and all passenger ships irrespective of size. The requirement became effective for all ships by 31 December 2004.

The IMO regulation requires ships fitted with AIS to maintain AIS in operation at all times except where international agreements, rules or standards provide for the protection of navigational information. The regulation requires that the AIS must provide information - including the ship’s identity, type, position, course, speed, navigational status and other safety related information - automatically to appropriately equipped shore stations, other ships and aircraft and to receive automatically such information from similarly fitted ships.

AIS transmitters can also be attached to navigational marks or to hazards and transmit information that will complement the sight/sound signals that may be present. These fixed AIS transmitters can also be used to give other information such as current strength and direction.

Although initially intended only for navigation use by ships and shore authorities, AIS data is now regularly disseminated by commercial operations either to subscribers or on a gratis basis allowing almost anyone to determine any specific ship’s current whereabouts and operational status. The IMO does not condone this use but appears powerless to prevent it.

Because AIS operates on VHF radio, there is a natural limit to the distance over which it can be transmitted. However, there is a small but growing number of service providers using satellites that can receive AIS signals when ships are out of the range of shore stations. These services are generally referred to as satellite AIS or S-AIS. Most of the service providers say that their services are targeted purely at national security organisations but others make no secret of the fact that their customers are often commercial organisations including commodity traders and analysts.

It is fair to say that AIS has not been universally welcomed by navigators or ship operators. Many believe that its introduction was rushed and insufficient thought given to its use under operational circumstances. Officially AIS is an aid to navigation and not a collision avoidance method in its own right. Some seafarers believe that AIS overrides COLREGS but official advice from some flag states makes clear this is not so.

Just as with radar in its early days, AIS has been blamed for causing rather than helping to avoid collisions. One of the factors that many say was ill considered was the fact that by being obliged to transmit its identity, cargo and destination, a ship can easily be identified by those with criminal intent or even terrorists. Some operators address this by either transmitting false information at certain stages of a voyage or by switching the device off except when in very close traffic situations.


As the IMO further develops the concept of e-navigation a potential new technology that is referred to as AIS on steroids is being explored. VHF had traditionally been used for voice transmission until the advent of AIS. VHF Data Exchange System (VDES) began as a concept developed by the International Association of Lighthouse Authorities (IALA) e-NAV Committee. It was originally developed to address emerging indications of overload of VHF Data Link (VDL) of AIS and simultaneously enabling a wider seamless data exchange for the maritime community.

With VDES it will be possible to send broadband data making it more economical for ships to maintain a data connection at sea by eliminating the need to use satellites in coastal waters, while not compromising on the global connectivity satellites will be able to provide in the future. VDES is expected to cover up to 50 kilometres from the nearest land-based equipment, which will allow ships to benefit from modern communication and navigation methods without increasing costs.

VDES is capable of facilitating numerous applications for safety and security of navigation, protection of marine environment, efficiency of shipping and others. Proponents claim it could have a significant beneficial impact on maritime information services including Aids to Navigation and VTS in the future.

An EU-funded project under the title EfficienSea2 is testing the potential of VDES and in May 2017 it was announced Cobham SATCOM which is participating in the project had tested VDES in sending and receiving data at sea. The trials took place aboard Scandlines’ hybrid ferries operating in the Baltic Sea.

Ship security alert system (SSAS)

Following the terrorist attacks in New York in September 2001, the IMO Diplomatic Conference on Maritime Security held in London in December 2002 adopted several amendments to SOLAS. These amendments include the introduction of Maritime Security in Chapter XI of SOLAS 74 and incorporated the International Ship and Port Facility Security (ISPS) Code which came into effect on 1 July 2004.

As a consequence, all passenger vessels and other ships over 500gt are required to be provided with a ship security alert system (SSAS). The requirements of the system are specified in Regulation 6 of Chapter XI-2 of SOLAS 74. In regard to Regulation 6.2.1, the ship security alert system, when activated by the ship shall:

  • initiate and transmit a ship-to-shore security alert to a competent authority designated by the Administration, which in these circumstances may include the Company, identifying the ship, its location and indicating that the security of the ship is under threat or it has been compromised;
  • not send the ship security alert to any other ships;
  • not raise any alarm on board the ship; and
  • continue the ship security alert until deactivated and/or reset.

The regulation goes on to say that the SSAS shall be capable of being activated from the navigation bridge and in at least one other location and conform to performance standards not inferior to those adopted by the Organization. The SSAS activation points must be designed so as to prevent the inadvertent initiation of the ship security alert.

When a flag state receives notification of a ship security alert it is obliged to immediately notify the state(s) in the vicinity of which the ship is presently operating. If the alert is received by any state other than the flag state, that Contracting Government should immediately notify the relevant flag state and, if appropriate, the state(s) in the vicinity of which the ship is presently operating.

The exact type of equipment that can be used to satisfy the regulation is not specified but some operators have chosen to make use of the GMDSS radio station while many others have installed separate and dedicated satellite equipment. By the standards of modern communications technology, SSAS is quite basic comprising a GPS receiver linked to a transmitter, a power supply, some software and activation buttons.

Because the technology is simple and the market huge, a sizeable number of manufacturers have come up with SSAS products. They can all be expected to meet the necessary legal obligations but the ways in which they do this vary somewhat. The principal differences centre on the methods used to transmit the alarm message, but there are also a number of other features and benefits. As an example, some suppliers will act as co-ordinating centre and when an alert signal is received they will contact selected personnel of the owner or manager. At least one – Pole Star – has developed an app for smart phones that will give all the information to designated persons whenever an alert is made.

Long range identification & tracking (LRIT)

After the use of AIS for reasons of security (rather than its intended aim of an aid to navigation) was found to be inefficient, at MSC 81in 2006 the IMO adopted proposals for long-range tracking and identification of ships (LRIT), to form part of SOLAS Chapter V.

The obligations of ships to transmit LRIT information and the rights and obligations of SOLAS Contracting Governments and of Search and rescue services to receive LRIT information are established in regulation V/19-1 of SOLAS. Provisions of the amendment came into force in 2009 after which all internationally-trading vessels over 300gt operating outside of GMDSS Sea Areas A1 were required to install the necessary equipment and transmit via satellite technology their identity, location, date and time of position to shoreside bodies authorised to receive it. Ships operating exclusively in coastal Sea Area A1 and fitted with an AIS are exempt.

LRIT requires ships to make regular transmissions of identification and position every six hours to a tracking service which can only release the information with the authority of the vessel’s flag state. Other states with an interest in particular ships may make applications to the flag state for access to the information.

If security levels are raised, or if a particular ship becomes of special interest, then the regularity of transmissions and monitoring may be stepped up to as much as once every 15 minutes. The operating standards for LRIT demand that the transmissions can be controlled remotely, without intervention on board. Effectively this means that the transmitter must be of a type that can be polled by a service nominated by the flag state.

Unusually for a new IMO regulation, the vast majority of ships were not required to install any new equipment but only certification proving that whatever was on board and intended for use was in compliance with the LRIT equipment requirements. For most vessels the Inmarsat C GMDSS system is acceptable, as are some SSAS devices. Some Iridium systems are also approved for LRIT compliance. Whatever equipment is used must either have its own in-built GPS system or be connected to an external GPS.

Ensuring that ships comply with the LRIT regulations is the responsibility of the flag state. Under the LRIT framework, each state can either establish a national data centre (DC) or join with others to form a regional or co-operative data centre. Flag states have appointed Application Service Providers (ASP) to manage communications between the ship, the Communication Service Provider (CSP) and the DC. All information is stored by the various DCs and passed to other centres and states when authorized by a ship’s flag state. The choice of ASP is down to the ship operator from any appointed by the flag state. Many ASPs have been appointed by several flag states.

The LRIT system has now been in operation for several years and while it appears to be functioning as intended there is not universal satisfaction with it. The costs of the six-hourly transmissions are borne by the flag state and some are finding this a heavy financial burden especially as most of the data is simply received and stored and never requested by any other contracting government. As an example, during the period from 1 January to 30 June 2014, Liberian flagged vessels transmitted 2,204,031 position reports of which only 17% were requested by Contracting Governments.

It has been proposed that AIS and S-AIS could provide an alternative because there is no immediate cost involved in any transmission. The question is under discussion but whether all flag states are happy for information collected by commercial enterprises from vessels on the high seas to be sold to other governments and organisations and individuals prepared to subscribe remains to be seen. Another option proposed at MSC 95 in 2015 was to reduce the number of daily transmissions from four to two. There was support for this proposition but no action has yet been put in place to implement a change. At NCSR4 in 2017, two options were proposed for further consideration so the matter is still to be finalised.