Global Maritime Distress and Safety System

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Global Maritime Distress and Safety System   (GMDSS) 


  • The basic 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 assist in a co‑ordinated search and rescue operation with the minimum of delay. The system also provides for urgency and safety communications and the dissemination of maritime safety information, including navigational and meteorological warnings.  This means that every ship will be able, irrespective of the area in which it operates, to perform those communication functions considered essential for the safety of the ship itself and of other ships operating in the same area. Although satellites play an important part in the GMDSS, terrestrial radio is still important.  The GMDSS combines various subsystems ‑ which all have different limitations with respect to coverage ‑ into one overall system, and the oceans are divided into four sea areas:   

      GMDSS Sailing Areas    

  • Area A1   Within range of VHF coast stations (about 20‑30 nautical miles)
  • Area A2  Beyond area Al, but within range of MF coastal stations (about 100-l50 nautical miles)  
  • Area A3   Beyond the first two areas, but within coverage of geostationary maritime communication satellites (in practice this means Inmarsat).  This covers the area between roughly 70 Deg N and 70 Deg S.
  • Area A4   The remaining sea areas.  The most important of these is the sea around the North Pole (the area around the South Pole is mostly land).  Geostationary satellites, which are positioned above the equator, cannot reach this far.

  The Equipment requirements

  • Equipment requirements vary according to the area (or areas) in which the ship operates.  Coastal vessels, for example, only have to carry minimal equipment if they do not operate beyond the range of shore‑based VHF radio stations.  Ships which do go further from land have to carry MF equipment as well as VHF.  Ships which operate beyond MF range have to carry HF or Inmarsat equipment in addition to VHF and MF.  Ships which operate in area A4 have to carry HF, MF and VHF equipment. In addition to radio equipment, the GMDSS introduced requirements for other equipment designed to improve the chances of survival, including float-free emergency position‑indicating radio beacons (EPIRBs) and radar transponders for location of the ship or survival craft in distress.