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Old 18-05-2013, 11:33   #256
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Re: Please turn your AIS off when docked/moored/anchored

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Several countries require AIS on all recreational vessels,
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Originally Posted by Kettlewell View Post
Which ones?
Singapore for one:


The Harbour Craft Transponder System (HARTS) allows harbour craft within Singapore to be tracked for security reasons. All powered harbour craft must be installed with either HARTS or AIS.

Harbour Craft Transponder System (HARTS) enables the automatic identification of all powered harbour and pleasure craft plying in Singapore waters. This allows the security agencies to focus on craft without an identification tag.

The objective is to enhance the security of Singapore’s port waters.

Requirements
All mechanically propelled harbour craft are required to be installed with the HARTS transponder.

Craft must have a transponder fitted before they can be registered as a harbour and pleasure craft.

Craft with an Automated Identification System (AIS) are exempted from the installation of HARTS as the Authorities are also able to monitor the movements of craft.

Operational area of HARTS
The operational area is the Singapore port waters. The craft owner has to ensure that the transponder is turned on and working when the craft is operating within Singapore port waters.

The HARTS transponder is not required to be turned on when the craft is tied up at a jetty or wharf within Singapore port waters. However, the craft owner has to ensure that the transponder is turned on and working before proceeding out to sea.
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Old 18-05-2013, 11:47   #257
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by estarzinger View Post
*** Edit to Paul's point . . . I agree that I don't know who's or what signals were causing this specific problem. Factually it happened and Veper says it happens. It was the middle of the night so it was most probably NOT underway class B's. I discussed this with Vesper and my impression is that it was an aggregate AIS frequency noise level that was causing it. At the time one of the Vesper diagnosis screens was showing -80db noise while it is normally about -115db.
OK, this could be a "commons" issue. Class-B transponders do share the limited resource of left-over timeslots. But, let me point out that in your original request, and your follow-on "commons" analogy, you never mentioned your inability to transmit. The original problem was strictly about receiving too many unnecessary AIS signals.

As for noise floor, I question the "aggregate AIS frequency noise level" theory. I will look into that, and if I discover something interesting I will report back, but there are plenty of other likely reasons for a temporary / local high noise level.
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Old 18-05-2013, 11:56   #258
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Re: Please turn your AIS off when docked/moored/anchored

Noticed this article on AIS Information Overload. It quotes the founder of Vesper too.

This paper indicates there are discussions about channel overload and what to do about it.
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Old 18-05-2013, 12:01   #259
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Re: Please turn your AIS off when docked/moored/anchored

In the area I'm working at the moment, there is not a great number of pleasure boats to contend with, and presently AIS transponders on these craft is not yet common place.
I can foresee an issue such as coming into Peterhead harbour, where, if the boats in the marina had left AIS transponders on, it could be a distraction.
I would typically have our AIS alarm set to say CPA 1.0', and TCPA at 20 mins. At 5 miles out from the harbour, any boat tied up in the marina with transmitting AIS would activate the alarm.
Our system only has the ability to filter out Class B targets, there is no filtering based on speed. If another few moored boats then set off the alarm, it might be a case of activating that filter, and in poor vis, we may just miss spotting that one class B fitted boat making its way out through the breakwaters.

As you say Mark, the answer is in better filtering, but I wonder if there is an issue with over filtering and rendering the system useless, so that's down to the user, and in that case, are users going to have to undergo some sort of formal training in the use of AIS.

As to the purpose of AIS, I was always under the impression that it was to provide information to other ships, shore bases, and aircraft. I'm certain that the primary purpose of AIS is not as a means of collision avoidance. In the UK, the Maritime and Coastguard Agency stance is that AIS can be used to assist in decision making in collision situations.
For more info see
Guidance & Regulations

Please note, this is the UK's MCA view on the use of AIS.

Cheers
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Old 18-05-2013, 12:16   #260
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I have followed this thread to see how it ended.


There are two views, the OP's of don't clutter everyone's AIS with unnecessary data.

The other, "I will do what I please...." The follow-up to this is large vessels will start to just ignore Class B transmissions. Lets think about this, if Class B devices so clutter Class A devices with useless data and these large vessels start to ignore Class B devices. How long before the first collision that AIS could have prevented?

IMHO the OP had it right, turn the thing off when not underway, that would include when in an designated mooring field.
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Old 18-05-2013, 12:26   #261
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Re: Please turn your AIS off when docked/moored/anchored

Pardon me if I'm missing something here, but it seems that the overload situation is already here for the professionals, they're filtering us little guys out, and for good reason, IMO.

So, why, exactly, is there not the overload situation Evans described? Please make your explanation clear, as I am not technically adept.

I'm going to 'fess up here, when we hear from the more experienced cruisers, and they all seem to think Evans' suggestion was a good one, AND lacking technical expertise, why should one not just turn the AIS receiver off [as was politely requested before all the acrimony started] when one is not using it?

Thanks,

Ann
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Old 18-05-2013, 12:40   #262
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Re: Please turn your AIS off when docked/moored/anchored

This whole problem reminds me of the '70's when everybody had a CB radio.
At first, it was a convenient thing to have to communicate.
As more people discovered CB, it got to be a PITA to use.
In the end, it became so bad the only people using them were ones using illegal high power amps and talking trash.
I hope AIS doesn't go that way.
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Old 18-05-2013, 12:53   #263
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Quote:
Originally Posted by senormechanico View Post
This whole problem reminds me of the '70's when everybody had a CB radio.
At first, it was a convenient thing to have to communicate.
As more people discovered CB, it got to be a PITA to use.
In the end, it became so bad the only people using them were ones using illegal high power amps and talking trash.
I hope AIS doesn't go that way.
No it's not that; I find the comparison with the WWW much better: it started with one website then two then at some point two sites had the same kind of info and people asked one to be taken down because their info was polluting the net, then there were 1,000 sites with the same info and people got scared. Then there were 1,000,000 sites with the same info and then there was Google to make sense of it.

I know, I know, I had left the field...

While I make room again: you all should read Paul Elliot's posts better because he got it right, must be a tech geek I think
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Old 18-05-2013, 13:16   #264
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by s/v Jedi View Post
No it's not that; I find the comparison with the WWW much better: it started with one website then two then at some point two sites had the same kind of info and people asked one to be taken down because their info was polluting the net, then there were 1,000 sites with the same info and people got scared. Then there were 1,000,000 sites with the same info and then there was Google to make sense of it.

I know, I know, I had left the field...

While I make room again: you all should read Paul Elliot's posts better because he got it right, must be a tech geek I think


And Nigel.

A fair bit of the driving force behind this thread seems to be "DON'T TELL ME WHAT TO DO!!" but keep it going, along side there's a lot of very interesting stuff.
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Old 18-05-2013, 13:29   #265
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Re: Please turn your AIS off when docked/moored/anchored

One more geeky point:

When not moving, Class-B vessels only transmit their position (dynamic report) at three-minute intervals, and the position report occupies one timeslot. Class-B (and Class-A) report their "static" information (name, callsign, dimensions, etc) once every six minutes. These static reports take two AIS timeslots. For a docked Class-B vessel, this adds up to just 0.66 timeslots per minute.

Compare that to a Class-A ship moving at 0-14 kts transmitting the dynamic report every 10 seconds, or every 3.33 seconds when turning. This is in addition to the 6-minute static reports. This translates to 6.33 or 18.33 timeslots per minute.

That means it takes 10-27 docked Class-B vessels to equal just one underway Class-A vessel. Class-B's are not overloading the system, at least not yet. And if they were, they would just back off on their transmit rate.

Again, turning off your Class-B might help a little. I almost always have mine off when in the slip, and I'm in an extremely non-busy area. But, this will not solve the fundamental problem.
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Old 18-05-2013, 15:07   #266
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by rwidman View Post
....
Why are people here trying to make a law when they have no authority to do so and no means of enforcing it? Turn it on, turn it off, it's an individual choice. There's no right or wrong way.
(my emphasis added for clarification of the following point)

All I've seen is a request for people to consider the implications of their actions.

Why do you choose to mis-characterise the intent of the thread in this way ?

[Note: this is a rhetorical question]
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Old 18-05-2013, 15:17   #267
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Re: Please turn your AIS off when docked/moored/anchored

According to the U.S. Coast Guard report, the #1 cause of boating accidents resulting in injuries is "Operator Inattention." The #4 cause is "Improper Lookout." So, whatever you do, and whatever instruments you use, pay attention to what is going on around you. Similarly, I wonder how many car accidents are now being caused by people watching the GPS unit?
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Old 18-05-2013, 16:26   #268
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Re: Please turn your AIS off when docked/moored/anchored

The only comment I have is one I've resisted making: it isn't called "The Commons".

It's called "The Tragedy of The Commons."

It isn't used to to demonstrate what should happen, (there are several versions of it, involving sheep, footpaths, snow & ice, and so on) it's used to demonstrate what does happen, and how humans always end up choosing what they perceive is best for them, even at the expense of others.

The italics I've added are important, and part of the point. The lesson goes on, but when one leaves the rails this early, the rest of it doesn't really matter.

When someone refers to The Tragedy of The Commons and indicates that it demonstrates some lesson about how we should all learn to stay off the grass (keep our sheep off the grass, clear the sidewalk of ice, etc.) I conclude that he or she does not understand the concept.

Applying the concept of The Tragedy of The Commons to AIS correctly yields this conclusion: people will walk (or cut, depending on version) across / let their sheep graze / fail to clear the sidewalk on the commons because they perceive that's what's best for them.

They will, therefore, either turn their AIS off or leave it on, depending on their perception of what's best for them.

This will result in footpaths worn across the commons, sheep grazing on it, and some AIS units off, others on.

That is the starting point for reasonable discussion, and I think it's exactly on point in a discussion about turning AIS off at the dock.

The Tragedy of The Commons does not tell us to keep our sheep off the commons.

It tells us that there will always be sheep on the commons.
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Old 18-05-2013, 16:36   #269
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Originally Posted by estarzinger View Post
just a purely factual post on two subjects tangential to my OP that have come up:


2. The actual IMO requirement for AIS operation is in fact NOT 7 x 24. It is "which entails the continuous operation of AIS and the accurate input and upkeep of AIS data fields during all times that the vessel is navigating."

Lets be precise here Evans , here's the relevant IMO resolution A9177(22)

"
21 AIS should always be in operation when ships are underway or at anchor. If the master believes that the continual operation of AIS might compromise the safety or security of his/her ship, the AIS may be switched off. This might be the case in sea areas where pirates and armed robbers are known to operate. Actions of this nature should always be recorded in the ship’s logbook together with the reason for doing so. The master should however restart the AIS as soon as the source of danger has disappeared. If the AIS is shut down, static data and voyage related information remains stored. Restart is done by switching on the power to the AIS unit. Ship’s own data will be transmitted after a two minute initialization period. In ports AIS operation should be in accordance with port requirements."


Hence there is no specific requirement that mentions ' navigating ' .

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Old 18-05-2013, 16:49   #270
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I tried to read all the posts but may have missed these observations:

1) I'm willing to bet that most of the docked AIS units are left on because of the web based AIS viewers. Owners from anywhere in the world can check if their boat has moved "for free". Is this a discourteous use of AIS? Probably so but it is debatable.

2) It is possible to have so many AIS units chattering that all available time slots are used up. This has thwarted attempts to provide a global monitoring system using AIS receivers on satellites. This is a fundamental flaw in the system in my view brought on by the desire (unfounded also in my view) to use low cost TDM GMSK as the air interface instead of something (e.g. CDMA or COFDM) that could handle a lot more squawking devices. Think WiFi for example. For this reason, I agree with Evans that AIS should be turned off when docked. It might help if AIS transmitters only tried to send data very infrequently (say once per hour) when stationary for some preset long time (like one hour). As AIS becomes more popular it will require some rethinking of the standard I believe.

3) Clearly the receive software needs to be improved a lot if it gives an alarm that you are in danger of collision with a stationary vessel even though it is obvious to the most casual watch keeper that there is no chance of a collision. I am tempted to blame this one on tort law issues but it could just be we need to let the software people work through these real world problems. Only time will tell if the situation improves or not. This thread will be seen by AIS software developers I am sure.

New technology will often require revisions of best practices and Evans request is not in vain. I believe he is right and I believe he along with other respected voices ought to speak up even if the great unwashed think it in vain. After all, necessity is the mother of invention. He is only pointing out a problem and some innovative person is probably thinking up solutions right now. If so then that would be the best outcome.
I think there is some confusing info here. AIS Class A is TDMA in particular SOTDMA. Class B is CSMA, and has as you pointed out is better at handling large numbers of devices but doesn't guarantee that every message will get through. AIS class B does throttle back transmissions significantly for vessels under 2knots.

As to point (1) the WWW interface to AIS is based on amateur stations , as the IMO has already asked member governments to restrict www feed from legitimate sources. I doubt anyone is relying on the www to detect vessel movement

"
2) It is possible to have so many AIS units chattering that all available time slots are used up. This has thwarted attempts to provide a global monitoring system using AIS receivers on satellites"

While it might be a desire or certain law enforcement bodies to use AIS in that way , it is not the purpose of AIS as agreed with the IMO . Satellite AIS monitoring is in place and reports suggest it is effective , but AIS is not designed to be a worldwide traffic Monitoring system and hence you're isnt is that relevant

Dave
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