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GMDSS

- Information About GMDSS is Provided by the United States Coast Guard.

An Overview of the Global Maritime Distress & Safety System

Since the invention of radio at the end of the 19th Century, ships at sea have relied on Morse code, invented by Samuel Morse and first used in 1844, for distress and safety telecommunications. The need for ship and coast radio stations to have and use radiotelegraph equipment, and to listen to a common radio frequency for Morse encoded distress calls, was recognized after the sinking of the liner Titanic in the North Atlantic in 1912. The U.S. Congress enacted legislation soon after, requiring U.S. ships to use Morse code radiotelegraph equipment for distress calls. The International Telecommunications Union (ITU), now a United Nations agency, followed suit for ships of all nations. Morse encoded distress calling has saved thousands of lives since its inception almost a century ago, but its use requires skilled radio operators spending many hours listening to the radio distress frequency. Its range on the medium frequency (MF) distress band (500 kHz) is limited, and the amount of traffic Morse signals can carry is also limited.

Over fifteen years ago the International Maritime Organizatyon (IMO), a United Nations agency specializing in safety of shipping and preventing ships from polluting the seas, began looking at ways of improving maritime distress and safety communications. In 1979, a group of experts drafted the International Convention on Maritime Search and Rescue, which called for development of a global search and rescue plan. This group also passed a resolution calling for development by IMO of a Global Maritime Distress and Safety System (GMDSS) to provide the communication support needed to implement the search and rescue plan. This new system, which the world's maritime nations, including the United States, are implementing, is based upon a combination of satellite and terrestrial radio services, and has changed international distress communications from being primarily ship-to-ship based to ship-to-shore (Rescue Coordination Center) based. It spelled the end of Morse code communications for all but a few users, such as Amateur Radio. The GMDSS provides for automatic distress alerting and locating in cases where a radio operator doesn't have time to send an SOS or MAYDAY call, and, for the first time, requires ships to receive broadcasts of maritime safety information which could prevent a distress from happening in the first place. In 1988, IMO amended the Safety of Life at Sea (SOLAS) Convention, requiring ships subject to it fit GMDSS equipment. Such ships were required to carry NAVTEX and satellite EPIRBs by 1 August 1993, and had to fit all other GMDSS equipment by 1 February 1999. US ships were allowed to fit GMDSS in lieu of Morse telegraphy equipment by the Telecommunications Act of 1996.

The GMDSS consists of several systems, some of which are new, but many of which have been in operation for many years. The system will be able to reliably perform the following functions: alerting (including position determination of the unit in distress), search and rescue coordination, locating (homing), maritime safety information broadcasts, general communications, and bridge-to-bridge communications. Specific radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. The system also provides redundant means of distress alerting, and emergency sources of power.
The GMDSS consists of many separate systems which are being implemented in a coordinated and agreed-upon manner. Some of these systems are discussed below:

GMDSS Systems:

The COSPAS-SARSAT system.
COSPAS-SARSAT is an international satellite-based search and rescue system, established by Canada, France, the U.S.A., and Russia. These four countries jointly helped develop a 406 MHz satellite emergency position-indicating radiobeacon (EPIRB), an element of the GMDSS designed to operate with COSPAS-SARSAT system. These automatic-activating EPIRBs, now required on SOLAS ships, commercial fishing vessels, and other ships, are designed to transmit to a rescue coordination center a vessel identification and an accurate location of the vessel from anywhere in the world.

NAVTEX
NAVTEX is an international, automated system for instantly distributing maritime navigational warnings, weather forecasts and warnings, search and rescue notices and similar information to ships. A small, low-cost and self-contained "smart" printing radio receiver installed in the pilot house of a ship or boat checks each incoming message to see if it has been received during an earlier transmission, or if it is of a category of no interest to the ship's master. If it is a new and wanted message, it is printed on a roll of adding-machine size paper; if not, the message is ignored. A new ship coming into the area will receive many previously-broadcast messages for the first time; ships already in the area which had already received the message won't receive it again. No person needs to be present during a broadcast to receive vital information.

Inmarsat.
Satellite systems operated by the International Mobile Satellite Organization (Inmarsat), are also important elements of the GMDSS. Three types of Inmarsat ship earth station terminals are recognized by the GMDSS: the Inmarsat A, B and C. The Inmarsat A and B, an updated version of the A, provide ship/shore, ship/ship and shore/ship telephone, telex and high-speed data services, including a distress priority telephone and telex service to and from rescue coordination centers. The Inmarsat C provides ship/shore, shore/ship and ship/ship store-and-forward data and telex messaging, the capability for sending preformatted distress messages to a rescue coordination center, and the SafetyNET service. The Inmarsat C SafetyNET service is a satellite-based worldwide maritime safety information broadcast service of high seas weather warnings, NAVAREA navigational warnings, radionavigation warnings, ice reports and warnings generated by the USCG-conducted International Ice Patrol, and other similar information not provided by NAVTEX. SafetyNET works similarly to NAVTEX in areas outside NAVTEX coverage.

Inmarsat C equipment is relatively small and lightweight, and costs much less than an Inmarsat A or B. Inmarsat A and B ship earth stations require relatively large gyro-stabilized antennas; the antenna size of the Inmarsat C is much smaller. Inmarsat also operates an EPIRB system, the Inmarsat L, which is similar to that operated by COSPAS-SARSAT.

Under a cooperative agreement with the National Oceanic and Atmospheric Administration (NOAA), combined meteorological observations and AMVER reports can now be sent to both the USCG AMVER Center, and NOAA, using an Inmarsat C ship earth earth station, at no charge. There is also no charge to register for this service and to receive the necessary Inmarsat C software. For more information, refer to the NOAA Shipboard Environmental (data) Acquisition System, or SEAS.

We strongly urge that Inmarsat C equipment have an integral satellite navigation receiver, or be externally connected to a satellite navigation receiver. That connection will ensure accurate location information to be sent to a rescue coordination center if a distress alert is ever transmitted.

High Frequency
The GMDSS includes HF radiotelephone and radio telex (narrow-band direct printing) equipment, with calls initiated by digital selective calling. Worldwide broadcasts of maritime safety information are also made on HF narrow-band direct printing channels.
To meet these GMDSS requirements, the Coast Guard has improved high frequency (HF) ship-shore radio safety services from our Communication Stations to the maritime community, as well as narrow-band direct printing broadcasts.

Search and Rescue Radar Transponders (SARTs).
The GMDSS installation on ships include one or more search and rescue radar transponders, devices which are used to locate survival craft or distressed vessels by creating a series of dots on a rescuing ship's 3 cm 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 about eight nautical miles. Note that a marine radar may not detect a SART even within this distance, if the radar settings are not optimized for SART detection.

Digital Selective Calling
The IMO also introduced digital selective calling (DSC) on VHF, MF and HF maritime radios as part of the GMDSS system. DSC is primarily intended to initiate ship/ship, ship/shore, and shore/ship radiotelephone and MF/HF radiotelex calls. DSC calls can also be made to individual ships or groups of ships. DSC distress alerts, which consist of a preformatted distress message, are used initiate emergency communications with ships and rescue coordination centers. When fully implemented, DSC will eliminate the need for persons on a ship's bridge or on shore to continuously guard radio receivers on voice radio channels, including VHF channel 16 (156.8 MHz) and 2182 kHz now used for distress, safety and calling. A listening watch aboard GMDSS-equipped ships on 2182 kHz ended on 1 February 1999, and on VHF channel 16 is scheduled to end on 1 February 2005.
We urge that the DSC-equipped VHF and MF/HF radios be externally connected to a satellite navigation receiver. That connection will ensure accurate location information is sent to a rescue coordination center if a distress alert is ever transmitted. FCC regulations actually require that ship's position be manually entered into the radio every four hours on ships required to carry GMDSS equipment, while that ship is underway (47 CFR 80.1073).

Once SOLAS ships are allowed to disband watchkeeping on VHF and MF radiotelephone channels, other ships are going to need DSC-equipped radios to contact these ships, particularly in a passing situation, especially when outside U.S. waters. We believe VHF, MF and HF radiotelephone equipment carried on ships should include a DSC capability as a matter of safety. To achieve this, the FCC requires that all new VHF and MF/HF maritime radiotelephones type accepted after June 1999 to have at least a basic DSC capability.
VHF digital selective calling also has other capabilities beyond those required for the GMDSS. The Coast Guard uses this system to track vessels in Prince William Sound, Alaska, Vessel Traffic Service. IMO and the USCG also plan to require ships carry a Universal Automatic Identification System, which will be DSC-compatible. Countries having a GMDSS A1 Area will be able to identify and track AIS-equipped vessels in its waters without any additional radio equipment.

A DSC-equipped radio cannot be interrogated and tracked unless that option was included by the manufacturer, and unless the user configures it to allow tracking.

U.S. shore-based radio stations currently exist to support every element of the GMDSS, except for digital selective calling. The United States currently has no declared A1 Sea Areas or A2 Sea Areas, but plans to eventually have both areas in place.

Use of GMDSS for Routine Telecommunications

GMDSS telecommunications equipment should not be reserved for emergency use only. The International Maritime Organization in COMSAR Circ.17 encourages mariners to use that equipment for routine as well as safety telecommunications.

Who has to Comply with the GMDSS?

SOLAS Ships
Ships subject to the Chapter IV of the Safety of Life at Sea (SOLAS) Convention have to fit GMDSS equipment. These include all ships engaged on international voyages except:

Cargo ships less than 300 gross tonnage,
Ships of war and troopships,
Ships not propelled by mechanical means,
Wooden ships of primitive build,
Pleasure yachts not engaged in trade,
Fishing vessels, and
Ships being navigated within the Great Lakes of North America.

U.S. Communications Act Ships
Ships subject to Title II Part II and Part III of the Communications Act of 1934, as amended have to fit GMDSS equipment under FCC Regulation 47 CFR 80 Subpart W. These include all ships, including fishing vessels, to be navigated in the open sea outside of a harbor or port, except:

Ships other than passenger vessels less than 300 gross tonnage,
Passenger ships having six passengers or less,
U.S. government ships,
Yachts of less than 600 gross tons,
Vessels in tow,
Ships navigating solely on any bays, sounds, rivers or protected waters within the U.S.,
Ships being navigated within the Great Lakes of North America, and
Small passenger ships meeting the requirements of 47 CFR 80 Subpart S.

Note that on 20 November 1998, the FCC has waived certain GMDSS rules applicable to fishing vessels and small passenger vessels.
Mobile Offshore Drilling Units (MODUs)
Mobile Offshore Drilling Units have to fit GMDSS equipment if they are self propelled, or if they are required to meet the International Maritime Organization's MODU Code.

GMDSS Brochure

The new edition of the brochure The Future in Marine Radio Communications - GMDSS is now available. The brochure, jointly produced by the U.S. Coast Guard and the National GMDSS Implementation Task Force, is written primarily for operators of small commercial vessels, but intended for anyone interested in the GMDSS or marine communications. The new edition reflects changes to GMDSS regulations made by the IMO Maritime Safety Committee in 1997.
For a copy of the brochure, send a self-addressed envelope at least 4" X 9" to the address at the bottom of this page, indicating whether you wish the commercial or recreational vessel version. Since copies are limited, please describe your need if you wish more than a few copies.

Global Maritime Distress and Safety System Sea Areas

GMDSS sea areas serve two purposes: to describe areas where GMDSS services are available, and to define what GMDSS ships must carry. Prior to the GMDSS, the number and type of radio safety equipment ships had to carry depended upon its tonnage. With GMDSS, the number and type of radio safety equipment ships have to carry depend upon the areas in which they travel. GMDSS sea areas are defined by governments.

In addition to equipment listed below, all GMDSS-regulated ships must carry a satellite EPIRB, a NAVTEX receiver (if they travel in any areas served by NAVTEX), an Inmarsat-C SafetyNET receiver (if they travel in any areas not served by NAVTEX), a DSC-equipped VHF radiotelephone, two or more VHF handhelds, and a search and rescue radar transponder (SART).

Sea Area A1
An area within the radiotelephone coverage of at least one VHF coast station in which continuous digital selective calling (ch70) alerting and radiotelephony services are available, as defined by the International Maritime Organization.

The United States presently has no A1 Sea Areas. Establishment of an A1 Sea Area in the U.S. is expected to depend upon approval and funding of the National Distress System Modernization Project.

Sea Area A2
An area, excluding Sea Area Al, within the radiotelephone coverage of at least one MF coast station in which continuous DSC (2187.5 kHz) alerting and radiotelephony services are available, as defined by the International Maritime Organization. GMDSS-regulated ships travelling this area must carry a DSC-equipped MF radiotelephone in addition to equipment required for Sea Area A1.

The United States presently has no declared A2 Sea Areas. The US Coast Guard has installed and is operating seven A2 Sea Area-capable coast stations, but those stations do not yet provide continuous coverage. Installation of DSC at most additional A2 Sea Area-capable coast stations is on hold, pending an update in DSC equipment.

Charts below of GMDSS Sea Areas A1 and A2 are from GMDSS/Circ.8 dated 2 February 1999, courtesy the International Maritime Organization. Solid lines represent actual service areas and dashed lines planned service areas.

<<<link to site with following picture>>>A1 and A2 Areas in North and South America

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<<<link to site with following picture>>>A1 and A2 Areas in Europe and Western Africa

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<<<link to site with following picture>>>A1 and A2 Areas in Eastern Africa and India

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<<<link to site with following picture>>>A1 and A2 Areas in Asia and the West Pacific

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Sea Area A3
An area, excluding sea areas Al and A2, within the coverage of an INMARSAT geostationary satellite in which continuous alerting is available. Ships travelling this area must carry either an Inmarsat A, B or C ship earth station, or a DSC-equipped HF radiotelephone/telex, in addition to equipment required for an A1 and A2 Area.

<<<link to site with following picture>>>A3 – INMARSAT Area
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Sea Area A4
The area outside that covered by areas A1, A2 and A3 is called Sea Area A4 Area. Ships traveling these polar regions must carry a DSC-equipped HF radiotelephone/telex, in addition to equipment required for areas A1 and A2.

GMDSS Radio Equipment Required for U.S. Coastal Voyages
Presently, until an A1 or A2 Sea Area is established, GMDSS-mandated ships operating off the U.S. coast must fit to Sea Areas A3 (or A4) regardless of where they operate. U.S. ships whose voyage allows them to always remain within VHF channel 16 coverage of U.S. Coast Guard stations may apply to the Federal Communications Commission for an individual waiver to fit to Sea Area A1 requirements. Similarly, those who remain within 2182 kHz coverage of U.S. Coast Guard stations may apply for a waiver to fit to Sea Area A2 requirements.

Mail all inquiries to:
Commandant (G-SCT-2)
U.S. Coast Guard
Washington DC 20593

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