The Global Maritime Distress and Safety System is the global emergency and safety system that came into force on 1 February 1999. The system applies to all ships larger than 300 GRT. as well as passenger ships in international traffic.
GMDSS is based on satellite and digital communication and is a replacement for the old analog system, which operated on 2182 kHz and VHF channel 16. The cornerstones of the system are built on requirements that follow from the sea areas named:
A1 - covered by VHF DSC
A2 - covered by MF DSC
A3 - covered by Inmarsat and Iridium
A4 - everything outside the above areas. In theory, it is the sea areas north of approx. 76º north latitude and south of approx. 76º south latitude. Iridium will cover the area.
Medium wave DSC is a digital calling system that is used both commercially and as an emergency and security system.
In Greenland, A2 sea areas have been established covered by selected transmitters on medium-wave DSC. The Greenlandic DSC system only functions as an emergency and safety system on the frequency 2187.5 kHz. The A2 sea area broadly covers the coastline from north of Upernavik to the coast north of Tasiilaq at a distance of up to approx. 300 nautical miles from the coast.
Like MF DSC, VHF DSC is built as a digital system. The system is used for emergency and safety systems, but also commercially.
In GMDSS, the Inmarsat system is an emergency and safety system that covers the globe between approx. 76º north latitude and approx. 76º south latitude.
The range is limited by Inmarsat's geostationary satellites.
There is a wide range of ship earth stations and land station stations to cover shipping needs for communication.
However, the Inmarsat system can also be used commercially for calls and telegrams.
You can find further information about Inmarsat's role in GMDSS on Inmarsat's website: inmarsat.com.
Iridium is a recognized Global Maritime Distress and Safety System (GMDSS) service provider. GMDSS is an international system that is designed to enhance maritime safety and security by providing a means of rapidly transmitting distress alerts and other safety related communications from ships to shore and between ships at sea.
In 2018, the International Maritime Organization (IMO) approved amendments to the GMDSS regulations that allow for the use of satellite communication systems, including Iridium, to meet the requirements for distress alerting and other safety related communication functions. This means that ships equipped with an approved satellite communication system, such as an Iridium terminal, can use it to send distress alerts and other safety related messages in compliance with GMDSS regulations.
Iridium’s GMDSS service, known as the Iridium Global Maritime Distress and Safety System (GMDSS), offers global coverage and is approved by the IMO for use on ships subject to GMDSS carriage requirements. The Iridium GMDSS service provides a range of safety related commination functions, including distress alerting, ship-to-shore and ship-to-ship voice communication, and the transmission of maritime safety information.
NAVTEX is a 518 kHz medium wave system that transmits weather alerts, navigation alerts and retransmissions of emergency messages.
NAVTEX works practically as a receiver that automatically prints the messages on a piece of paper. The equipment can also be purchased as a small box that connects to a PC.
The normal range for NAVTEX is approx. 400-500 nautical miles.
The following NAVTEX stations should be able to be used near Greenland:
TRANSMISSION TIMES UTC
Bodø Radio, Svalbard
0000, 0400, 0800, 1200, 1600, 2000
0310, 0710, 1110, 1510, 1910, 2310
Kook Island, Nuuk
0340, 0740, 1140, 1540, 1940, 2340
0350, 0750, 1150, 1550, 1950, 2350
Reykjavik Radio, Saudanes
0250, 0650, 1050, 1450, 1850, 2250
Reykjavik Radio, Grindavik
0350, 0750, 1150, 1550, 1950, 2350
0200, 0600, 1000, 1400, 1800, 2200
0120, 0520, 0920, 1320, 1720, 2120
The operating authority for the Greenlandic broadcasts at stations M, I, X, R and W is JRCC NUUK.
For GMDSS, requirements for a number of different emergency radio transmitters depend on the sea area the ship is sailing on and the ship's size, species and manning.
In A3 sea areas, so-called Inmarsat EPIRBs are used, which are capable of automatically transmitting the ship's identity and position. Inmarsat EPIRBs are in the new versions made with built-in GPS receiver.
In all sea areas, so-called COSPAS / SARSAT EPIRBs can be used, which are based on a Russian / American collaboration on satellites that orbit the earth polarly.
The COSPAS / SARSAT EPIRBs use the frequency 406MHz.
On 406MHz, the position indications of the EPIRBs are accurate to within 5 km.
In addition, the 406MHz EPIRBs also pass on the ship's identity to the rescue authorities.
In all sea areas you can also use a so-called SART. A SART is an emergency radio transmitter that, when activated, can respond to ships' 3 centimeters of radar. Newer SART are built in with an AIS transmitter.