GMDSS Basics: Distress Alerts, EPIRBs, and Maritime Safety Information

The Global Maritime Distress and Safety System (GMDSS) connects ships with shore services and other vessels using several communication technologies. Its purpose is to improve the chance that a distress alert reaches people able to coordinate or provide assistance.

This overview explains the system. It does not teach equipment operation; only qualified training and the vessel’s approved procedures should do that.

A network, not one device

Depending on the vessel and sea area, the GMDSS arrangement may include terrestrial and satellite radio services, Digital Selective Calling (DSC), emergency position-indicating radio beacons (EPIRBs), search-and-rescue locating equipment and receivers for maritime safety information.

Each component has a defined purpose. Equipment carriage, maintenance and qualified operation depend on the vessel’s requirements.

Distress, urgency and safety

• Distress concerns grave and imminent danger requiring immediate assistance.
• Urgency concerns an urgent message about the safety of a ship, aircraft, person or vehicle without necessarily meeting the distress threshold.
• Safety communications include important navigational or meteorological warnings.

Use the terminology, priority and procedure taught in approved training. An incorrect transmission can delay response or create confusion.

EPIRBs in context

An EPIRB can transmit identifying and position-related information through a satellite-supported alerting chain. Registration details, installation, testing and maintenance are critical. Crew should know the vessel-specific location and assigned emergency duties, but should not improvise activation or testing from a web article.

Preventing and responding to false alerts

False alerts burden rescue services and may divert resources. Follow authorised test procedures, protect equipment from accidental activation and report a false alert immediately using the prescribed cancellation process. Never ignore an accidental activation in the hope that it will disappear.

Maritime safety information

GMDSS also distributes navigational warnings, meteorological warnings and forecasts, and other urgent safety information. Watchkeepers must understand which equipment and procedures deliver this information on their vessel and ensure it is considered in operations.

Familiarisation checklist

• Know who is qualified and responsible for radio duties.
• Locate relevant equipment and backup power arrangements.
• Understand where operating instructions and logs are kept.
• Know your muster-list communication role.
• Report defects or expired service items.
• Participate in authorised drills without transmitting a real alert.

Authoritative references

• IMO — Radiocommunications and Search and Rescue
• IMO — Circulars related to the GMDSS
• IMO — SOLAS Convention