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AIS: Your feedback

AISYour feedback to the RYA Cruising News article: AIS transmissions from small craft.

Thank you for your overwhelming response to September's article in Cruising News, AIS transmissions from small craft. 

It was very interesting and very useful to read your comments and thoughts on how you are using AIS, and what you consider to be its misuse.    

It has not been possible to print all your comments; however, there were a couple of recurring themes through your emails which we felt should be shared.  


Most of you were concerned about level of clutter on the screen caused by large numbers of small recreational craft transmitting in inshore areas where it was considered that this was not necessary.   

Here are extracts of some your views on this:  

‘We spent the summer in the German Baltic waters, where the majority of small vessels have AIS transmitters. The result was clutter on the screen. 

'I have little interest in detecting another sailing yacht – I do, though want clear warning that a large ferry is heading my way. It would be helpful if small vessels (voluntarily) keep their AIS transmitter switched off, except in the rare cases when it is actually beneficial’.   Gordon Davies  

‘I have an AIS receiver on my yacht…I find the constant use of Class B transponders by small boat owners to be highly irritating and if I had the ability to filter out the Class B transmissions I would.

'In particular there seem to be several boat owners that insist on leaving their transponders on whilst berthed in their marinas…’   David Foster  

‘Interesting article. As a leisure boat owner I am interested in the “big stuff” not a marina full of other leisure boat owners.  In the Solent my own AIS receiver with no filter for Class B transmissions is already cluttered to the point of being almost unusable (except on high zoom) a situation that is likely to get much worse.  

‘Responsible owners of class B transmission equipment should use it judiciously (in shipping lanes etc.)…’ David Goddard  

‘…In busier, more congested waters (the Solent) AIS B presents too much information. Being in the cockpit keeping a good lookout is the best means to avoid accidents and it is not necessary to know the name, course and speed of every small boat within five miles.   

‘We need to try and educate yachtsmen to remain in the silent mode unless there’s good reason to be seen…Only then will there be no excuse for the big ships to filter Class B transmissions out’. Pat Manley    

I asked Stuart Carruthers for his view:  

'I agree with members that we do need to think about when transmitting an AIS signal might be useful.  When we are crossing busy shipping lanes or cruising through known trade routes then it makes sense to switch it on. 

However, when cruising on inshore waters, or cruising through areas such as the Solent then we have to ask is it really necessary? Is it really benefitting me or others?  As many of you agree, AIS is only an aid to navigation; it is not a panacea, no matter what the advertisements say.

It is worth remembering that large shipping does not make big corrections in course that are necessarily obvious to the recreational boater.  Taking regular hand bearings still remains the best way to truly ascertain whether you are on a collision course with another vessel.  

Some members mentioned that they only receive AIS transmissions and do not transmit as they wish to monitor shipping movements in busy waters.

I agree with the view that the more we transmit unnecessarily the more likely it is that Class B transmissions will be filtered out by large shipping which would defeat the point of us fitting Class B in the first place.  

Navigation status

'Class A transponders have, I gather, the obligation to vary the “navigation status” (underway using engines, at anchor, etc.). Class B transponders do not have this.

'I would like to see that added as a future requirement– particularly to discriminate between sailing vessels sailing and motoring (motor sailing). Automatic switching of status could occur by a connection to the engine ‘ignition’ switch. I know there is no ‘space’ allocated for additional parameters, but the ‘ship type’ field, sent as Class B Message 24 every six minutes, and could be redefined for this purpose.  

'It seems pointless, indeed possibly criminally misleading, to broadcast one’s ship type as “sailing vessel” when one is motoring or motor sailing!   I think one should think of three items whenever starting or stopping the engine on a yacht: steaming light, motoring cone and AIS navigation status. Bill Lawrence  

Stuart Carruthers responds:

I agree, You cannot assume that the vessel receiving your transmission will  recognise whether a sailing craft is underway under sail or power for the purpose of the ColRegs.

It will only identify that you are a small craft and your course and speed over the ground.  Lights in restricted visibility (rule 20) provide vital clues as to your status, as does the almost forgotten motoring cone when visibility is good.  

Many thanks once ahain for all your emails. 
The Editor, RYA Cruising News enewsletter

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