What is GMDSS?

GMDSS- The Global Maritime Distress & Safety System

The Global Maritime Distress and Safety System (GMDSS) was created by the International Maritime Organization (IMO);

“The basic concept of (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 that they can assist in a co-ordinated SAR operation with the minimum delay.

The system also provides for agency and safety communications and the promulgation of Maritime Safety Information (MSI) – navigational and meteorological warnings and forecasts and other urgent safety information to ships.

Vessel over 300 GT are “Compulsory Fit,” i.e. they are required under SOLAS to carry GMDSS equipment. Vessels under 300 tonnes are Voluntary Fit. Voluntary fit vessels are often still required under other domestic legislation to carry certain GMDSS equipment (such as a VHF radio).

What is the Benefit of GMDSS?

All Distress and Safety communication are automated and watch keeping on traditional voice and morse code frequencies has been resigned to the history books. It is no longer a requirement for ships to maintain a listing watch 24/7. The days of round the clock radio operators (sparks) on board ships are over, instead all watch officers are now GMDSS radio trained; we offer those courses here.

At the press of a button, a ship can send its identity, position and nature of distress by either satellite or terrestrial communication. Under GMDSS, Search and Rescue is no longer co ordinated by the first ship on scenes. A Rescue Co-ordination Centre (RCC) coordinates search and rescue and alerts other vessels in the area to go to the aid of the casualty.

What are the Components of GMDSS?


  • Digital Selective Calling (DSC)
  • EPIRBs
  • SARTs
  • VHF, MF and HF Communication.

What are the GMDSS Sea Areas?

There are 4 GMDSS areas, A1, A2, A3, A4.

Sea Area Summary Equipment carried on GMDSS compliant vessels
Sea Area A1 Within VHF range of a coast station (typically about 35 NM)
  • Handhel VHF
  • SART
  • Navtex
Sea Area a2 Within MF range of a share station (typically 150-180 miles) and excludes A1
  • As above plus
  • MF/DSC
Sea Area A3 Within coverage of INMARSAT geostationary satellites (between Latitides 70-degress North and 70 degrees South_ and excludes A1and A2
  • As above plus
  • HF/DSC
  • Inmarsat C and/or Fleet Broadband
Sea Area A4 The Polar regions (North of 70 degrees North and South of 70 Degrees South,
  • As above plus
  • MF/HF Telex


When did GMDSS come into force?

Full operation of the Global Maritime Distress and Safety System came into force on the 1st February 1999. Under IMO legislation, all passenger vessels had to be fitted with the necessary equipment by 1995 and all vessels over 300grt to be GMDSS equipped by the 1st February deadline. It is fair to say they not every national administration had put the necessary shore based infrastructure in place by the deadline, however by the mid naughties the “slower” nations had caught up.

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