What is distress communication in GMDSS?

The Global Maritime Distress and Safety System (GMDSS) is a globally accepted and adopted set of rules protocols and prescriptions, which assure safety navigation and shipping. The GMDSS equipment is applied to increase safety and make it easier and faster to rescue distressed ships, boats and aircrafts. The GMDSS enables a ship in distress to send an alert using various radio systems. Thanks to this system the alerts has a very high contingency to be received by either shore rescue authorities and/or other vessels in the area.

Since the invention of radio at the end of the 19th century, ships at sea have relied on Morse code, invented by Samuel Morse and first used in 1844, for distress and safety telecommunications. But this mean appeared difficult and not reliable enough to assure the safety at sea in full volume.

So the International Maritime Organization (IMO), a United Nations agency specializing in safety of shipping and preventing ships from polluting the seas, began looking at ways of improving maritime distress and safety communications.

A new system, gone to rely on means of satellite and on-land radio services, besides, it has changed international distress notifications from ship-to-ship based to ship-to-shore (Rescue Coordination Center) based. The GMDSS assures capability of vessels of automatically distress alerting and locating for the cases where there is no time to send an SOS or MAYDAY call. And, for the first time, the system requires ships to receive broadcasts of maritime safety information that could prevent a distress, which became a primary target. In 1988, IMO amended the Safety of Life at Sea (SOLAS) Convention, requiring ships subject to it obligatory fit GMDSS equipment. Such ships were required to carry NAVTEX and satellite EPIRBs by August 1, 1993, and had to fit all other GMDSS equipment by February 1, 1999. US ships were allowed to apply GMDSS in lieu of Morse telegraphy equipment by the Telecommunications Act of 1996.

The GMDSS has introduced new technology which has completely transformed maritime radio- communications. The new system enables a distress alert to be transmitted and received automatically over long range, with a signi cantly higher reliability.

The GMDSS composes of different systems, some of which are new, but many of which have been in use long before. The system is intended to perform the following functions: alerting (including position determination of the unit in distress), search and rescue coordination, locating (homing), maritime safety information broadcasts, general communications, and bridge-to-bridge communications. Specific radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. The GMDSS also considers back-up instrumentation of distress alerting, and emergency sources of power.

Recreational vessels do not need to comply with GMDSS radio carriage requirements, but should increasingly use the VHF radios with Digital Selective Calling (DSC). Vessels under 300 Gross tonnage (GT) are not subject to GMDSS requirements.

GMDSS equipment must be simple to operate and (wherever appropriate) be designed for unattended operation.

Distress Alerts must be able to be launched from the position where the ship is usually navigated (ie; the bridge). Also EPIRBs are required to be installed close to that place, or be capable of remote activation.

A simplified version of the equipment required by SOLAS to be carried on board for each sea area is described below.

Because the different radio systems incorporated into GMDSS have individual limitations with respect to range and service provided, the equipment required to be carried by a ship is determined by the ship’s area of operation. The GMDSS has divided the world’s oceans into four distinct areas. All vessels are required to carry equipment appropriate to the sea area or areas in which they trade.