GMDSS Concept | GMDSS services provided by AMSA | AMSA HF DSC Network | Maritime radio services for small craft
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The Global Maritime Distress and Safety System (GMDSS) concept

The basic concept of the GMDSS is that search and rescue authorities ashore, as well as shipping in the immediate vicinity of a ship in distress, will be rapidly alerted to a distress incident so they can assist in a coordinated search and rescue operation with the minimum of delay.

A key concept of the GMDSS is that of Sea Areas. The oceans of the world have been divided into operational Sea Areas, defined according to the radio facilities provided on shore for distress alerting. This approach recognises the capabilities and limitations of the various communications techniques employed in the GMDSS.

The maritime administration of each contracting government to the SOLAS 1974 convention will define the sea areas(s) for its country, using criteria given in IMO Resolution A.801(19) [PDF Icon PDF: 45KB]. The concept of sea areas is fundamental, since GMDSS equipment carriage requirements are based not on the size of a ship, but on the sea area(s) in which it operates.

The SOLAS Convention Chapter IV, Regulation 5, sets out the services which contracting Governments undertake to make available, as they deem practical and necessary, either individually or in cooperation with others. Governments are to provide appropriate shore-based facilities for Inmarsat satellite and terrestrial radiocommunication services having due regard for the recommendations of the IMO.

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Australias Sea Area A3

Australia has declared Sea Area A3 which is defined at SOLAS IV Regulation 2.1.14 as:

an area, excluding sea areas A1 and A2, within the coverage of an INMARSAT geostationary satellite in which continuous alerting is available. Resolution A.801(19) [PDF Icon PDF: 45KB] at Annex 3, paragraph 4 gives guidance that this area is where: the elevation angle of an Inmarsat satellite is 5° or more. This roughly equates to latitudes 70° north and south.

chart of INMARSAT's satellites coverage

In accordance with Annex 1 to Resolution A.801(19) [PDF Icon PDF: 45KB], for sea area A3, Governments are invited to provide radiocommunications for the following purposes:

  • Reception of ship-to-shore distress alerting;
  • Transmission of shore-to-ship distress alerting;
  • Transmission and reception of search and rescue coordinating communications;
  • Transmission and reception of navigational and meteorological warnings and urgent information; and
  • Transmission and reception of general radiocommunications.

The shore-based satellite and radio equipment facilities include both Inmarsat and HF radio facilities. The frequencies and watch requirements are those needed to service the ship-fits specified for the A3 area at SOLAS Chapter IV Regulation 10.

In summary, Australia accepts its obligation to provide satellite and HF radiocommunications services to satisfy the two equipment fit options provided for ships which transit the A3 sea area as defined in SOLAS Chapter IV. The Inmarsat Pacific Ocean Region (POR) and Indian Ocean Region (IOR) provide complete coverage of Australias maritime area of interest (SRR and NAVAREA X). Resolution A.801(19) [PDF Icon PDF: 45KB] Annex 2 Appendix 1 provides the principles for establishing HF DSC coast stations for sea area A3.

Whilst there may be other Governments establishing HF facilities in the Indian and Pacific Ocean areas, Australia aims to cover the Australian Search and Rescue Region (SRR) to a high level of probability with its own stations.

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