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Old 21-01-2017, 15:52   #211
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Re: Class B AIS waste of money

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I rest my case.



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Old 21-01-2017, 16:18   #212
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Re: Class B AIS waste of money

The wide presence of AIS on many leisure boats is determining some unexpected bias in the way professional operators may use and rely on that information.
That is evident from the many contributions here.

Now, keeping a whole hearted confidence in the instrument without realizing the downfalls in practical terms may generate a false sense of security, and is dangerous. Personal opinion.

I may agree that the pros overcome the cons.

But, having a pinky view on this issue is simplistic. Anyone is entitled to think different and try to apply his/her own 'logic'.
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Old 21-01-2017, 16:32   #213
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Re: Class B AIS waste of money

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Originally Posted by TheThunderbird View Post
The wide presence of AIS on many leisure boats is determining some unexpected bias in the way professional operators may use and rely on that information.
That is evident from the many contributions here.

Now, keeping a whole hearted confidence in the instrument without realizing the downfalls in practical terms may generate a false sense of security, and is dangerous. Personal opinion.

I may agree that the pros overcome the cons.

But, having a pinky view on this issue is simplistic. Anyone is entitled to think different and try to apply his/her own 'logic'.
Sounds like an almost complete backdown on your original position.

Glad to see logic prevail.
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Old 21-01-2017, 16:34   #214
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Re: Class B AIS waste of money

Class B AIS waste of money? maybe.. SVB24 Germany is now selling the new class B SOTDMA (Self Organizing TDMA) AIS Transponder from AMEC for Euro 999,95 https://www.svb24.com/en/amec-b600-a...ansponder.html

Some background information on class B SOTDMA (Self Organizing TDMA) AIS Transponders from the PANBO website. Panbo: The Marine Electronics Hub: SOTDMA Class B AIS, the "new" middle way?
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Old 22-01-2017, 00:35   #215
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Re: Class B AIS waste of money

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. . . Now, keeping a whole hearted confidence in the instrument without realizing the downfalls in practical terms may generate a false sense of security, and is dangerous. Personal opinion. .
I agree.

But this applies to every nav system -- GPS, radar, even the hand bearing compass

But I don't think anyone would ever say that it's better to just not know where you are at all, in order to avoid the dangers of overconfidence, which might come from having GPS or even a hand bearing compass.

Or a chart. Maybe it's better to throw away our charts, so that we don't become overconfident, about knowing what's out there?

Likewise -- I don't think you can say that it's better for other vessels to simply not know you're out there, just to avoid the danger of overconfidence, which might come from knowing you are broadcasting AIS data.

There are a lot better ways to fight overconfidence!

Not being seen, just like not knowing where you are, is simply dangerous. Anything which adds to being seen, just like anything which adds to knowing where you are, is a good thing.
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Old 22-01-2017, 02:07   #216
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Re: Class B AIS waste of money

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Class B ? 30 second update? Under the bow? AIS would be as much use as tits on a bull in that situation.

30 seconds is a very long time on the bridge of a ship in pilotage waters.....
If I have an AIS contact that I can't immediately see, I make a point of trying to track it down. While that might not work in busy waters I'd say it still helps to know it is there.

On the wider subject, Practical Boat Owner did a piece on this recently "Do big ships filter out Class B transmissions". They spoke to several deck officers who all said they would not not filter out class B targets.

A couple further commented that some boats are 'self filtering' in that they only appear on AIS at around 5 miles or so.

Another interesting comment specifically mentioned the difficulty of spotting boats on radar that don't have reflectors, and how AIS helps with those.
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Old 22-01-2017, 02:33   #217
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Re: Class B AIS waste of money

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On the wider subject, Practical Boat Owner did a piece on this recently "Do big ships filter out Class B transmissions". They spoke to several deck officers who all said they would not not filter out class B targets.
They won't filter them personally because they don't know how to, they have to get an Able Seaman (Engineering) to do it for them - just ask the OP
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Old 22-01-2017, 05:55   #218
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Re: Class B AIS waste of money

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They won't filter them personally because they don't know how to, they have to get an Able Seaman (Engineering) to do it for them - just ask the OP
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Old 22-01-2017, 06:48   #219
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Re: Class B AIS waste of money

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Practical Boat Owner did a piece on this recently "Do big ships filter out Class B transmissions". They spoke to several deck officers who all said they would not not filter out class B targets.
I could just imagine the legal reprocussions if a ship's captain or bridge office filtered out Class B and then ran over a boat killing 5 children and their parents.


I doubt there are very many utterly stupid ship's officers at sea... Even though some internet forums like GCaptain may think contrary.
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Old 22-01-2017, 06:50   #220
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Re: Class B AIS waste of money

They sure as hell avoid me.

3 ship's diverting at once in Florida Straits at 2am. No VHF cons needed.



*Interesting note for people who pretend there's a rule of tonnage. I was the Stand On Vessle in both sets of rules, sailing and motor, but if I had changed course to starboard to clear room for the ship giving me the alarm I would have run dead into the one behind it who was just starting to divert his course. If I had then the VHF would have lit up with agitated captains. (The red range ring is 10nm)
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Old 22-01-2017, 07:03   #221
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Re: Class B AIS waste of money

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*Interesting note for people who pretend there's a rule of tonnage. I was the Stand On Vessle in both sets of rules, sailing and motor, but if I had changed course to starboard to clear room for the ship giving me the alarm I would have run dead into the one behind it who was just starting to divert his course. If I had then the VHF would have lit up with agitated captains.
Rule of tonnage only applies if both ships see each other. If they don't than who has the tonnage on their side? In a harbor or close quarters, yes stay away from the big boys, At sea at 10 miles range apply the colregs. If you have AIS or not, call them.
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Old 22-01-2017, 07:04   #222
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Re: Class B AIS waste of money

My experience from using AIS (cl A at work, and cl B on my boat) is that it is very useful - when it works! Cl B can very often be far longer than 30 secs between updates - several minutes IME. Cl A often seems to have trouble getting or keeping tracks from other cl A ships - I don't know if this is caused by wooding of the antennas, interference or whatever? I would not trust AIS for anti-collision exclusively. When coupled with radar and visual bearings, it can be a very handy tool.
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Old 22-01-2017, 07:26   #223
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Re: Class B AIS waste of money

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They sure as hell avoid me.

3 ship's diverting at once in Florida Straits at 2am. No VHF cons needed.



*Interesting note for people who pretend there's a rule of tonnage. I was the Stand On Vessle in both sets of rules, sailing and motor, but if I had changed course to starboard to clear room for the ship giving me the alarm I would have run dead into the one behind it who was just starting to divert his course. If I had then the VHF would have lit up with agitated captains. (The red range ring is 10nm)

See what happens when you actually go to sea and use this stuff, and follow the COLRESs, and do what you are supposed to do and expected to do? It's very different from what a lot of people sitting behind a keyboard imagine.
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Old 22-01-2017, 07:52   #224
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Re: Class B AIS waste of money

Appears to be an argument between real experience and internet theory.

We have over 6 years, 30,000+nm and hundreds of big ship interactions using Class B AIS. As Mark says, an absolutely invaluable safety tool. Big ships change course to avoid you, call on the VHF to reassure you, answer when you call and increase the CPA when requested.

We have never thought that they had us filtered out...sometimes it takes a few minutes for them to confirm that they are tracking you but we call them when the CPA is out at 20-30 minutes so there is lots of time to work things out.

We transmit and receive from a 76 ft mast so we pick them up at over 20nm.

The only ships to attempt to ignore our calls were US warships in International Waters who do not transmit on AIS. I can understand their caution in the Gulf of Aden but between the Jacksonville and the Caribbean my wife announced her intentions to 'stand on' and they changed course!
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Old 22-01-2017, 11:02   #225
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Re: Class B AIS waste of money

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My experience from using AIS (cl A at work, and cl B on my boat) is that it is very useful - when it works! Cl B can very often be far longer than 30 secs between updates - several minutes IME. Cl A often seems to have trouble getting or keeping tracks from other cl A ships - I don't know if this is caused by wooding of the antennas, interference or whatever? I would not trust AIS for anti-collision exclusively. When coupled with radar and visual bearings, it can be a very handy tool.
The new class B SOTDMA Transponders sends at 0Kn vessel speed 1x every 3 minutes which increases to 1x every 2 seconds at vessel speeds > 25 knots...
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