Australian Maritime Safety Authority

About the GMDSS

Connecting those out at sea

The Global Maritime Distress Safety System (GMDSS) allows people in distress to contact stations and vessels with both satellite and radio communications.

What is the Global Maritime Distress and Safety System (GMDSS)?

Radios have been used to save lives at sea since 1899 with the hope that another vessel or shore station was within range to receive the call and respond.

Historical methods have included:

  • manually sending of Morse code
  • radiotelephone

Since the introduction of the Global Maritime Distress and Safety System (GMDSS) in 1992, the way a distress alert can be transmitted and received in the maritime environment has:

  • completely transformed maritime radio-communications
  • become a key element of maritime search and rescue systems internationally.

GMDSS uses satellites and Digital Selective Calling (DSC) techniques on the MF, HF and VHF bands, enabling a distress alert to be transmitted and received automatically over both short and long distances.

The concept of GMDSS is that search and rescue authorities ashore, as well as ships within the immediate vicinity of a ship in distress, will be rapidly alerted to a distress incident and provide assistance as required under the SOLAS Convention.

What is the SOLAS Convention?

The International Convention for the Safety of Life At Sea (SOLAS) is a set of international regulations and standards governing all aspects of merchant ships operation. The convention has been ratified 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 1974 SOLAS Convention and are required 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.

What is Australia’s Sea Area?

chart of INMARSAT's satellites coverage

Australia declares Sea Area A3, which is within the coverage of an INMARSAT geostationary satellite, providing continuous alerting.

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

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) with its own stations.

What is AMSA’s role in the Global Distress Maritime Safety System (GDMSS)?

The Australian Maritime Safety Authority (AMSA) provides for Australia’s Global Maritime Distress Safety System (GDMSS) requirements via:

  • Digital Selective Calling (DSC) – 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 kHz
    • 6312 kHz
    • 8414.5 kHz
    • 12577 kHz
    • 16804.5 kHz
  • capability to transmit and receive on any frequency between 2 – 27 MHz, 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
    • a 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 and Charleville, Australia, all GMDSS HF radio services are provided by the AMSA HF DSC network and controlled by the Network Control Centre within JRCC in the Canberra AMSA office.

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.

Note: 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.

AMSA HF DSC Network

Related information

For non-emergency Australian Maritime Safety Authority contacts, please visit the contact us page.

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