AIS saturation

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alan17

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AIS on small boats

Last weekend I was saling in the Brightlingsea/Bradwell area and as usual there were a number of yachts out racing.

Especially when single handing I find AIS a useful extra pair of eyes that do not get bored and loose concentration.

The "dangerous target" alarm sounded and as usual I looked around for a large vessel and found none so I went below to check the details. All that was visible on the screen was the normal triangle but no data. It became clear that the signal was from one of the racing yachts not from a container ship or large freighter.

I have come to the conclussion that if many small yachts etc fit AIS transceivers it will in my opinion devalue AIS. If for example all the yachts over say 25 feet racing in the Solent were to be equiped with AIS trnsceivers the entire screen would be filled with little traingles.

I would welcome other forumites views.
 
I hear tell of another yachty sailing in the Brightlingsea/Bradwell area who was complaining about a Southerly 100 who caused him panic and consternation last weekend.

He was heard to say that he wished all other yachties removed their AIS so he could sail peacefully in the knowledge that the ony time the alarm would sound was when he was being approached by a ship "Constrained by Draught" and not another silly small yacht!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
 
Agree entirely. I have had an AIS receiver for some time and find it a useful aid. The only way that it should be allowed for small craft is if there is a way to configure your receiver to ignore all targets under a certain size.

It could be argued that in already crowded waters, such as the Solent, or many other close-to-harbour situations, you could just turn off your AIS receiver since you would be maintaining a particularly vigilant watch in any case. On passage, the problems with many small targets would not be so great.

As an aside - we also have to start worrying about the supposed military experiments with creating many false AIS targets from a single ship - to confuse the enemy I guess!
 
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It could be argued that in already crowded waters, such as the Solent, or many other close-to-harbour situations, you could just turn off your AIS receiver since you would be maintaining a particularly vigilant watch in any case.

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Tell that to the crew of the Ouzo

IMHO the use of AIS transceivers by craft smaller than 100ft should be banned.
 
Its a big difference sailing during the day, you dont need an AIS, MARPA or indeed anything other than a mark 1 eyeball if the vis is ok, at night different matter, if my memory serves me, the vessel involved in the Ouzo incident had just made a course change prior to the incident, perhaps the guys on Ouzo thought that they were in the clear until that point and then they were unable to do much about it, AIS or MARPA might have helped. I dont see the point in turning on AIS or MARPA during the day whilst swaning about in the solent or indeed anywhere else
 
Like most things - you need selective filtering ...

you'll want all AIS targets if you're down below for a minute ... but only the bigger stuff when on deck - even then you might not really care about it and only want a 10 second warning that it is in range ....

At the moment you get alarmed on just about everything - the controls for that alarm need to be more detailed ... same with DSC alerts ... I really don't give a stuff about the french DSC alerts if I'm not going across the channel - but my VHF doesn't know that - so I need to be able to programme that in ....
 
Under the current state of affairs I think you're right - AIS could be devalued by too many targets, but I also think the AIS platform will prove to be versatile enough to cope.

I Echo Fireballs call for filtering - but it's still relatively early days for AIS B and i'm sure these are developments that will be implemented on future systems - or when the next software updates rollout. Raymarine plotters already give the option of only displaying dangerous targets, so there generally isn't too much clutter, and i imagine other manufacturers have similar options.

Since ships already have the capability of switching off reception of class b targets (which I don't think i just imagined) then surely it's just a matter of a few lines of code before we can do the same. (or maybe better, with seperate class A and class B alarm settings).
 
I disagree with the ban AIS transceivers on smaller vessels view. If you're putting around the solent, why are you bothering with AIS? You wouldn't have the radar on either. Now sailing across the biscay, cross channel or even on a long coastl passage I don't mind seeing all the targets (particularly at night).
 
While I sympathise with anyone who has to sail on the solent we need to be careful not to loose a sense of proportion. The solent is one very small confined area crowded with both comercial and leisure traffic from a large number of habours. In fact it would not be unresonable to consider the whole area inside the isle of white as effectively 'in habour'. I can quite see that in such a situation if lots of the leisure vessels fit AIS B then they system will become so overcrowded as to be vertually usless.

In normal circumstances (ie outside a very frew exceptionally crowded hot spots) however this crowding is never going to happen and the system could be very usful in allowing ships to see where leisure vessels are. I agree thet as a principle small boats should try not to impede large vessels whenever possible by avoiding close quaters with them. To this end a recieve only AIS system is ideal, for example in assisting a yacht crossing a shipping lane or in open waters where vessels maintain a steady course. There are circumstances however where this may not work. Two that spring to mind are when a yacht is hove too in bad weather, perhaps with drag deveices deployed and therefore unable to manover. In these circumstances it is also very likely that the yacht will not show up on radar due to sea clutter and AIS may be the only reliable system for a large vesel still under way in those conditions to 'see' a yacht. The second is when entering an esturary. Because ships may becomming from several directions and manovering into more than one channel there is an area where it can be very difficult to predict where ships are going. With the speed an size of many large vesels it is quite possible for a yacht to suddenly find that not only has a ship turned on to a near collision course but that it is approaching so fast that there is almost nothing the yacht can do. The ship is probably totally unaware of the yacht as it is below its bow out of both visial and radar sight howeverit would still show as an AIS target.

While I would not want to rely too much on any system that relies on someone else acting to ensure my safety I think AIS could become a useful aid and get a bit fed up with so many people knocking it because it might not work in the solent. NOTHING will work in the solent, if you have to sail there take a sedative and keep your eyes peeled. I worry that because there are so many people who do brave this bit of water they effectively have a very loud vioce which may lead to restictions to a system which, for the rest of us, could be very useful. The solent already has special regulations to seperate traffic so perhaps the answer is to restrict the use of AIS B under the same regulations but only for areas like the solent and perhaps a few other south and east coast spots, leave the rest of us free to use it.
 
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In fact it would not be unresonable to consider the whole area inside the isle of white as effectively 'in habour'.

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For the purposes of Solas V, most of the Solent is regarded as within harbour restrictions, and is outside many of its regulations for passage planning etc.
 
IMHO the use of AIS transceivers by craft smaller than 100ft should be banned.
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I think there are some circumstances where theoretically AIS B could be useful but there are flaws in it's thinking. I thought very carefully before installing my new AIS (reciever only) My conclusions were.

1. Most ships have the ability to switch off B and probably will.
2. If we all fitted one it would cause chaos as most people will transmit constantly and not switch off when in places like the Solent.
3. An alarm for a midget is not discerned from an alarm for a monster so switching off all but "dangerous" targets does not help. You could ignore a tanker and get alarms from a 20 ft yacht.
4. Most yacht recievers don't have the ability to reject B so the whole system could be cocked up for yotties if we all fitted B. Ships will ignore us and we will not be able to use it effectively to avoid monster trucks ourselves.

This to me means that AIS B is a non starter and will probably die a death anyway.

Since I have fitted it I have come to the conclusion that the alarm settings need setting up very carefully anyway. With a 5 mile danger zone I got an alarm from the Pride of Bilbao docking in Portsmouth when I was sitting on my mooring in Fareham!
If every small yacht had one I would get alarms all the time every time some booger tacked within my exclusion zone!
 
We were sailing in the same area on Saturday/Sunday, but we have a switch on our AIS so that we can use it only when we need to. It was switched off all weekend - therefore no problems at all.

For those of us who are fortunate to sail on the east coast (Essex/Suffolk area), AIS is useful crossing the Thames, the approach to Harwich and the North Sea, and probably at night. At other times, save power and sanity!
 
We do sail the solent ... and I partially agree with your comment about AIS in the solent ... but not totally ... we (now) use AIS to identify potential problems long before they become an issue - we can watch ships coming round the NAB, with a name we can usually guess if they are going into Portsmouth or on to Southampton - it means we can alter our passage so we don't have to do wild alterations at a moments notice later.
The issue will be if AIS-B clutters this up so much that our un-intelligent plotter cannot give us the info we want - at which point we might as well turn it off.
No, we don't NEED AIS in the solent, but it can make the trip a little easier....
 
I have come to the same conclusion as Boatmike, and see no point in fitting an AIS B for my sailing, which is mainly in the Solent area.

I do, however, have an AIS receiver, connected to the chartplotter mounted in the cockpit. This I find very useful, providing me with a little bit more awareness of other traffic.

I do not use any automatic alerting, prefering to reconcile each AIS target with the real world around me, and make my own judgement as to what needs to be avoided.

John
 
I may have dreamt this, but I thought that the NASA receiver had the ability to switch between A&B, A only or B only. Wouldn't switching to A only solve this?
If the NASA unit is at the cheaper end of the market for receivers then I would guess the more expensive models have the same ability? Maybe not.
 
You're confusing the ability to switch between the 2 AIS transmission frequencies with the transmitting vessel type.

The NASA AIS engine does not offer the ability to filter out transmissions from class-b devices.

Rick
 
A few points from the "big ship" point of view...

AIS B transmissions can be useful, in the right place. Mid channel, open waters, etc. Yes we do filter it out in the Solent, but then it wouldn't help anyway - we have pilot, master and 2 OOW on the bridge, with ABP launch and escort tug with us.

AIS B will not "die a natural death". The introduction of AIS had nothing to do with marine safety (long term) - it is about identifying and tracking vessels, initially for port control purposes but think about the potential to make compulsory then link to licencing / charging...

AIS, like anything, is an aid to navigation not a means of navigation - use sparingly in the right circumstances but don't rely on! Nothing replaces a good visual watch system supplemented by radar use in appropriate conditions.

Anyway, it can never be as bad as the early days of DSC when a mayday inthe Solent could trigger hundreds of "relay" calls within minutes...
 
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