International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 5

Number 4

December 2011

453

1 INTRODUCTION

In 1988, the Conference of Contracting Govern-

ments to the 1974 SOLAS Convention on the Global

Maritime Distress and Safety System (GMDSS)

adopted amendments to the 1974 SOLAS Conven-

tion concerning radiocommunications for the

GMDSS. These amendments entered into force on

1 February 1992. On 1 February 1999 the GMDSS

has become implemented for all SOLAS ships.

Since full implementation of the GMDSS some

changes both of regulatory and technical nature have

occurred.

The Maritime Safety Committee (MSC) at its

81st session decided to include, in the work pro-

grammes of the NAV and Radiocommunications

and Search and Rescue (COMSAR) Sub-

Committees, a high priority item on "Development

of an e-navigation strategy". One of the fundamental

elements of e-navigation will be a data communica-

tion network based on the some GMDSS infrastruc-

ture elements. It follows that question on moderniza-

tion of the GMDSS is legitimate.

2 THE ORIGINAL CONCEPT OF THE GMDSS

The original concept of the GMDSS is that search

and rescue authorities ashore, as well as shipping in

the immediate vicinity of the ship in distress, will be

rapidly alerted to a distress incident so they can as-

sist in a coordinated search and rescue operation

with the minimum delay. The system also provides

for urgency and safety communications and the

promulgation of maritime safety information (MSI)

(Czajkowski, 2000).

2.1 Functional requirements

The GMDSS lays down nine principal communica-

tions functions which all ships, while at sea, need to

be able to perform (IMO, 2004):

1 transmitting ship-to-shore distress alerts by at

least two separate and independent means, each

using a different radiocommunication service;

2 receiving shore-to-ship distress alerts;

3 transmitting and receiving ship-to-ship distress

alerts;

4 transmitting and receiving search and rescue co-

ordinating communication;

5 transmitting and receiving on-scene communica-

tion;

6 transmitting and receiving signals for locating;

7 transmitting and receiving maritime safety infor-

mation;

8 transmitting and receiving general radiocommu-

nication from shorebased radio systems or net-

works;

9 transmitting and receiving bridge-to-bridge com-

munication.

Yesterday, Today and Tomorrow of the GMDSS

K. Korcz

Gdynia Maritime University, Gdynia, Poland

ABSTRACT: Basing on a general concept, the main functions and the international requirements the Global

Maritime Distress and Safety System (GMDSS) have been presented. The modifications of the system since

its implementation and its current status have been described. The future of the GMDSS has been discussed as

well.

454

2.2 Radiocommunication services

The following radio services are provided for the

GMDSS:

− a radiocommunication service utilizing geosta-

tionary satellites in the maritime mobile satellite

service (INMARSAT);

− a radiocommunication service utilizing polar or-

biting satellites in the mobile satellite service

(COSPAS-SARSAT);

− a radiocommunication service for transmitting

signals from survival craft stations in the 9200 –

9500 MHz band;

− the maritime mobile service in the bands between

156 MHz and 174 MHz (VHF);

− the maritime mobile service in the bands between

4,000 kHz and 27,500 kHz (HF);

− the maritime mobile service in the bands 415 kHz

to 535 kHz and 1,605 kHz to 4,000 kHz (MF).

2.3 GMDSS Sea areas

Radiocommunication services incorporated in the

GMDSS system have individual limitations with re-

spect to the geographical coverage and services pro-

vided. The range of communication equipment car-

ried on board the ship is determined not by the size

of the ship but by the area in which it operates. Four

sea areas for communications within the GMDSS

have been specified by the IMO. These areas are

designated as follows (IMO, 2004):

− Sea area A1 – an area within the radiotelephone

coverage of at least one VHF coast station in

which continuous DSC alerting is available.

− Sea area A2 – an area, excluding sea area A1,

within the radiotelephone coverage of at least one

MF coast station in which continuous DSC alert-

ing is available.

− Sea area A3 – an area, excluding sea areas A1

and A2, within the coverage of an INMARSAT

geostationary satellite in which continuous alert-

ing is available.

− Sea area A4 – an area outside sea areas A1, A2

and A3 (the polar regions north and south of 75°

latitude, outside the INMARSAT satellite cover-

age area).

2.4 Equipment carriage requirements

Based on the range limitations of each radiocommu-

nication service the four sea areas have been defined

according to the coverage of VHF, MF, HF Coast

Radio Services and Inmarsat services. The type of

radio equipment required to be carried by a ship is

therefore determined by the sea areas through which

a ship travels on its voyage.

2.5 GMDSS equipment and systems

The following equipment and systems are provided

for the GMDSS (Fig. 1):

− DSC - Digital Selective Calling;

− INMARSAT Satellite System;

− EPIRB - Emergency Position Indicating Radio-

Beacon (Inmarsat E, Cospas/Sarsat and VHF

DSC);

− SARTs - Search And Rescue Transponders;

− NAVTEX System;

− NBDP - Narrow Band Direct Printing;

− RTF - Radiotelephony;

− DMC - Distress Message Control;

− navigational equipment (for support).

Other elements of GMDSS to be showed in Fig.

1stand for as follows:

− CES - INMARSAT Coast Earth Station;

− SES - INMARSAT Ship Earth Station;

− LUT - COSPAS/SARSAT Local User Terminal;

− RCC - Rescue Coordination Centre.

CES

SES

EPIRB

DSC

VHF

NBDP

RTF

VHF

NAVIGAT.

EQUIPMENT

SARTs

NAVTEX

DMC

INMARSAT

COSPAS/

SARSAT

LUT

RCC

SAR

NBDP

DSC

RTF

NAVTEX

VHF

DSC

Figure 1. GMDSS equipment and systems (Korcz, 2007)

2.5.1 DSC specification

Digital selective calling (DSC) is designed for au-

tomatic station calling and distress alerting. Each

call consists of a packet of a digitized information.

DSC calls can be routed to all stations, to an indi-

vidual station or to a group of stations.

The system is used by ships and coast stations in

the MF, HF and VHF maritime communication

bands.

The system is a synchronous system using char-

acters composed from a ten bit error-detecting code.

The first seven bits are information bits. The last

three bits are used for error-detection. Each charac-

ter is sent twice but separated in time and a message

check character added at the end of the call.

455

Technical characteristics and operational proce-

dures for the use of DSC equipment are described in

the following documents:

− Recommendation ITU-R M.493 ‘Digital selective

calling system for use in the Maritime Mobile

Service’.

− Recommendation ITU-R M.541 ‘Operational

procedures for the use of digital selective-calling

(DSC) equipment in the Maritime Mobile Ser-

vice’.

2.5.2 Inmarsat specification

The original concept of the GMDSS includes

three Inmarsat services: A, B and C.

Inmarsat A provides two-way direct-dial phone

connection as well as fax, telex and data services at

rates between 9.6kbps up to 64kbps.

Inmarsat B was first maritime digital service,

launched in 1993, and remains a core service for the

maritime industry. It supports global voice, telex,

fax and data at speeds from 9.6kbps to 64kbps, as

well as GMDSS - compliant distress and safety

functions.

Inmarsat C is one of the most flexible mobile

satellite message communication systems, it has the

ability to handle commercial, operational and per-

sonal messages just as easily as distress and safety

communications.

It offers two-way, store-and-forward packet data

communication via a lightweight, low-cost terminal.

Inmarsat C is recommended for the any of the fol-

lowing applications:

− E-mail and messaging

− Fax and telex

− SMS text

− Remote monitoring

− Tracking

− Chart and weather updates

− Maritime safety information

− GMDSS

− SafetyNET and FleetNET

2.5.3 NBDP specification

The Narrow Band Direct Printing – NBDP (ra-

diotelex) systems employs error correction in the

form of ARQ (Automatic Retransmissions Request)

and FEC (Forward Error Correction). The technical

details of the error correction are defined by the

ITU-R in Recommendation M.476 and the Recom-

mendation M.625. Radiotelex is also known as Tel-

ex Over Radio (TOR).

2.5.4 NAVTEX specification

International NAVTEX (NAVigational TelEX)

service means the co-ordinated broadcast and auto-

matic reception on the frequency 518 kHz of mari-

time safety information (MSI) by means of Narrow

Band Direct Printing (NBDP-FEC) telegraphy. The

operational and technical characteristics of the

NAVTEX system are contained in Recommendation

ITU-R M.540. Performance standards for shipborne

narrow-band direct-printing equipment are laid

down in IMO Assembly resolution A.525(13).

The principal features of NAVTEX service are as

follows:

− the service uses a single frequency (518 kHz) on

which coast stations transmit information in Eng-

lish on a time-sharing basis to prevent mutual in-

terference; all necessary information is contained

in each transmission;

− the power of each coast station transmitter is reg-

ulated so as to avoid the possibility of interfer-

ence between coast stations; Navtex transmis-

sions provide a range of about 250 to 400 nautical

miles;

− dedicated Navtex receivers are used on the board

of the ships; they have the ability to select mes-

sages to be printed, according to a technical code

(B1B2B3B4) which appears in the preamble of

each message.

3 LAST DECADE GMDSS MODIFICATION

The last decade modification of the GMDSS has

concerned both technical and regulatory issues.

3.1 Technical modification of GMDSS

The most important GMDSS modification has con-

cerned the Inmarsat. In 1999, Inmarsat became the

first intergovernmental organisation to transform in-

to a private company and, in 2005, was floated on

the London Stock Exchange. It caused that at present

Inmarsat is recognised as a leader in mobile satellite

communication field.

Inmarsat Fleet service provides both ocean-

going and coastal vessels with comprehensive voice,

fax and data communications. At present the Fleet

range of services includes:

− Fleet 77

− Fleet 55

− Fleet 33

Inmarsat Fleet 77 has been introduced in 2002,

and Inmarsat Fleet 55 and 33 in 2003.

Inmarsat Fleet's high-quality Mobile ISDN and

cost-effective IP-based Mobile Packet Data Services

offer unparallel connectivity for access to e-mail and

the Internet, weather updates, video conferencing

and vessel monitoring systems.

Fleet 33 offers global voice as well as fax and a

choice of data communications at up to 9.6kbps.

456

Fleet 55 offers global voice and high-speed fax

and data services at up to 64kbps.

Fleet 77 is Inmarsat's most advanced maritime

service, providing global voice and high-speed fax

and data services at up to 128kbps. It fully supports

the GMDSS and includes advanced features such as

emergency call prioritization, as stipulated by IMO

Resolution A.1001 (25). Fleet F77 also helps meet

the requirements of the International Ship and Port

Facility Security (ISPS) code, which enables the

cost-effective transfer of electronic notices of arri-

val, crew lists, certificates and records.

Inmarsat Fleet series are recommended for the

applications showed in Table 1.

Table 1. Applications of Inmarsat Fleet series

__________________________________________________

Fleet 33 Fleet 55 Fleet 77

__________________________________________________

Data transfer + + +

Internet + + +

E-mail and messaging + + +

Fax + + +

SMS text + + +

Voice + + +

Crew calling + + +

Encryption - - +

Videoconferencing - - +

Remote monitoring + + +

Weather updates + + +

Telemedicine + + +

GMDSS functions - - +

__________________________________________________

Because Fleet 77 is IP compatible, it supports an

extensive range of commercially available off-the-

shelf software, as well as specialized maritime and

business applications. Fleet 77 also ensures cost-

effective communications by offering the choice of

Mobile ISDN or MPDS channels at speeds of up to

128kbps.

FleetBroadband is Inmarsat's next generation of

maritime services delivered via the Inmarsat-4 satel-

lites. It is commercially available since the second

half of 2007. The service is designed to provide the

way forward for cost-effective, high-speed data and

voice communications (Table 2).

Users have the choice of two products (FB250

and FB500). Both use stabilized, directional anten-

nas, which vary in size and weight. The above deck

antennas are smaller than other Fleet products.

Table 2. FleetBroadband performance capabilities

__________________________________________________

FB250 FB500

__________________________________________________

Data

Standard IP Up to 284kbps Up to 432kbps

Streaming IP 32, 64, 128kbps 32, 64, 128, 256kbps

ISDN – 64kbps

Voice 4kbps and digital 3.1kHz audio

Fax Group 3 fax via 3.1kHz audio

SMS Standard 3G (up to 160 characters)

Antenna

Diameter from 25cm 57cm

Height from 28cm 68cm

Weight from 2.5kg 18kg

__________________________________________________

FleetBroadband supports an extensive range of

commercially available, off-the-shelf software, as

well as specialized user applications. It is ideal for:

− Email and webmail

− Real-time electronic chart and weather updates

− Remote company intranet and internet access

− Secure communications

− Large file transfer

− Crew communications

− Vessel/engine telemetry

− SMS and instant messaging

− Videoconferencing

− Store and forward video.

It should be also noted that Inmarsat E service

ceased to be supporting GMDSS in 2006 and In-

marsat A service – in 2007.

In the same time, instead of the Inmarsat E ser-

vice, the new Cospas-Sarsat Geostationary Search

and Rescue System (GEOSAR) has been introduced

as completion of the Low-altitude Earth Orbit Sys-

tem (LEOSAR). These two Cospas-Sarsat systems

(GEOSAR and LEOSAR) create the complementary

system assists search and rescue operations (SAR).

As the result of the hard work of International

Maritime Organization (IMO) other two new sys-

tems have been introduced:

− Ship Security Alert System – SSAS (in 2004),

− Long-Range Identification and Tracking of ships

– LRIT (in 2009).

Although the above mentioned systems are not a

part of the GMDSS, in the direct way they use its

communication means.

At the end it’s worth to note that the International

Cospas-Sarsat System has ceased satellite processing

of 121.5/243 MHz beacons on 1 February 2009 and

that on 1.01.2010 AIS-Search and Rescue Transmit-

ter (AIS-SART) have been introduced as well.

3.2 Regulatory modification of GMDSS

At a regulatory level a modification of the GMDSS

is coordinated by two international organizations:

International Maritime Organization (IMO) and In-

ternational Telecommunication Union (ITU).

IMO modifications are mainly concerning to the

amendments to Chapter IV of the International Con-

vention for the Safety of Life At Sea (SOLAS) and

to the IMO resolutions.

From the Radiocommunication point of view, the

most important modification was adoption by IMO

457

of Resolution A.1001(25) dated 29.11.2007 on Cri-

teria for the Provision of Mobile Satellite Communi-

cation Systems in the GMDSS and revision of Chap-

ter IV of IMO SOLAS Convention extends the

International Mobile Satellite Organization (IMSO)

oversight to GMDSS Services provided by any sat-

ellite operator which fits criteria.

ITU modifications are mainly concerning to the

amendments to Radio Regulations. These amend-

ments were adopted by two Word Radiocommunica-

tion Conferences (WRC).

The first World Radiocommunication Conference

took place in 2003 (WRC-03) and in the field of

maritime radiocommunication it took up following

main issues:

− to consider Appendix 13 and Resolution 331

(Rev.WRC-97) with a view to their deletion and,

if appropriate, to consider related changes to

Chapter VII and other provisions of the Radio

Regulations, as necessary, taking into account the

continued transition to an introduction of the

Global Maritime Distress and Safety System

(GMDSS) (Agenda Item 1.9);

− to consider the results of studies, and take neces-

sary actions, relating to exhaustion of the mari-

time mobile service identity numbering resource

(Resolution 344 (WRC-97)) (Agenda Item

1.10.1);

− to consider the results of studies, and take neces-

sary actions, relating to shore-to-ship distress

communication priorities (Resolution 348

(WRC-97)) (Agenda Item 1.10.2);

− to consider measures to address harmful interfer-

ence in the bands allocated to the maritime mo-

bile and aeronautical mobile (R) services, taking

into account Resolutions 207 (Rev.WRC-2000)

and 350 (WRC-2000), and to review the frequen-

cy and channel arrangements in the maritime MF

and HF bands concerning the use of new digital

technology, also taking into account Resolution

347 (WRC-97) (Agenda Item 1.14).

The second Word Radiocommunication Confer-

ence took place in 2007 (WRC-07) and the main

maritime radiocommunication items were as follows

(ITU, 2008):

− taking into account Resolutions 729 (WRC-97),

351 (WRC-03) and 544 (WRC-03), to review the

allocations to all services in the HF bands be-

tween 4 MHz and 10 MHz, excluding those allo-

cations to services in the frequency range 7 000-

7 200 kHz and those bands whose allotment plans

are in Appendices 25, 26 and 27 and whose chan-

nelling arrangements are in Appendix 17, taking

account the impact of new modulation tech-

niques, adaptive control techniques and the spec-

trum requirements for HF broadcasting (Agenda

Item 1.13);

− to review the operational procedures and re-

quirements of the Global Maritime Distress and

Safety System (GMDSS) and other related provi-

sions of the Radio Regulations, taking into ac-

count Resolutions 331 (Rev.WRC-03) and 342

(Rev.WRC-2000) and the continued transition to

the GMDSS, the experience since its introduc-

tion, and the needs of all classes of ships (Agenda

Item 1.14);

− to consider the regulatory and operational provi-

sions for Maritime Mobile Service Identities

(MMSIs) for equipment other than shipborne

mobile equipment, taking into account Resolu-

tions 344 (Rev.WRC-03) and 353 (WRC-03)

(Agenda Item 1.16).

4 FUTURE OF GMDSS

In Author’s opinion, the future of the GMDSS is

closely connected with the development of the e-

navigation project and with a role of the GMDSS in

this process.

For realizing the full potential of e-navigation, the

following three fundamental elements should be in

place (Korcz, 2009):

1 Electronic Navigation Chart (ENC) coverage of

all navigational areas;

2 a robust electronic position-fixing system (with

redundancy); and

3 an agreed infrastructure of communications to

link ship and shore.

It is envisaged that a data communication net-

work will be one of the most important parts of the

e-navigation strategy plan.

In order to realize efficient and effective process

of data communication for e-navigation system, the

existing radio communication equipment on board

(GMDSS), as well as new radio communication sys-

tems should be recognized.

The above mentioned GMDSS MF, HF and VHF

equipment and systems (Fig. 1) can be also used as a

way of data communication for the e-navigation sys-

tem, provided that this equipment will be technically

improved by means of:

− digitization of the analogue communication MF,

HF and VHF channels;

− application of high-speed channel to GMDSS;

− utilization of SDR (Software Defined Radio)

technology;

− adaptation of IP (Internet Protocol) technology to

GMDSS;

− integration of user interface of GMDSS equip-

ment; and

− any other proper technology for GMDSS im-

provement.

458

This technical improvement of GMDSS equip-

ment may mean the potential replacement of the

conventional equipment by virtual one.

In this approach to development of e-navigation

it is very important that the integrity of GMDSS

must not be jeopardized.

With respect to the radiocommunication aspects

required for e-navigation (modernization process),

the following should be taken into account as well :

− autonomous acquisition and mode switching;

− common messaging format;

− sufficiently robust;

− adequate security (e.g. encryption);

− sufficient bandwidth (data capacity);

− growth potential;

− automated report generation;

− global coverage (could be achieved with more

than one technology).

The next ITU Word Radiocommunication Con-

ference will take place in 2012 (WRC-12) and the

main maritime radiocommunication items which

will be discussed are following (COMSAR 15,

2011):

− to revise frequencies and channelling ar-

rangements of Appendix 17 to the Radio

Regulations, in accordance with Resolution 351

(Rev.WRC-07), in order to implement new digi-

tal technologies for the maritime mobile service;

and

− to examine the frequency allocation requirements

with regard to operation of safety systems for

ships and ports and associated regulatory pro-

visions, in accordance with Resolution 357

(WRC-07).

From among other announcements concerning the

future GMDSS modification the following should be

given:

− the new Arctic NAVAREAs/METAREAs are ex-

pected to be transitioned to Full Operational Ca-

pability (FOC) on 1 June 2011;

− the new Arctic NAVAREAs/METAREAs are ex-

pected to be transitioned to Full Operational Ca-

pability (FOC) on 1 June 2011;

− Inmarsat Global Limited (Inmarsat) has informed

of its intention to close the Inmarsat-B Service

from 31 December 2014;

− the new Cospas-Sarsat MEOSAR system will be

probably full operational on 2018.

5 CONCLUSIONS

Twelve years have passed since the time when the

Global Maritime Distress and Safety System

(GMDSS) became introduced. Planning for the

GMDSS started more than 25 years ago, so elements

of it have been in place for many years.

There have been numerous advances in the use of

maritime radiocommunication to maritime safety,

security and environmental protection during this

period. But now there are some obsolete GMDSS

equipment and systems or the ones that have seldom

or never been used in practice.

On the other hand there are a lot of new digital

and information technologies.

Not only in the Author’s opinion, the time is ripe

to start the wide discussion on what the real condi-

tion and needs of the marine radiocommunication

are, in particular with reference to the current dis-

cussion on the e-navigation strategy.

During this work it is necessary first to identify

real user needs and secondly to realize that the mod-

ernization of the maritime radiocommunication

should not be driven by technical requirements. In

addition, it is necessary to ensure that man-machine-

interface and the human element will be taken into

account including the training of personnel.

The lessons learnt from the original development

and operation of GMDSS should be taken into ac-

count in the modification of GMDSS as well.

Furthermore a systematic process is needed to re-

view and modify the GMDSS to ensure it remains

modern and fully responsive to changes in require-

ments and evolutions of technology and it will meet

the expected e-navigation requirements.

For assuming this process a mechanism for con-

tinuous evolution of the GMDSS in a systematic

way should be created.

At the beginning, for synchronization of this

work a work plan for the process of the review and

modernization of the GMDSS should be established,

taking into account the above mentioned issues.

A framework document which defines timescales

of this work should be recognized as well.

And finally it should be noted that a key to the

success of the review and modernization process is

not only that the work is completed on time, but also

that it has the flexibility to implement changes ahead

of schedule.

In the above context further it should be noted

that the Sub-Committee on radiocommunications

and search and rescue (COMSAR) since it’s last ses-

sion in 2010 (COMSAR 14) has started work on is-

sue the Scoping Exercise to establish the need for a

review of the elements and procedures of the

GMDSS. Finish of this process is planed on COM-

SAR 16 in 2012 and it is expected that as the result

of this work a lot of answers will be given on the fu-

459

ture process of the review and modernization of the

GMDSS (COMSAR 14, COMSAR 15).

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