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WHY GMDSS?

The Global Maritime Distress and Safety System (GMDSS) was introduced in 1999 to respond to shortcomings of the existing marine distress systems and, with the establishment of a coordinated search and rescue (SAR) infrastructure, improve safety of life at sea.

Prior to its introduction, marine radio equipment fitted to ocean going vessels was required to provide operation over a minimum specified range of 150 nautical miles. This was based on the assumption that ships usually travelled well-used routes and that there were sufficient ships at sea and shore stations dispersed about the world to receive distress calls. However, if a ship was outside of the normal shipping lanes or was rapidly overwhelmed by the forces of nature, her distress alert may go unheard. As a result, many ships have sunk without any distress signal being heard or even sent.

GMDSS IN USE

The GMDSS is specifically designed to automate a ship's radio distress alerting function, and, as a consequence, removes the requirement for manual (i.e. human) watch-keeping on distress channels.

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

The system also provides for urgency and safety messages and also for the broadcast of Maritime Safety Information (MSI) such as weather reports, navigation warnings and SAR messages.

The GMDSS applies to vessels subject to the International Convention for the Safety of Life at Sea (SOLAS Convention), that is:

“Commercial passenger ships engaged on international voyages and cargo ships of 300 Gross Registered Tons (GRT) and above, engaged on international voyages.”

Radio equipment requirements for ships and pleasure craft engaged on domestic voyages are determined by the vessel's Flag State (i.e. the country of registry of the vessel).

One of the principal advantages of the GMDSS is distress alerts may be sent and received over short and/or long distances; every ship is able to communicate irrespective of the area through which it sails because the radio communications equipment fitted to a GMDSS ship is determined by the ship's area of operation, rather than by its size.

GMDSS EQUIPMENT

The SOLAS GMDSS regulations are structured such that all GMDSS ships are required to carry a minimum set of equipment, with more equipment being required the further the ship travels from land.

The GMDSS utilises both satellite and terrestrial radio systems but the limitations regarding range and services provided mean equipment requirements vary according to the area the ship is trading to or through. It is possible that a small 300 ton cargo vessel may carry the same amount of communications equipment as a 300,000 ton oil tanker, if they are both operating in the same area - a marked change from the pre-GMDSS systems.

The World's oceans are divided into four Sea Areas to determine the required equipment:

	Location	Area	Service
Sea Area 1	Most European, some US and some SE Asian coastal waters	Lies within range of shore-based Very High Frequency (VHF) Coast Radio Stations (20-30 nautical miles)	Short-range services: VHF radio for voice and automated distress alerting via Digital Selective Calling (DSC)
Sea Area 2		Lies within range of shore based Medium Frequency (MF) Coast Radio Stations (excluding A1 areas) (approximately 100 - 150 nautical miles)	Medium-range services: Medium Frequency (MF) radio for voice and DSC alerting
Sea Area 3	Australia, New Zealand and the Pacific	Lies within the coverage area of Inmarsat communications satellites (Lat 70oN - Lat 70oS, excl. A1/A2 sea areas)	Long range services: High Frequency (HF 3 to 30MHz) voice; VHF DSC used for ship-to-ship alerting*
Sea Area 4	Polar regions	Comprises remaining sea areas outside areas A1, A2 and A3;	Long range alerting: High Frequency (HF 3 to 30MHz)

In many parts of the world, A3 areas extend right up to the coastline.

GMDSS Sea Areas

Note that the requirements are cumulative in nature - i.e. an A3 vessel is also equipped, by definition, with equipment for A1 and A2 Sea Areas, e.g.

• In areas where Sea Area A1 services are provided, coastal vessels are only required to fit VHF equipment (provided they remain within the declared Sea Area);
• Vessels that trade further from land are required to carry MF equipment, in addition to VHF;
• Ocean going vessels fit VHF, MF, HF and Inmarsat satellite equipment.

* In Sea Area A3, VHF DSC is used for ship-to-ship alerting. Therefore, the Australian Government is not required to provide VHF DSC shore infrastructure. However, many Australian volunteer marine rescue organisations are starting to equip their base stations with GMDSS VHF DSC equipment.