Scott Simmons explain how the new Global Maritime Distress and Safety System works.

When the Titanic struck an iceberg off Newfoundland on the night of April 14, 1912 and sank with the loss of 1,500 lives it prompted international agreements to improve safety procedures at sea.

Considered by most marine historians to be the worst casualty ever, the loss of the Titanic was even more ironic because she boasted the latest technological developments available, including radio, using Morse code which had been developed in 1899. Thirteen years later, Jack Phillips, Chief Radio Officer on the Titanic, keyed the historic distress message from his cramped radio room, which was received by a nearby ship, Californian (which failed to respond) and other vessels, thus setting the trend for marine distress communications through two world wars, and up to the present. Phillips remained at his post so long that he lost all chance of saving himself, and went down with the ship.

Morse code is still used for distress communications with ships at sea - three dots, three dashes, then three dots remains the universally-recognised `SOS' call - and was integral to the success of a distress case handled by Bermuda Harbour Radio less than a year ago. The Chilean-registered vessel Vienna was 160 miles northeast of Bermuda when Harbour Radio intercepted a distress call and issued a distress broadcast in Morse code.

But Morse code, where marine distress communications are concerned, is on the way out, and by the end of this century will truly be in the history books.

The International Maritime Organisation (IMO) has developed the Global Maritime Distress and Safety System (GMDSS), described as "the single most fundamental change in marine communications since the use of wireless telegraphy, and Morse code.'' Implementation commenced in 1992, and will continue through to 1999 when all vessels above 300 gross tons must comply.

Prior to GMDSS all ships of 1600 gross tons and above were required to carry a qualified Radio Officer, who was responsible for all communications and particularly distress working. Under GMDSS this is no longer a requirement, and with the correct equipment onboard, a distress message can be sent via satellite simply by pressing a button on the bridge. Satellites are a vital component of the new system. Inmarsat (International Maritime Satellite Organisation) operates a system of satellites which currently provide a range of high quality mobile telecommunications services.

Any vessel fitted to comply with GMDSS requirements can send a distress message via Inmarsat or Digital Selective Calling (DSC). DSC utilises the present short, medium and long range marine calling bands, and is used primarily for distress alerting and acknowledgment. With DSC, a message is transmitted on the appropriate distress channel which contains the identification of the transmitting station and it's position. On the receiving end, a dedicated receiver monitors the DSC distress channels, and automatically picks up any distress calls within range. Once the initial distress call has been received by a shore station such as Harbour Radio, or another ship, communications can be conducted using Inmarsat, or conventional maritime radio channels. Despite the fact that GMDSS will account for practically all of the world's merchant and passenger fleet, there are concerns that smaller vessels on ocean passages will be vulnerable, as they are not required to be similarly equipped.

GMDSS has far reaching repercussions for ALL mariners, including local smallcraft owners. Local mariners would particularly benefit from the use of EPIRBS (Emergency Position Indicating Radio Beacons), and NAVTEX (which automatically receives and prints maritime data).

The EPIRB is perhaps the most valuable single piece of safety equipment developed in the last 20 years. Recommended to anyone travellingoffshore, it has been directly responsible for saving the lives of many hundreds of mariners around the world. The EPIRB is essentially a small radio transmitter, which when activated, not only indicates distress, but also enables the position of the beacon to be determined. The unit can be manually activated by the user, or with some models, automatically, as it floats clear of the sinking vessel.

Most EPIRBs utilise the aviation distress frequency of 121.5Mhz and generate a distinctive signal which was originally intended to be received by aircraft flying overhead, which would then relay the position of the signal to the appropriate authorities for action. It was quickly realised that outside of the major air traffic routes, aircraft activity was so infrequent that vast areas of the world were left uncovered, and that another method of detection would be needed if the system was to be truly successful. In a collaborative effort between Canada and France, Search and Rescue Satellite Aided Tracking (SARSAT) equipment was designed and placed aboard low polar-orbiting satellites launched by the USSR in 1982, and the United States in 1983 which led to the international satellite network known as the COSPAS ARSAT system.

This system today is funded by numerous countries around the world.

Vessels of any size can freely access this international alert network simply by activating their EPIRB in an emergency when all conventional means of communication have failed. Once activated, the beacon will either be detected by overhead aircraft, or the various search and rescue satellites that orbit the earth approximately every 105 minutes. The 121.5 Mhz EPIRB system has been found to provide a position accuracy to within 10 to 20 miles of the distress vessel's actual position, and this information is relayed to the Rescue Co-ordination Centre who can then devise a suitable rescue plan, using whatever resources are available.

One problem with EPIRBs is that of false or accidental activation, and "distress'' signals have been tracked down to unusual locations, such as the sorting room of a London Post Office or, in one case, to a bedroom in northern England. The owner had brought his EPIRB home and had inadvertently hit the transmit button! Within the last five years an improved EPIRB, designed specifically for interaction with the COSPAS ARSAT satellites has been introduced to the market. This model utilises a more suitable frequency of 406Mhz and transmits a digitally encoded signal which allows the vessel to actually be identified, it's nationality determined, and other information obtained from an international database network on which the vessel is entered by prior registration. In fact, on some models, the type of distress can be indicated, while the improved position accuracy of the 406Mhz EPIRB will enable determination of a distress position to within 1 to 5 miles.

NAVTEX is a means whereby any vessel with the appropriate NAVTEX receiver fitted, can receive a printed report of all maritime broadcasts transmitted by shore stations. NAVTEX is a medium range service (up to approximately 400 miles), and NAVTEX stations are located strategically around the globe, focussing primarily on local maritime information. A station such as Harbour Radio transmits all navigational and meteorological data at scheduled times during a 24 hour cycle. All messages are coded for weather, navigational warnings and safety messages, with priority given to distress or urgency traffic. If a distress message is transmitted by NAVTEX, the receiver onboard is programmed to receive this message before any other. Instead of the person at sea having to monitor a voice or Morse transmission, they are able to receive a printed copy, rather like having a fax on board. Once a particular message is printed out aboard the vessel, it will not be printed out again by the NAVTEX receiver for 72 hours. This reduces received traffic considerably, but ensures that all new messages will be received. Distress messages are received regardless.

NAVTEX transmissions use a communications technique known as Forward Error Correction (FEC), sending text that has been changed to Baudot format. Each letter of the alphabet, or number is represented by a five unit binary code, instantly recognisable as the old "ticker tape'' seen in scores of movies when some important news item was being eagerlyawaited. Via a type of modem, a seven bit code is outputted for transmission to ships via marine radio on 518 Khz using Frequency Shift Keying (FSK). The multi-element coding system was perfected by Emile Baudot in 1874, used extensively for data communications well into the 20th century, and now a significant element of GMDSS. A circle of sorts was completed when a NAVTEX broadcast from Harbour Radio was recently received by the Woods Hole R Atlantis II at a range of 250 nautical miles.

Atlantis II, among other things, is famous for helping to discover the sunken hull of the Titanic in 1985.

Had GMDSS and NAVTEX been available in 1912, and the ill-fated Titanic fitted with just a 406Mhz EPIRB, the course of marine history may well have been different.

Footnote: Many aspects of GMDSS do not apply to local smallcraft and, despite space-age technology using orbiting satellites, common sense on the water goes a long way.

Local mariners are urged to file a float plan before taking to the water. A float plan means advising Harbour Radio, Marine Police or any responsible person, where that particular boat intends going, and for how long. Other information, such as number of persons aboard, and safety equipment should be included where possible. Smallcraft owners must ensure they carry basic safety items such as lifejackets, anchors and flares. Finally, pay close attention to marine weather forecasts. Continuous marine weather forecasts are transmitted by VHF on the Marine Weather Channel CH 02, and Bermuda Harbour Radio broadcasts weather and safety messages at scheduled times.

Joe Pagnam and Scott Simmons are radio officers with Harbour Radio. Joe Pagnam also writes the weekly On the Run column in the Mid-Ocean News and wrote about International Race Weekend in February's RG Magazine.

GMDSS enables ships in distress to send a message in vaious ways and be virtually certain it will be heard and acted upon. Messages are picked up by ships and shore stations in range, if sent on MF and VHF, or by shore stations if transmitted bia HF, INMARSAT or COSPAS-SARSAT system.

RG MAGAZINE MAY 1993