Staying Safe at Sea – Introduction to GMDSS

  • Post category:Safety
  • Reading time:12 mins read

Safety has always been a core part of Marintech Marketing. We believe that a great boating adventure always starts with being safe while you are out at sea. Nothing beats being well prepared while you are in the middle of a crisis in the vast ocean.

In this article, our Marine Electronics Division will cover some basic concepts and technical aspects of Global Maritime Distress and Safety System (GMDSS) equipment in order for boaters to have a better understanding of GMDSS equipment.


Introduction to GMDSS

What exactly is GMDSS and why does the local authorities place such emphasis on it during inspections and surveys? The GMDSS is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats and aircraft.

A GMDSS system consist of various components. The system is intended to perform the following functions:

  • Alerting (including position of vessel in distress)
  • Search and rescue coordination
  • Locating (homing)
  • Maritime safety information broadcasts
  • General communications
  • Bridge-to-bridge communications

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

However ,despite this regulation, we still advise all recreational vessels (especially those who cross into deeper waters) to equip themselves with various extra GMDSS equipment like a search and rescue transponder (SART) or a Personal Locator Beacon (PLB).

Essential Boat Safety Equipment

Safety Equipment List extracted from MPA's Singapore-Registered Pleasure Craft Guidebook

The Singapore-Registered Pleasure Craft Guidebook produced by MPA is extremely useful and handy to have around. It includes boating guidelines, navigational tips, collision prevention practices and much more. Instead of purchasing the items just for the sake of passing the boat inspection, it is important to know what you’re buying and how to use them in an emergency, especially for GMDSS equipment.

GMDSS Equipment

VHF/DSC Transceiver

The most basic GMDSS equipment that is both mandatory and key in boating communications. Do practice basic radio etiquette and be always be respectful!


Another mandatory GMDSS equipment in our local waters, an AIS is the primary method of collision avoidance for water transport. It can also be used to identify the location of a vessel in distress.


A search and rescue transponder (SART) is a self-contained, waterproof transponder intended for emergency use at sea. Working on the same frequencies as an AIS/VHF, these transponders are able to float and last minimally for 96 hours.


The radar-SART is used to locate a survival craft or distressed vessel by creating a series of dots on a rescuing ship’s radar display. However, it will only work on X-Band radars.


Having an EPIRB on an international voyage is critical where there are no nearby ships or ports to call at during an emergency. A global satellite constellation ensures world-wide signal coverage.


A Personal Locator Beacon (PLB) can be attached to a lifejacket and activated if one falls overboard and is separated from the vessel


Navtex allows a vessel to receive navigational and meteorological warnings and forecasts, as well as urgent maritime safety information (MSI) to ships.

Satellite Transceiver

Satellite services such as Iridium and Immarsat provide global maritime distress services such as search and rescue operations. 

GMDSS in Singapore's Context

In Singapore, The Maritime and Port Authority of Singapore (MPA) is responsible for co-ordinating maritime search and rescue (SAR) operations within Singapore’s maritime search and rescue region (SRR).

Operating 24 hours, the Port Operations Control Centre (POCC) operates a shore-based Global Maritime Distress and Safety System (GMDSS) facility to monitor distress alerts and calls from ships, and co-ordinate SAR operations. It also disseminates Maritime Safety Information (MSI) through the VHF, NAVTEX and SafetyNET systems.

For more accurate and up-to-date information on GMDSS in Singapore, please visit:


24-hour emergency contact

  • VHF Channel 16
  • Tel (+65) 6226 5539 or (+65) 6325 2493
  • Telex: 20021
  • Email:

Operated by the POCC, the GMDSS monitors distress alerts and calls from ships round the clock via:

  • VHF Channel 16
  • VHF DSC Channel 70
  • COSPAS-SARSAT system
  • Inmarsat services (Sentosa LES)
  • Singapore POCC’s designated MMSI number is 005630002

MSI Broadcast

Routine broadcast of navigational warnings, weather bulletin and other information related to safety of navigation is conducted via:

  • VHF Channel 9
    Timing of broadcast: Once every two hours commencing from 0100h (UTC)
    POCC transmitter identification character is “C”.
    Timing of broadcast: 0020–0030h; 0420–0430h; 0820–0830h; 1220–1230h; 1620–1630h and 2020–2030h (UTC).
    The weather bulletin is broadcast twice daily at 0020h and 1220h (UTC).
  • SafetyNET
    Broadcast is conducted on an ad hoc basis.