World shipping is updating its radio equipment and radio procedures to a new system called Global Maritime Distress and Safety System. Intended originally for commercial shipping, GMDSS will have a significant effect on the leisure user. Anyone looking to fit new radio equipment should be aware of the implications.

GMDSS is a maritime communication system that includes all forms of distress alerting, safety messages, commercial correspondence and ship-to-ship radio systems. Making use of the latest computer technology, most common procedures are performed automatically. Designed to work with all types of radio including VHF, MF/HF and the Inmarsat satellite communications system, GMDSS provides a common worldwide safety and communications system. Yachtsmen will be most interested in the implications for VHF users.

Yachts will not be required to change over to GMDSS but there are many reasons why you might seriously consider it. The capability to send distress messages automatically at the press of a button is a real breakthrough that allows even untrained operators to initiate an effective Mayday. Similarly, the ability to listen without having to suffer the incessant chatter so often heard on channel 16 will come as a great blessing especially to those sailing in busy south coast waters.

Commercial ships will become difficult to contact on Channel 16 once they switch entirely to GMDSS-based systems. In the long term there are proposals to dedicate Channel 16 purely to distress and safety functions; initial calls to make contact will then be conducted via a new system called Digital Selective Calling.

Digital Selective Calling

Digital Selective Calling lies at the very heart of GMDSS. Using Channel 70 (a frequency not used for voice communication) a VHF radio equipped with DSC will be able to call one or more other DSC equipped radios with a short message giving the calling station's identity, position and a limited amount of additional information in the form of a text message displayed on a screen. This additional information can be a simple request for contact on a specified voice frequency, or more significantly, a distress message.

More complex sets will offer a range of additional facilities. With the right equipment, it will, for example, be possible to put out a call to all ships within a specified range. Using the GPS position facility, the transmitting vessel is able to put out a call requesting other ships in a specified geographical area to respond. Any vessel receiving the call also knows its position and only sends a response if it is within the prescribed area. Among the most obvious uses for such a facility would be contacting other vessels in close proximity with whom there might be a collision risk.

On a more sophisticated level, DSC will allow the tracking of commercial vessels in busy Shipping Lanes. Regular interrogation of all DSC equipped ships will provide a unique identity number and information on course and speed for each ship. When combined with information form radar, the authorities will be able to use the information to precisely monitor the activities of every vessel in a controlled area.

Although it appears similar to the Selcall system, DSC uses a different technology and is not compatible with earlier systems. DSC does, however, allow for making direct connections to the land-based telephone system, though facilities to do this will not be available in the United Kingdom.

Maritime Mobile Service Identity

Every vessel with DSC will require a Maritime Mobile Service Identity. This is a unique nine-digit number. The numbers for United Kingdom-based ships will start with 232 and 233. Shore stations will all begin with 00. United Kingdom MMSI numbers will be issued by the Radio communications Agency.

If you know the MMSI of a vessel you are trying to contact then it will be possible to call them up directly using the unique nine-digit code in the same way as one might use a telephone number to contact a individual house. "All ships" calls are also possible and with more sophisticated commercial sets a whole range of calling options become available.

Plans for issuing MMSI's have yet to be finalized in Britain. Options being considered include dealer installation of the unique code after the radio has been fitted or selling equipment with the codes pre-installed but activated only once the set has been licensed. Whatever system is decided upon it is vital that GMDSS radios are properly registered. DSC only transmits the MMSI number, not the name of the vessel. In the event of a distress call the only way to reconcile the MMSI number with the vessels identity is via the list of MMSI numbers held by the Radio communications Agency.

GPS Interface

GMDSS radios (with the exception of small hand-held sets) will have a facility for connection to a GPS receiver. This can either be built into the radio or connected via a NMEA interface. Used primarily for position fixing when sending distress messages the GPS information can be used for a number of other sophisticated functions.

Distress

At its simplest GMDSS will at the press of a button transmit a distress message to "all stations," giving the boat's MMSI number and, if connected to a GPS, position. More sophisticated systems will allow the nature of the distress (e.g. sinking, on fire, etc.) to be added to the message. Commercial ships receiving the distress message are able to relay the message if no acknowledgment is received so it is possible that a weak signal could be relayed to the Coastguard even if the transmitting boat was out of range.

On receiving a distress message, the Rescue Coordination Centre will issue a Mayday Acknowledgement via DSC and reply on Channel 16. Further communications is conducted by voice on Channel 16.

One of the big concerns with increasing leisure use of GMDSS is false alarms. Commercial shipping has produced a rate of false alarms of about one per 20 years per equipment. If this were to be repeated by leisure users in a busy location, such as the Solent, it has been calculated that there could be a false alert as often as once every 15 minutes at busy times. The onus will be on yachtsmen to ensure that this nightmare scenario does not come to pass.

Standards

All the original standards for GMDSS were formulated with commercial shipping in mind. The needs of leisure users were only considered very late in the process and it was quickly discovered that equipment suitable for big ships would not necessarily be appropriate for small yachts. As a result, some additional standards were produced specifically to cover yachts and other small craft. Non of these has yet been ratified as an international or European standard.

In the United Kingdom a specific standard for yachtsmen, MPT 1279, has been produced. When looking to buy new equipment, a minimum standard to look for is MPT 1279. With additional European and international standards for yacht equipment still being ratified, the only certain way to determine if a particular unit is currently type-approved is to contact the Radio communications agency. Licences will not be issued for non type-approved equipment.

Equipment complying with MPT 1279 for use on board yachts is not yet available. Most of the major radio manufacturers are working hard to get equipment approved and it should be available during late 1997.

Operator's Certificates

The course and examination for the VHF only operator certificate will be updated to reflect to the requirements of GMDSS. Short conversion courses will be offered for existing certificate holders.

The Future for Channel 16

Some decisions regarding the future role of Channel 16 have already been made. Starting in 1999 there will be no requirement for commercial shipping or National Maritime Rescue services to listen on Channel 16. The British Coast Guard has indicated that it will continue to listen on VHF Channel 16 "for the foreseeable future," but some European coastal agencies may ultimately cease to monitor what has been known for over 30 years as the "distress and calling" frequency.

It seems almost certain that commercial shipping will cease to monitor Channel 16 just as soon as they are allowed to do so. After 1999 it will be difficult or impossible to contact most commercial shipping without DSC. This will have serious implications for yachtsmen wishing to contact commercial vessels. Perhaps more critically, commercial shipping is unlikely to hear distress messages on Channel 16, eliminating the possibility of a Mayday Relay for voice calls when a transmitting yacht is out of range of a Coast Station.

It is certain that Channel 16 will be retained as the principle voice frequency for distress traffic. Once contact has been established via DSC, subsequent voice communications will be conducted on Channel 16.

There have been proposals — not yet confirmed — to designate Channel 16 purely as a distress frequency at some point in the future. Such a change is not contemplated for a number of years and would only come into effect when a substantial proportion of vessels were equipped with DSC. This would then preclude the use of Channel 16 for calling. Those still wishing to make initial contact on a voice frequency (i.e. non DSC-equipped vessels) would be obliged to use another Channel to make their initial call.

So what should the prudent yachtsman do now? In the short term at least, probably nothing. All existing VHF radios will continue to work in most capacities for the foreseeable future. Those contemplating extended cruising with MF/HF or Inmarsat communications should look seriously at installing a GMDSS controller.