Marine Glossary

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GMDSS

Abbreviation for Global Marine Distress and Safety System. A service coordinated by the International Maritime Organization to provide worldwide distribution of marine safety information to vessels underway. It began in 1992 and is expected to be fully implemented in 1999. Information is distributed through NAVTEX or by SafetyNET communications.

Within the GMDSS, the oceans are divided into four areas for the purposes of establishing the requirements of communications equipment needed to receive the information. Area A1 is within range of VHF coast stations (about 20 miles from the shore). Area A2 is beyond A1, but within range of MF (middle frequency) stations, which is up to about 100 miles from shore. Area A3 is beyond A1 and A2, but within coverage of INMARSAT, which is essentially worldwide except polar regions at latitudes higher than about 75°. Area A4 is polar regions not covered in A3.

Regulations and operations of GMDSS are contained in various ITU and IMO publications. Pertinent sections are presented in Chapter 4 of Radio Navigational Aids.

An extended discussion of the GMDSS program is presented in the Source Book, Page GMDSS. Schedules and information are also available on the internet. See Page internet of the Source Book.