Global Maritime Distress and Safety Communication System GMDSS, Global Maritime Distress and Safety System.

GMDSS was developed by the International Maritime Organization (IMO) with the support of the International Telecommunication Union (ITU) to increase the reliability of distress communications at sea with modern radio equipment. 

Global Maritime Distress and Safety Communication System GMDSS, Global Maritime Distress and Safety System.

The key features of GMDSS compared to the previous Search And Rescue, SAR maritime rescue system:

The rescue operations center is shifting from nearby vessels, limited by the range of medium-wave communication of about 150-200 nautical miles, to the coastal marine rescue coordination centers (MRCC). The introduction of satellite communications equipment dramatically increases the likelihood of successful sending and receiving distress signals. Especially for ships remote from busy trade routes.

Automation of the transmission and reception of distress signals, which increases the reliability of their sending and avoids the constant watch of the radio operator on distress channels (Distress Channels, 2182 kHz at medium waves, 16 channel in the VHF band).

The essence of the GMDSS system is that coastal rescue services, as well as ships in the immediate vicinity of a ship in distress, wherever it is, automatically and very quickly receive the necessary information. This allows for effective rescue operations without delay..

In addition to distress alerts, GMDSS is also used to send urgent messages (Urgency) about the need for repairs or medical assistance, safety warnings, warnings about navigational hazards and the approach of storms, and weather forecasts.

Starting February 1, 1999, all cargo ships with a gross tonnage of more than 300 tons or passenger ships carrying more than 12 passengers engaged in international transportation must fully comply with the requirements of the GMDSS.

Although these requirements do not apply to yachts and small boats, consider whether it will be superfluous at sea to know how you can be saved in the event of any troubles and what equipment exists for this.?

Functions and radio equipment GMDSS.

In developing the GMDSS global distress alert system, IMO first identified the functions that ship radio equipment should perform:

1. A distress signal from ship to shore. Moreover, it should be possible to transmit such a signal at least in two independent ways, through different systems in different ranges of radio waves.
2. Receiving distress signals from shore to board a ship.
3. Receive a distress signal from another vessel.

4. Receiving and sending messages by the head of the rescue operation directly at the operation site from the coastal coordination center in order to interact with all ships and aircraft involved in the search and rescue.
5. Receiving and sending messages from the head of the operation directly at the place of the rescue operation by the vessels directly involved in the operation.
6. Signaling of the position of other vessels, mainly using radar.

7. Sending and receiving messages on navigation safety (navigational hazards and weather forecasts).
8. Transmission and reception of general messages from coast stations and public information networks.
9. Transmission and reception of bridge-to-bridge messages, used mainly when entering a port or during piloting.

Radio waves of different frequencies propagate in different ways, and the range of an instrument depends on the propagation method. Therefore, another significant difference between the new system and the previous one is the equipment of ships with radio equipment, not depending on the size of the vessel, but depending on its distance from coast stations or, in IMO terms, from the sea navigation area.

GMDSS Marine Sailing Areas.

A careful analysis of the available technical systems and communication devices led the creators of GMDSS to a natural definition of navigation areas:

GMDSS Area A1 GMDSS A1 marine navigation area, covering the coverage area of ​​coastal VHF radio stations. About 20 30 miles from the station.
GMDSS Area A2 navigation area A2, covering the coverage area of ​​coastal medium-wave stations and not including area A1, 100 150 miles from the station.
GMDSS Area AZ AZ navigation area, covering the Inmarsat satellite coverage area and not including A1 and A2. Earth’s surface, with the exception of subpolar regions, starting at 70 degrees north and south.
GMDSS Area A4 area of ​​navigation A4 all the rest of the earth’s surface, not covered by areas A1, A2 and AZ. These are the circumpolar regions where there are no VHF or mid-wave coastal stations.

Great Britain and northwestern Europe.

Global Maritime Distress and Safety Communication System GMDSS, Global Maritime Distress and Safety System.

IMO member countries that have adopted the SOLAS / GMDSS convention are required not only to equip their ships with radio equipment appropriate to the navigation area, but also, with possible cooperation with neighboring countries, to provide coastal infrastructure.

It is important to understand that the navigation area does not start from the coastline, but from the corresponding coastal radio station. So, for example, in Australia there are no A1 and A2 districts; the entire continent is a AZ region. There are simply not enough VHF and CB radio stations on the coast.

Based on the book Yacht Captain. Training manual for owners of sailing and motor yachts.
Vatrunin B.

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