The following article was recently published in Digital Ship magazine.




THE GMDSS – WHERE TO NOW?
 
By G.C. Dunstan
 
 
The focus for maritime communications these days has swung firmly towards Satcom and IP based networking.  Delivery of cost-effective bandwidth to shipping underpins all new developments in the marine communications field.  Many ships are now effectively an extension of the head office computer local area network. 
 
How things have changed from even a few years ago, when telex was the main method of ship-shore-ship communications….
 
Of course, the driver for all this change was the introduction of the Global Maritime Distress and Safety System (GMDSS) in the early 1990’s.  The GMDSS has been with us for more than a decade now.  Has it served its purpose?  Is it moving with the times, or is it stuck in the past, of little use and largely ignored?
 
Has the GMDSS reached its use by date?
 
This article examines the major sub-systems that make up the GMDSS, discusses their effectiveness and proposes some new ideas to revitalize the system.
 
 
Inmarsat C and EGC – the jewel in the GMDSS crown
 
The one GMDSS technology that has been a stand out success is Inmarsat C and Enhanced Group Calling (EGC).  EGC is used for the delivery of Maritime Safety Information (MSI – weather reports, nav warnings and Search and Rescue information). 
 
Like all successful technologies, EGC is a well thought out and simple system.
 
EGC allows the broadcast of MSI to ships in a defined geographic area - this area may be selected as a radius around a position, or a box of whatever dimensions the sender desires. 
 
The method of defining the broadcast area is elegantly simple – each message has a header which lists the geographic coordinates for broadcast.  All Inmarsat C ship terminals are fed with a GPS-derived position, so they ‘know’ their position at all times. 
 
On receipt of an EGC message, the ship terminal compares the position information in the message header with its own position.  If the positions match, the ship terminal prints the message.  If the positions don’t match, the message is discarded.   
 
Inmarsat C is also used for ship-shore distress alerting.  Again, this aspect of the system offers simplicity and reliability.  Users can either send alerts by pressing a single button, or, if time permits, composing a more detailed message.
 
One early problem with Inmarsat C was the high incidence of false distress alerts.  This problem was successfully addressed in two ways:
  The structure of the Inmarsat network allows a very high degree of control over the mobile terminals.  An errant user can be quickly identified and contained, thereby preserving overall network integrity. 
 
 
Digital Selective Calling (DSC) – the black sheep of the GMDSS family
 
One of the great strengths of the GMDSS is the diversity of communication links it offers mariners.  Ship to ship and ship to shore distress alerts may be sent over various satellite and terrestrial radio systems – all one’s eggs are thus not in the same proverbial basket.
 
The satellite aspects of the GMDSS are clearly working well.  Unfortunately, their terrestrial radio counterparts have not been so successful.
 
In the GMDSS, Digital Selective Calling (DSC) is used to automate the transmission and reception of distress alerts sent via terrestrial Medium, High and Very High Frequency (MF, HF and VHF) radio.  A DSC alert is normally followed by radiotelephone communications between the vessel in distress and other ships/coast stations.
 
Many would argue that DSC is a classic ‘camel’ – a horse designed by a committee.  The DSC system was originally intended to automate radiotelephone calls between ships at sea and telephone subscribers ashore.  However, the rapid influx of cheap satellite communications has effectively killed off automated HF radio based telephone systems for merchant ships.  Because of this, the majority of the world’s major marine radio stations have now closed.
 
The result is that DSC is effectively designed around a function that no longer exists.  This is evident in the number of redundant telecommands (functions) incorporated in the DSC standard.  These redundant telecommands serve only to overcomplicate operation for users. 
 
When DSC was designed in the 1980’s, ships still carried Radio Officers.  It is obvious that DSC was originally intended to be operated by a professional communicator.
 
Unfortunately, many DSC controllers are notoriously difficult to operate for a non-technical user.  In addition, equipment operating routines vary significantly from brand to brand, such that a user trained on one type of equipment will have considerable difficulty operating another.
 
So, the net result is that many mariners simply refuse to use DSC.  Marine Radio Surveyors often report finding shipboard DSC systems turned off. 
 
Not surprisingly, the DSC false alert rate is also unacceptably high. 
 
There is no question that DSC, used correctly, is a powerful and effective alerting mechanism.  Ironically, DSC’s effectiveness for long range alerting is compounding the false alert problem. 
 
Ships often receive (invariably false) DSC distress alerts from thousands of miles away.  Whilst this is interesting from a technical perspective, it is a complete waste of time from a SAR viewpoint.  And, of course, incoming message alarms for these useless messages serve only to annoy the bridge staff.  Any wonder Masters and mates are turning DSC off…
 
The IMO and the ITU, to their credit, have issued a revised DSC equipment standard, which removes some of the more redundant functions and addresses many operational problems.
 
However, this standard does not apply to existing shipboard systems, only new equipment.  Most ships are effectively saddled with the dysfunctional DSC equipment they now have. 
 
So, how do we fix the current DSC situation?  Or do we even attempt to fix it at all?  There has been ‘corridor discussion’ at IMO of removing DSC from the GMDSS completely, which smacks of the ‘turn it off and ignore it’ philosophy demonstrated by some ships.
 
Abandoning DSC would be a serious mistake.  As discussed previously, the inherent strength of the GMDSS is the multiplicity of communication links it provides over different satellite and terrestrial bearers.  If one system is down, you always have an alternative.
 
The root cause of DSC’s problems is the lack of a central operational and administrative authority to oversee the system - the operation of DSC systems on vessels is effectively regulated by individual Flag States.  This is clearly not working. 
 
Contrast this to Inmarsat, where central monitoring and mentoring of users is standard operational procedure.
 
Traffic analysis on the DSC channels reveals that poor operating standards predominate.  Ships regularly breach the rules by using the DSC channels for inappropriate messages.
 
I suppose it can be argued that at least some mariners are attempting to use the system…it is just that they are using it the wrong way..
 
What is needed is for some central body to take charge of DSC, and conduct an active monitoring and education campaign.  Modern internet technology allows remote control of DSC shore stations from anywhere in the world.  A number of DSC monitoring stations could be controlled from a central point, to provide world wide coverage.
 
It would be a simple matter to match a ship’s DSC identity number to her Inmarsat number.  Ships which regularly breach DSC operational standards could be sent a polite reminder (or even an operational guide) via Inmarsat.  Repeat ‘offenders’ could even be visited during a Port State Control Inspection for some face to face mentoring and training.
 
This strategy would go a long way to solving DSC’s current problems, and allow the full benefits of the system to be available to all mariners.
 
Over to you, IMO.
 
 
Chaos on the GMDSS radiotelephone distress and safety channels
 
After a GMDSS operator sends his/her DSC alert, he/she then switches to the radiotelephone distress and safety channels and communicate with other ships and shore stations.
 
The problem is that these channels are often plagued by interference.  It is not uncommon to hear the channels being used for long conversations between unauthorised users, particularly at night down here in the South Pacific.
 
Whilst the international radio regulations prohibit interference to distress and safety channels, it seems that many of the stations causing the interference don’t actually read the radio regulations…
 
Again, this problem is directly attributable to lack of regulatory oversight.  All the IMO Resolutions and ITU Radio Regulations mean nothing if they are not enforced. 
 
This problem has been present for at least 10 years.  And, for 10 years nothing meaningful appears to have been done to solve it. 
 
Distress communications will be rendered ineffectual if the distress channels are full of interference.
   
Government run marine radio stations need to take charge of the problem, and clear the intruders off.
 
 
Narrow Band Direct Printing – an obscure name for a little used system
 
Narrow Band Direct Printing (NBDP) is an IMO-esq term for plain old radio telex.
 
In the GMDSS, NBDP is designed to be used for communications following a DSC distress alert, and also for the broadcast of MSI into Sea Area A4 (the Polar Regions north of 70 deg N and south of 70 deg S).
 
HF radio is the primary alerting mechanism in GMDSS Sea Area 4 because of a lack of coverage from the Inmarsat satellite system.
 
The original intent of NBDP was to provide on-going text based distress communications to those mariners for whom English is a second language.  However, to this writer’s knowledge, NBDP has rarely, if ever, been used for this purpose. 
 
The practicalities of a distress situation dictate that radiotelephone is the mode of choice for on-going distress communications – it is a lot easier to speak into a microphone than type on a keyboard.  Most GMDSS courses discourage use of NBDP for this reason. 
 
Moreover, an NBDP terminal has very little commercial use these days.  Few coast stations offer commercial radio telex services.  The great majority of commercial HF marine data communications (from Globe Wireless, etc) use email type protocols which are not compatible with NBDP, and require a separate terminal.
 
Thus the NBDP terminal sits in the corner of the bridge, gathering dust….. 
 
The IMO has recognised the shortcomings of NBDP, and is proposing deleting it as an option for GMDSS Sea Area A3 (the world’s open ocean areas).  At the moment, it will remain a requirement for ships sailing in Sea Area A4.
 
There are moves to replace NBDP with a commercial email-like data protocol; however this is still being discussed at the IMO and the ITU. 
  
   
 
GMDSS – a true global system?
 
Many have argued that the GMDSS is a system suited primarily for developed nations.  The system appears not to be well aligned with the needs of the developing world, particularly those countries where smaller vessels predominate. 
 
To date, the great majority of the world’s recreational craft and commercial/fishing vessels under the 300 GRT SOLAS cut-off have not embraced the GMDSS.
 
Whilst the theory of one universal global maritime communications system is sound, the implementation of the system has been less than successful.  For example, Flag States are left to determine their own requirements for vessels not covered by SOLAS – i.e.: those engaged on domestic voyages and those vessels under 300 GRT, engaged on an international voyage. 
 
Despite the strong recommendations of IMO, many Flag States do not require GMDSS compliance for non-SOLAS vessels.
 
This non-compliance presents serious shortcomings for small ships operating in the vast expanses of the Pacific and Indian Oceans, where voyages of thousands of miles are often undertaken.
 
Under the pre-GMDSS radio systems, all ships were required to maintain watch on two radiotelephone channels - channel 16 VHF and 2182 KHz on MF.  This system effectively provided communications interoperability between all classes of vessel, large and small.
 
The IMO has extended the requirement for merchant vessels to maintain the short range channel 16 VHF radiotelephone watch.  However, the 2 MHz medium range compatibility provisions have not been continued under the GMDSS – the old 2 tone radiotelephone auto alarm has been replaced by DSC.
 
The result is that there are often no direct communications available between GMDSS and non-GMDSS vessels outside of VHF range (about 20 nautical miles). 
 
This incompatibility between GMDSS and pre-GMDSS radio systems means that a merchant ship can sail relatively close by a small vessel in distress, (and vice-versa) without receiving any alert.
 
If the GMDSS was working as intended, suitability equipped Coast Radio Stations would be able to relay alerts between GMDSS vessels to their non-GMDSS equipped counterparts.  This would solve the interoperability problem.
 
However, this solution requires that GMDSS-compatible shore infrastructure be in place in all areas of the world.  Unfortunately, many Coast Stations in the developing world have not been upgraded to GMDSS standard because of the apparent high cost.  

In many parts of the world, there are effectively two separate maritime safety communication systems running in parallel - which are largely incompatible.
 
The problem is exacerbated by the separation of commercial and distress/safety functions brought about by the GMDSS.
 
Under the pre-GMDSS Morse Code and Radiotelephone systems, the distress and safety services provided by Coast Radio Stations were subsidised to a certain extent by revenue from commercial traffic (i.e. telegrams and telephone calls).
 
The GMDSS has transferred the great majority of the world's maritime commercial traffic to Inmarsat systems.  Accordingly, many Coast Radio Stations are now forced to rely directly on funding from their Governments and SAR agencies.  Unfortunately, some developing countries have precious little revenue to allocate to marine radio networks.
 
Even Coast Stations in developed countries are feeling the effects of the GMDSS - many of the world's major Coast Radio Stations have closed or severely rationalised their services.  Some countries are now providing SAR-related services only from their stations.
 
However, all is not lost on the Coast Radio Station front – developments in technology mean that cost-effective stations can now be established for a much reduced outlay.
 
 
Promotion of GMDSS to recreational mariners
 
The GMDSS is a global system in name only.  Despite what many think, the system is not just intended for merchant ships - there are GMDSS technologies available for everything from a small run-about to a VLCC.
 
Promoting the GMDSS to recreational users, particularly the most suitable technology - VHF DSC - is a classic Catch-22 situation. 
 
Users are reluctant to fit a new VHF DSC radio unless there is compatible shore infrastructure in place to receive their calls. 
 
Some administrations seem strangely reluctant to encourage the take up of VHF DSC by recreational users.  There is an unexplained resistance to the installation of VHF DSC shore stations in some parts of the world, particularly Australia. 
 
Interestingly, the price of VHF DSC radios suitable for recreational craft is steadily decreasing, with new equipment now becoming available for less than $500 US.  This low price will eventually drive up the market penetration of VHF DSC to the point where installation of shore base stations will become a necessity.
 
 
 
AIS and GMDSS
 
One area which promises some interesting new developments is Automatic Identification Systems (AIS).  Although strictly not a GMDSS system, the line between AIS and GMDSS is becoming increasingly blurred.
 
At the forefront of new AIS-related technologies is the so-called “AIS SART” (Search and Rescue Radar Transponder).  These are intended to replace the current SART system, which operates in conjunction with an X band marine radar. 
 
Existing SARTs haven’t been overly successful, as they rely on an X band radar being in range.  As X band radars operate in the 9 GHz band, range is limited, and performance can be affected by rain and intervening land masses.
 
An “AIS-SART” is essentially a small portable version of a shipboard AIS, with an inbuilt GPS receiver.  The beauty of this system is that, as it operates in the VHF band, it provides far more range than a conventional radar-reliant SART, and is not affected by rain or terrain (provided the land mass is not too high, of course).
 
 
A scorecard on the GMDSS
 
In conclusion, the obvious question arises – is the GMDSS an improvement over its predecessor systems?
 
The answer is, or course, a resounding yes.  Ships have access to instant communication technologies that have undoubtedly saved many lives.
 
The GMDSS is not a perfect system – the principal problems being the lack of sufficient shore radio stations for many areas of the world and the ongoing issues with inappropriate use of DSC and radiotelephone channels. 
 
If these problems are left unchecked, they have the potential to seriously undermine the system and compromise the safety of mariners.
 
However, with a bit of strategic thinking from IMO, we can refine the GMDSS into a truly global marine safety system for all.
 
 


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