Global Maritime Distress & Safety

• The Global Maritime Distress & Safety System (GMDSS) was created after the invention of the radio at the end of the 19th century
• Ships used Morse code for distress and safety telecommunications, with the first use in 1844
• After the Titanic sank in 1912, legislation required ships to have Morse code radiotelegraph equipment and listen to a common frequency for distress calls
• The International Telecommunications Union (ITU) followed suit, requiring ships of all nations to use Morse code for distress calls
• Morse code distress calling required skilled radio operators to spend many hours listening to a specific radio frequency
• The range on the medium-frequency (MF) distress band (500 kHz) was limited, as also the amount of traffic Morse signals could carry

The Development of GMDSS

• The International Maritime Organization (IMO) started improving maritime distress and safety communications in the mid-1970s
• In 1979, the International Convention on Maritime Search and Rescue called for a global search and rescue plan
• The IMO developed the GMDSS to provide communication support for the search and rescue plan
• The GMDSS is based on satellite and terrestrial radio services and changed international distress communications from ship-to-ship to ship-to-shore
• The GMDSS replaced the mandatory requirement for Morse code communication by commercial vessels
• The GMDSS provides automatic distress alerting and locating and requires ships to receive broadcasts of maritime safety information
• In 1988, the Safety of Life at Sea Convention (SOLAS) was amended, requiring ships to fit GMDSS equipment
• Ships were required to carry NAVTEX and satellite EPIRBs by 1 August 1993, and all other GMDSS equipment by 1 February 1999
• U.S. ships were allowed to fit GMDSS in place of Morse telegraphy equipment by the Telecommunications Act of 1996
• The GMDSS consists of several systems and can reliably perform functions like alerting, search and rescue coordination, locating, 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

Features of GMDSS

• The GMDSS is the internationally recognized distress and radio communication safety system for ships
• It is an automated ship-to-shore system using satellites and digital selective calling (DSC) technology
• The GMDSS is mandated for all ships by the IMO
• The GMDSS provides worldwide ship-to-shore alerting and simplifies radio operations allowing alerts to be sent by two simple actions
• It ensures redundancy of communications, enhances search and rescue, minimizes unanticipated emergencies at sea, and eliminates reliance on a single person for communications
• It requires at least two licensed GMDSS radio operators and two maintenance methods to ensure distress communications capability at all times

Sea Areas

• GMDSS uses four coverage areas to cover the sea areas of the world for distress watchkeeping, namely A1, A2, A3, and A4
• Sea Area A1: Within radiotelephone range of at least one VHF/DSC coast station (about 20-30 NM)
• Sea Area A2: Within MF range of a coast station fitted with DSC (about 150 miles)
• Sea Area A3: Covered by the Inmarsat Satellite System (excluding A1 and A2 areas)
• Sea Area A4: Polar regions not covered by the above

GMDSS Component Systems

• The GMDSS consists of separate systems being implemented in a coordinated manner
• The COSPAS-SARSAT System is an international satellite-based search and rescue system, established by Canada, France, the U.S., and Russia
• These countries codeveloped a 406 MHz satellite emergency position-indicating radiobeacon (EPIRB), an element of the GMDSS designed to operate with the COSPAS-SARSAT system
• EPIRBs are required on SOLAS ships, commercial fishing vessels, and other ships and are designed to transmit to a rescue coordination center a vessel identification and an accurate location of the vessel from anywhere in the world

Emergency Position Indicating RadioBeacon (EPIRB)

• Every boat that goes offshore beyond reliable VHF radio range should carry an EPIRB
• Original models operated on two frequencies: 121.5 MHz (emergency channel for civilian planes) and 243.0 MHz (guard channel for military aircraft)
• Aircraft detecting these EPIRBs reported to the airway control authorities
• Equipment on orbiting satellites of the COSPAS-SARSAT system could relay EPIRB signals when the satellite could "see" both the EPIRB and a ground terminal simultaneously
• The beacon's position was determined by multiple reports from aircraft and/or orbiting satellites
• It took 4 to 6 hours (sometimes up to 12 hours) to determine a position and initiate rescue efforts, with location usually within 12 to 15 miles (22 to 28 km)
• EPIRBs were divided into Class A (floatfree, automatic activation) and Class B (manually activated)
• First-generation EPIRBs suffered from interference and had a very high incidence of false alarms
• Processing signals from Class A and B units by the COPAS-SARSAT system was discontinued on 1 February 2009
• Now, only 406 MHz signals are monitored

Second Generation EPIRBs

• Advances in technology led to the development of "406" EPIRBs, operating at 406.0 MHz
• These signals are picked up by orbiting satellites of COSPAS-SARSAT, transmitted to a ground station, and passed on to rescue authorities
• Distress signals are stored by the satellite and retransmitted when a ground station is in range
• Distress signals can also be received and relayed by GEOS weather satellites and other geostationary satellites of the GEOSAR system
• When COSPAS-SARSAT satellites are used, position is determined by the Doppler effect
• Position can be determined within 1 to 3 miles (2 to 5 km) and may take 1 to 2 hours
• If signals are detected by a GEOSAR satellite, an immediate distress alert is provided, but no position information is given
• Each 406 EPIRB transmits a unique registration number for identification
• Each unit is entered into a database that provides vital information on the vessel
• Purchasers of 406 EPIRBs are legally required to register them with penalties for failing to comply

Personal Locator Beacon (PLB)

• A Personal Locator Beacon (PLB) serves the same needs for a boater as an EPIRB but meant to be associated with an individual
• PLBs are smaller and lighter, transmitting the same 406 and 121.5 MHz signals with identification specific to that unit
• Some models may have an input for GPS position data, and never models have internal GPS included
• PLBs do not have a strobe light and will not function in that situation, with intended operation for a shorter period than an EPIRB
• The FCC authorized the sale and use of PLBs in the United States as of 1 July 2003, and these units must be registered

EPIRB Registration

• EPIRB registration is for two years only, requiring re-registration, and any changes must be reported
• No fees are required for registration
• Available in Category I (float-free, automatic activation) and Category II (manual activation); both have a 121.5 MHz beacon and strobe light
• Category II units range from $500 to $650, with Category I models $50 to $100 more expensive
• A model of a 406 EPIRB with a connection for position data from an onboard GPS receiver as well as a 406 EPIRB with an internal GPS receiver have been created
• The vessel's position is continually updated and stored in the EPIRB every 20 minutes
• Cost of an EPIRB with GPS interconnect capability is slightly than that of a standard 406 EPIRB, about $550 to $600
• A GPIRB, with integral GPS receiver, is about $750 to $800
• The distress location is clearly established to less than a half mile (1 km)

EPIRB Use and Maintenance

• An activated EPIRB must be left on
• Testing must be strictly limited to the unit's manual conditions
• The only maintenance is the battery replacement at intervals specified by the unit's manual

NAVTEX

• NAVTEX is an international, automated system for distributing maritime navigational warnings, weather forecasts, search and rescue notices, and safety information to ships
• A NAVTEX receiver is installed in the pilot house and checks each incoming message to see if it has been received or if not relevant
• NAVTEX receivers print messages on a roll of adding-machine-size paper
• Certain types of messages can be set to "non-print" and recent models use an LCD screen with optional printing
• A new ship receives many previously broadcast messages for the first time, while others that have already received it do not receive it again
• A person does not need to be present during a broadcast
• Transmitting stations operate at scheduled times on 518 kHz, with NAVTEX reception extending 200 to 400 nautical miles

Inmarsat

• Inmarsat satellite systems operated by the International Mobile Satellite Organization are important elements of the GMDSS
• Inmarsat A, B, M, and Fleet 77, Fleet 55, and Fleet 33 systems provide ship-shore, ship-ship, and shore-ship telephone, telex, and high-speed data services, including distress priority telephone and telex service
• Inmarsat M and Mini-M equipment is small and lighter and voiceless Inmarsat C and Mini-C provide ship-shore, shore-ship, and ship-ship store-and-forward data and telex messaging
• They also have the capability for sending preformatted distress messages to a rescue coordination center, and the SafetyNET service
• SafetyNET works similarly to NAVTEX in areas outside NAVTEX coverage
• Inmarsat C and Mini-C equipment is small and lighter than Inmarsat A, B, or Fleet F77
• Inmarsat A, B, and Fleet F77 and F55 ship earth stations require large gyrostabilized antennas, while the antenna size of the Fleet 33, Inmarsat C, and Mini-C is smaller
• Inmarsat also operates an EPIRB system, the Inmarsat E and E+, similar to that operated by COSPAS-SARSAT
• Fleet F33 provides voice, fax, and data for smaller vessels
• Combined meteorological observations and AMVER reports can be sent to both the USCG AMVER Center and NOAA, using an Inmarsat C ship-earth station, at no charge
• Inmarsat C equipment have an integral satellite navigation receiver, or be externally connected to a satellite navigation receiver

High-Frequency Communications

• The GMDSS includes HF radiotelephone and radiotelex equipment, with calls initiated by digital selective calling
• Worldwide broadcasts of maritime safety information are made on HF narrow-band direct printing channels
• The Coast Guard improved high-frequency (HF) ship-shore radio safety services to the maritime community, as well as narrow-band direct-printing broadcasts

SART

• The GMDSS installation on ships includes one or more search-and-rescue radar transponders (SART)
• They are used to locate survival craft or distressed vessels by creating a series of dots on a rescuing ship's X-band (3 cm) radar display
• The detection range depends on the height of the ship's radar mast and the height of the SART, normally about eight nautical miles
• A marine radar may not detect a SART even within this range