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Global maritime distress safety system

The global maritime distress safety system (GMDSS) connects you with satellite and radio communications when you're out at sea.

The GMDSS allows you to contact stations and vessels with satellite and radio communications if you are in distress at sea. 

Radios have been used to save lives at sea since 1899. Lives were saved when another vessel or shore station was within range to receive the call and respond. These methods have included the manual sending of morse code and radiotelephone messages.

The GDMSS was introduced in 1992. The system transformed the way a distress alert can be transmitted and received in the maritime environment. The GDMSS has become a key element of maritime search and rescue (SAR) systems internationally.

The GMDSS uses satellites and digital selective calling (DSC) on the MF, HF and VHF bands. This enables a distress alert to be transmitted and received automatically over both short and long distances.

The concept of GMDSS is that SAR authorities ashore, as well as ships within the immediate vicinity of a vessel in distress, will be rapidly alerted to a distress incident and provide assistance as required under the International Convention for the Safety of Life at Sea (SOLAS Convention).

SOLAS convention

The SOLAS convention is a set of international regulations and standards governing all operational aspects of merchant ships. The convention has been endorsed by all major maritime nations which operate through the International Maritime Organisation (IMO).

All ships over 300 gross tonnage on international voyages are subject to the SOLAS convention and must comply with the carriage requirements of the GMDSS. The equipment carriage requirements will be determined by the area in which a vessel is operating within otherwise known as sea areas.

Australia’s sea area

Australia holds sea area A3 which is within the coverage of an INMARSAT geostationary satellite, providing continuous alerting.

As part of its obligation, Australia provides a satellite and HF radio-communications service.

While 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 with its own stations.

Read more on the INMARSAT satellite coverage.

Our role in the GDMSS

We provide for Australia’s GDMSS requirements through:

  • digital selective calling (DSC) which is used for ship to shore distress alerting and shore to ship distress relay via the HF DSC network
  • continuous automatic monitoring of the GMDSS DSC distress and safety channels:
    • 4207.5 kilohertz
    • 6312 kilohertz
    • 8414.5 kilohertz
    • 12577 kilohertz
    • 16804.5 kilohertz
  • capability to transmit and receive on any frequency between 2 – 27 megahertz using:
    • radio-telephony (single side band, suppressed carrier)
    • GMDSS narrow band direct printing (NBDP) telegraphy
    • GMDSS DSC, including the automatic response to DSC test calls
    • limited capability to connect MF/HF radiotelephone services to the public switched telephone network (PSTN) for services such as medical advice to ship masters.

High frequency distress and safety communications (HF DSC) network

Strategically positioned in Wiluna, Western Australia and Charleville, Queensland all GMDSS HF radio services are provided by the AMSA HF DSC network and controlled by the Network control centre within the Joint rescue coordination centre in Canberra.

The network monitors the DSC distress frequencies and conducts follow on communications via radiotelephony or NBDP. The network has the capability to make broadcasts for search and rescue purposes and these will normally be preceded by a DSC announcement message.

Any vessel that fits the appropriate GMDSS compatible equipment has access to use the AMSA HF DSC network, however:

  • Vessels fitted with sailor equipment may need to program in a position for the stations (latitude and longitude).
  • Vessels off the west coast of Australia might call Wiluna at 26 20.45' south 120 33.40' east. Vessels off the east coast might call Charleville at 26 19.83 south 146 15.85' east.

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