AIS

[Sans Bateau]

I can see no point in a sailing boat or power boat needing to transmit an AIS signal in the confines of somewhere like the Solent, as for leaving it switched on when in the marina, just beggars belief. It comes under the heading 'I have a toy, it must be used'.

However, once out in open water, crossing the channel, Lyme bay or some TSS, then AIS transponders are a valuable asset.

 

[timbartlett]

...I can't honestly see any significant benefit to small yachts having a transponder on all the time whereas I can see many problems. It may seem reasonable to those that use them but if the end result is worse outcomes for everyone then it is not a sensible use of technology.

Interesting POV.
There was a somewhat similar situation a few years ago, when the high number of false distress alerts generated by epirbs were causing problems for the SAR authorities. Obviously the best way to resolve the problem would be to reduce the number of EPIRBS.

But does this mean that any individual was wrong to carry an EPIRB?

Similarly, large numbers of AIS transponders may cause local problems in a very small number of very small areas. But does that necessarily mean that people should be discouraged from using them?

I don't believe it does. We have been crying out for a means of making ourselves more visible to ships for donkey's years. Our navlights are rubbish, and radar reflectors don't work. Let's not kick AIS Into touch because it works too well!

The emphasis IMHO, should be on decent filtering at both ends -- turn the that you transmitter off when it serves no useful purpose, and filter the incoming data so that it doesn't alarm for stationary targets that you aren't going to hit!

 

[Skylark]

The world is said to be covered 75% by water. The unbelievably congested waters of The Solent must account for a miniscule amount of that 75% so IMHO, carriy no weight to any objective argument. AIS is undoubtedly a very worthy addition to SOLAS. I have chosen to buy a class B transponder for my own vessel and I now consider it as invaluable.

It could be considered that anything beyond lead line, log, compass and time piece is non-essential. I sailed this past weekend out of the Solent for only the second time in my career. The charter vessel did not have AIS but we crossed the Channel in complete safety without it. As the stand on sailing vessel, commercial traffic on a number of occassions manoeuvred around me. In the heavy seas, my experience is that AIS gives certain advantages over radar (locking on to target, for example). It also has some disadvantages and like all equipment, requires knowledge and experience to understand its strengths and weaknesses and to get the most from it.

 

[pmagowan]

Tim, I don't get your analogy with epirbs. It is a quite different situation. If you have epirbs going off accidentally all the time and causing confusion amongst search and rescue the solution is to better design the epirbs and have a method of checking if the activation is intended (mobile No., MMSI etc). I dont have an epirb but I can see that they are becoming a more a nd more useful piece of kit when it comes to activating the rescue services.

The AIS is different. It is an aid to safe passage and collision avoidance. If its use increases the risk then it needs to be examined and some reasonable guidelines for its safe use determined. I can see how filtering etc may help but you then run into the problem of everyone is filtering out small boats and you are in the same situation as if you had no transponder.
By transponding you are determining that other vessels may benefit from having your position and details displayed on their screen. In many circumstances this assumption will be incorrect. If you cry wolf too often people will not listen. All my experience of AIS which is actually in quite quiet seas and even here small boats transponding only seem to complicate things without (IMHO) improving their individual safety.
I think transponding should be reserved for times when you may have difficulty manouvering, are in an area of high commercial traffic or you are far out to sea and your watch is a bit lax. I think always-on transponding will just erode the purpose of the system until it is useless.
Perhaps if a commercial ship crew member was about they could give their opinion.

 

[timbartlett]

[/QUOTE]

Tim, I don't get your analogy with epirbs. It is a quite different situation. If you have epirbs going off accidentally all the time and causing confusion amongst search and rescue the solution is to better design the epirbs and have a method of checking if the activation is intended (mobile No., MMSI etc). I dont have an epirb but I can see that they are becoming a more a nd more useful piece of kit when it comes to activating the rescue services.

My point is that EPIRBs became a nuisance because there were lots of them. But none of the individuals that had bought one was being a nuisance: they all (probably) believed that they were taking sensible precautions to protect their families and crews. Similarly with AIS: collectively they may be seen as a nuisance, but individually every one is based on a valid safety decision.

The AIS is different. It is an aid to safe passage and collision avoidance. If its use increases the risk then it needs to be examined and some reasonable guidelines for its safe use determined. I can see how filtering etc may help but you then run into the problem of everyone is filtering out small boats and you are in the same situation as if you had no transponder.

I don't see how AIS can be accused of increasing the risk. Even if, as you suggest, ships were able to "filter out" all small craft, I don't see how that makes us any less visible than choosing to filter ourselves out by switching the transmitter off!

But that assumes a very crude kind of filter. (I don't like the word "filtering" BTW, because it leads to discussions like this, but unfortunately it seems to be standard) If I am driving a boat, I don't think to myself "it's OK to hit that one because it's only an Optimist, but I don't want to hit that one because its a Swan 56". My "natural filter" makes me pay less attention to boats that are stationary, that are moving away from me, or that are not likely to pose a collision risk for any other reason. That is "intelligent" filtering. It is available on many yachtie AIS systems, and it is compulsory on the latest generation of ship systems. i.e. it suppresses contacts that are not a collision risk, and by doing so highlights those that are a collision risk. And it highlights them whether they are big, or small, AIS A or AIS B.

By transponding you are determining that other vessels may benefit from having your position and details displayed on their screen. In many circumstances this assumption will be incorrect.

So if you switch on your navigation lights, are you "determining that other vessels may benefit?" Can you think of many cases in which that assumption would be wrong? Is it "crying wolf" to switch on your navlights?

Perhaps if a commercial ship crew member was about they could give their opinion.

This thread started with a quote from an article in the Royal Institute of Navigation magazine, written by a Southampton pilot. His conclusion was:
"To summarise, while AIS is undoubtedly a help to keeping a proper lookout at sea, it is only of benefit when appropriate to the prevailing circumstances and conditions. Because of both the slow refresh rate of AIS B information and the multiplicity of transponders in congested waters, the navigator or pilot is unlikely to use AIS. Like the first voyage cadet, he or she will be keeping a lookout by sight and hearing and radar." It can only be a benefit if other vessels transmit: if they fail to do so, it loses its value. When the Master or Pilot decides that it is of no value, he stops using it. I don't see that it is up to us to second-guess his decision.

That is not to say that I support people who keep transmitting even when their boats are safely strapped to a marina pontoon. But I'm inclined to give them the benefit of the doubt and assume that they just forgot to switch it off!

 

[pmagowan]

in reverse order.

No prob giving people the benefit of the doubt. If it bothered me that much I would pop round and tell them they were still transponding.

I think prevailing 'circumstances and conditions' is the important part, my main problem is with the always on situation. I have listed a number of situations where I would be happy to transpond if I had the ability

I think you are being a bit pedantic re Nav lights but perhaps my argument sounds a bit pedantic also. I think there is a clear difference in making yourself visually apparent as the commonly understood rules suggest and transponding to someones screen. To turn off nav lights would be like actively trying to hide while to stop transponding would be seen as appropriate in many situations. Just because you have the ability to tell someone precisely where you are doesn't mean that that is necessary. It can all become 'too much information'.

Your intelligent filtering is a good idea and if every system had an infallable version of this it may remove the problems. Until then it may be easier to switch off when not required.

It is dangerous if by bombarding people with information they become desensitized to it. It is not an 'individual' error but a system error. The current system would have everyone ignoring their AIS due to continuous alarms.

I understand your point re epirbs but i consider them not to be comparable on equal terms. The clear solution to epirbs was to make the system better not to stop people using it at all. Similarly with AIS a better 'system' would be for people to use them with thought and perhaps guidelines, perhaps until a sooper dooper device came out which take away the difficulties mentioned.

As I said, I sail in quiet waters. It poses very little concern or problem to me. I just note that a perfectly good device can have a flaw in how it is used. The solution, change the device or change how it is used, or both.

Makes us all safer!

 

[timbartlett]

Your intelligent filtering is a good idea and if every system had an infallable version of this it may remove the problems. Until then it may be easier to switch off when not required.

Sorry, can't take credit for that idea! The current regulations for new compulsory-fit AIS installations on ships include a compulsory requirement for filtering to be available. Filtering suppresses targets from the display, but does not "ignore" them. There is also a requirement that "dangerous" targets must not be suppressed (i.e. the system must reveal a target that becomes dangerous even if it was once suppressed.)

And there are some excellent yottie AIS systems around that also incorporate decent filtering.

So the systems are being improved. Of course it will take time.

Hell, people are still trying to make a radar reflector that actually meets the performance specifications. They've been working on that problem for 60 years and still can't do it!

 

[Elessar]

Sorry, can't take credit for that idea! The current regulations for new compulsory-fit AIS installations on ships include a compulsory requirement for filtering to be available. Filtering suppresses targets from the display, but does not "ignore" them. There is also a requirement that "dangerous" targets must not be suppressed (i.e. the system must reveal a target that becomes dangerous even if it was once suppressed.)

And there are some excellent yottie AIS systems around that also incorporate decent filtering.

So the systems are being improved. Of course it will take time.

Hell, people are still trying to make a radar reflector that actually meets the performance specifications. They've been working on that problem for 60 years and still can't do it!

so it must reveal the tug......

Committee designing the rules maybe?

Agree about filtering though. My Raymarine/Nasa system is of limited use in congested waters. I leave it on receive but turn off the audible alarm. The thing that makes it useless is that you cancel an alarm on a target, but it will repeatedly re-alarm that same target, not ignore it.

And typical raymarine, I don't think boaters design their software. If I had 2 sofkeys ie clear alarm / switch off alarms that would be better than nothing, but the switch off alarms function is buried deep in a menu, not what you want to do when mooring for example. So the alarms stay off.

 

[tcm]

The pilot is a fool IMHO if he thinks AIS bit useless in confined waters.

In confined waters AIS allows you to id the existence of a boat, and its name, and status. You can even do this at night, or in thick fog. Just two days ago, at night, i called up a 300ft coaster on vhf - "Vot eez problem?" "You have no lights on". I only "saw" him (and his name) cos he had AIS.

I agreed with an earlier Bartlett idea - more than 1 tonne the manufacturer shd fit AIS. If it's cluttered you're looking at the wrong magnification. And/Or - it's very cluttered! So deal with it! Frinstance - Anyone know of some small sailing boats run down in and around the solent? Hm? Did they have AIS? Don't think so. It would have saved them.

 

[pmagowan]

Exactly Elessar, There is a system error where the effectiveness is greatly decreased. I really think it would help if there was a guideline for appropriate use of transponders.

The intelligent filtering is fine, if it works, and if it is widely adopted. I still think you will have a lot of false alarms. Any system where false alarms are high will have severely reduced effectiveness due to human nature to ignore.