Global Maritime Distress and Safety System (GMDSS)

The Global Maritime Distress and Safety System is a worldwide system to support maritime search and rescue operations. The primary goal of GMDSS is to alert search and rescue (SAR) authorities ashore and ships in the vicinity of the ship in distress so they can assist in a co-ordinated search and rescue operation with minimum delay.

The Global Maritime Distress and Safety System uses both satellite and terrestrial radio systems because each system has its own individual limitations with respect to geographical coverage and services it can provide. The system also provides some limited ship to ship communications capabilities. In addition to communication equipment, GMDSS requires equipment to improve the chances of survival in distress situations. This includes a position indicating radio beacon (EPIRB) and a radar transponder (SART) to localize a ship in distress or survival craft. Last but not least, GMDSS includes a system to provide maritime safety information (MSI), including navigational and meteorological warnings.

The GMDSS includes the following systems:

• Communications equipment
• VHF/MF/HF maritime radio,
  capable of Digital Selective Calling(DSC);
• Inmarsat satellite communications.

• Positioning and localization systems
• Emergency position-indicating radio beacons (EPIRB);
• Search and Rescue radar transponder (SART).

• Maritime Safety Information
• NAVTEX;
• SafetyNET.

The requirements for the communication and MSI equiment depends on the area in which the ship operate. There are 4 different areas defined:

Area A1
within range of VHF coast stations
(up to 20 - 30 miles from the coast),
Area A2
beyond area A1 but within range of MF coastal stations
(up to about 100 miles from the coast).
Area A3
beyond area A1 and A2, but within coverage of an Inmarsat satellite. They covers the globe except the area near the north and south pole
(roughly the area between 70° N and 70° S).
Area A4
the remaining sea area. This area is covered by HF coastal stations.

An EPIRB and SART are always required.

Every ship subject to the communications act or the safety of life at sea (SOLAS) convention must comply with GMDSS. These vessels include:

• All passenger ships regardless of size
• Cargo ships of 300 gross tons and upward