GMDSS – Global Maritime Distress Safety System

In the 18th century, Morse code served as the primary method for ships to send distress signals during emergencies to coastal authorities or nearby vessels in international and coastal waters. However, the transmission of distress messages through tones or lights often lacked clarity, making it challenging to understand the nature of the onboard emergency.

To address this issue, the International Maritime Organization (IMO) implemented the Global Maritime Distress Safety System (GMDSS) under SOLAS Chapter IV. GMDSS is an internationally agreed safety procedure designed to enhance maritime communication and ensure effective response during distress situations.

The Fully Implemented GMDSS: Revolutionizing Maritime Safety

On February 1st, 1999, the GMDSS was fully implemented, establishing standardized communication protocols, procedures, and safety equipment for ships during distress situations. All passenger and cargo ships above 300 gross tonnage engaged in international voyages are required to carry GMDSS-compliant equipment.

To understand GMDSS requirements in detail, it is crucial to familiarize oneself with the SOLAS regulations governing the system. These regulations outline the specific equipment needed for different types of vessels.

GMDSS Operation: Distress Signals and Communication Channels

When a ship employs GMDSS, it employs satellite or radio communication equipment to transmit distress signals. Additionally, GMDSS serves as a medium for sending and receiving maritime safety information and facilitates general communication channels.

The GMDSS framework designates various Sea Areas, each requiring specific equipment for efficient operation. The Sea Areas and their corresponding ranges and equipment allocations are as follows:

• Area A1: 20 to 50 nautical miles – VHF DSC (Very High Frequency Digital Selective Calling)
• Area A2: 50 to 400 nautical miles – VHF and MF (Medium Frequency)
• Area A3: Between 70°N and 70°S – VHF, MF, and one INMARSAT system
• Area A4: Above 70°N or S – HF (High Frequency), MF, and VHF

Understanding Frequency Ranges and VHF Communication

VHF communication plays a vital role in maritime communication, with a frequency range allocated from 156 MHz to 174 MHz. Channel 16, set at 156.800 MHz, serves as the dedicated frequency for Distress, Urgency, and Safety communication. Channel 70, at 156.525 MHz, facilitates routine VHF DSC (Digital Selective Calling) watch.

To prevent interference on Channel 16, GUARD channels are positioned above and below it. These GUARD channel frequencies, 156.775 MHz and 156.825 MHz, ensure uninterrupted traffic for distress, safety, and urgency communication.

The VHF set operates on a 24 Volt DC power supply, using J3E transmission for radiotelephony and G2B transmission for VHF DSC.

Essential Elements of GMDSS: INMARSAT, NAVTEX, EPIRB, and More

GMDSS encompasses several key components that contribute to maritime safety and distress alerting. These elements include:

1. INMARSAT: An international satellite system featuring ship earth station terminals (such as Inmarsat C) that enable telex, telephone, and data transfer services between ships, shore, and rescue centers.
2. NAVTEX: A globally adopted automated system for distributing Maritime Safety Information (MSI), including weather forecasts and warnings, navigational warnings, search and rescue notices, and other safety-related information.
3. Emergency Position Indicating Radio Beacon (EPIRB): A secondary means of distress alerting that helps determine the position of survivors during Search and Rescue (SAR) operations.
4. Search and Rescue Locating Equipment: Primarily the Search and Rescue Radar Transponder, which aids SAR units in locating distress positions by responding to interrogations.
5. Digital Selective Calling (DSC): A calling service enabling safety and distress information exchange between ships and shore or ship-to-ship communication, mainly on high or medium frequency and VHF maritime radio.

Required Documentation for GMDSS Compliance

Ships operating under GMDSS regulations must carry essential documents on board, including:

• Ship’s Radio License
• Radio Operator Certificates
• Safety Radio Certificate
• GMDSS Radio Log Book
• ITU List of Cell Signs and Numerical Identities of Stations used by Maritime Mobile and Maritime Mobile Satellite Services
• ITU List of Coast Stations
• ITU List of Ship Stations
• ITU List of Radio determination and Special Service Stations
• Antenna Rigging Plan
• Valid Shore Based Maintenance Certificate

GMDSS Training: The Key to Competence

Proficiency in handling GMDSS equipment requires certified training and licensing from the Telecommunication department. The General Operators Certificate (GOC) is a mandatory requirement for officers responsible for GMDSS equipment onboard ships.

Obtaining the GOC entails attending a compulsory short course and passing a written and oral examination. The 12-day training program is essential for cadets seeking to become licensed Radio Operators proficient in operating all GMDSS equipment while adhering to regulations.

To enroll in the GMDSS course, individuals should contact an approved institute well in advance. Eligibility and admission criteria vary by country, so prospective candidates should consult the respective institute websites and their country’s Ministry of Shipping (or relevant authority) for detailed information.

The comprehensive GMDSS training covers various aspects, including Radio Log maintenance, INMARSAT message transmission, and other communication procedures essential for onboard operations. The written exam tests theoretical knowledge, while the oral examination evaluates practical skills, ensuring candidates have a well-rounded understanding of GMDSS.

Recommended Resources for GMDSS: Books and Publications

To enhance knowledge and proficiency in GMDSS, it is recommended to consult the following publications:

1. GMDSS – A Guide for the Global Maritime Distress Safety System
2. GMDSS – A User’s Handbook
3. Admiralty List of Radio Signals (ALRS) Volume 5: GMDSS (NP285)

ALRS Volume 5 provides extensive theoretical and practical information, covering distress communication, DSC equipment operation procedures, search and rescue transponders, ITU Radio Regulations extracts, VHF DSC Coast Stations lists for different sea areas, and more. Weekly Notices to Mariners (TNM) include corrections for ALRS Volume 5 in Section 6.

The Portable Marine Radio: A Vital GMDSS Element

The portable marine radio, also known as the survival craft transceiver, plays a crucial role in GMDSS. It is located on the bridge and serves as a communication tool during survival craft boarding or general onboard communication.

In emergencies, the portable marine radio enables on-scene coordination between survival craft and search and rescue units. IMO regulations dictate specific requirements for survival craft transceivers, including ease of operation by unskilled personnel, transmission and reception frequencies (156.8 MHz – Channel 16 and 156.3 MHz – Channel 6), durability, waterproofing, power capacity, and antenna specifications.

Broadening Knowledge and Expertise in GMDSS

Given GMDSS’s mandatory nature onboard ships and its critical role in emergency situations, it is crucial for officers to possess comprehensive knowledge of every aspect of the system. Extensive reading of publications, manuals, and other available resources is highly recommended to enhance proficiency in handling GMDSS equipment and further understand its setup.

By investing time and effort into learning about GMDSS, officers can ensure the safety of maritime operations and effectively respond to distress situations, contributing to the overall well-being of crew members and the security of vessels at sea.