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Old 18-05-2013, 09:23   #226
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by colemj View Post
Well, you just restated what several of us have been saying.

The OP's issue was navigating in a harbor with dozens of vessels in close quarters.

Operator adjustment to this situation was the point some of us were making.

Whether the system itself can handle it has had some debate, with several providing data suggesting that there is no real problem. I can't believe class B was designed from the start without thought to the possibility that more than a few boats would be using it at any given time.

But perhaps it was. In that case, with countries either mandating it or considering mandating it, I suspect that the system will be adjusted to accommodate.

Adjusting the operator will still be a requirement, though.

Mark
Yes, I appreciated those arguments when they were made, and I think they are valid. I still, personally, come out more on the side of Evans and Nigel -- if my transmissions from a dock or mooring are causing irritation, I really don't have a problem switching it off. But the discussion has gone way beyond that, and I find it quite interesting.

I don't have alarms configured on my AIS when I am in harbors and when I am sailing coastwise, so I don't have these problems myself, but others use their systems differently, and commercial mariners may not even have any choice, so I think it's important to consider their point of view.

I think a lot of the issue is the result of AIS being designed for situations which many of us don't encounter very often. I don't have any problem with collision avoidance in close quarters -- eyeballs, common sense, and following the Colregs has always dealt with that, maybe plus radar if there is any visibility problem, and I would never hope that AIS or any other gadget could help. The real challenge of collision avoidance is in open water, especially crossing shipping lanes, where your eyeballs aren't much good until it's too late, and where you really need to understand whether that ship is going to cross ahead or behind, and it might be a life or death question. In these situations, the problem which is the subject of this thread does not exist, and AIS is the supreme tool.

In my opinion, AIS was never intended to do anything useful in a busy harbor, and the designers probably never considered these problems which we are discussing. Probably -- as has been said -- we need much better filtering, and maybe we need to just shut it down in such cases.
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Old 18-05-2013, 09:30   #227
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by Kettlewell View Post
The point I am making is that if you combine the marina photo and your photos you have a worse situation than you have without all the boats transmitting in the marina. It isn't about entering the marina, it is about passing near to the marina while at the same time dealing with actual traffic you have to worry about out in the channel. There are numerous places in the world with lots of boats in marinas in a small area. I have read that there are 40,000 resident yachts in Ft. Lauderdale, and those would all be within a few miles of the inlet. OK, so you filter out the ones that aren't moving, but then that eliminates all the cruise ships hovering waiting to enter the port, or the Pilot Boat, or the marine patrol, or the boats just idling for a moment.

Maybe the answer is just an "in port function" on AIS that is triggered automatically once your boat hasn't moved for say an hour or something.
If one meteor hitting the earth destroys all life, is it "worse" if 100 of them hit?

You must understand: there is no "worse" situation. Once the target density exceeds a rather small number, the OP's "problem" is triggered. A solution to that problem will deal with your so-called "worse" situation.

So, no. Having 100 in use targets AND 100 not in use targets is not worse than only having 100 in use targets - it is the same thing.

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Old 18-05-2013, 09:36   #228
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Re: Please turn your AIS off when docked/moored/anchored

Several posters keep reiterating false information. The OP was not in the harbor, he was passing near the harbor in a well-marked and busy shipping channel. He was not talking about trying to navigate around a harbor. However, numerous AIS transmitting boats within the harbor, apparently at docks and on moorings, were causing proximity and other alarms to go off because the harbor is so close to the channel. Filtering is all well and good, but in that situation you can't filter for proximity, you can't filter for speed over the ground because there are numerous craft, including a large commercial one, that were just hovering waiting to do something. If you were in the fog you might want to know that a coal carrier is temporarily stopped across the entire width of the channel up ahead, but there is no navigational reason you need to know that someone's Wet Dreams is safely tied up to a mooring in Newport.
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Old 18-05-2013, 09:36   #229
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by Dockhead View Post
Yes, I appreciated those arguments when they were made, and I think they are valid. I still, personally, come out more on the side of Evans and Nigel -- if my transmissions from a dock or mooring are causing irritation, I really don't have a problem switching it off.

As I have stated numerous times, I agree with this, see few good reasons to still be transmitting, and would turn mine off if I had a transponder.

BUT! That is not the point, or even the OP's stated problem. That problem was too many alarms confusing or distracting him. He will have the same problem when all docked boats are silent and all boats on the water are transmitting. The solutions and tactics that would solve his present problems will be the same ones that will solve his future problems. He does not appear to see that far ahead.


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In my opinion, AIS was never intended to do anything useful in a busy harbor, and the designers probably never considered these problems which we are discussing.
On the contrary, I suspect that AIS was always intended for harbor control and tracking of commercial ships - similar to aircraft transponders. I could be wrong and will stand corrected if this was not the case.

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Old 18-05-2013, 09:51   #230
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Re: Please turn your AIS off when docked/moored/anchored

Quote:
Originally Posted by Kettlewell View Post
Several posters keep reiterating false information. The OP was not in the harbor, he was passing near the harbor in a well-marked and busy shipping channel. He was not talking about trying to navigate around a harbor. However, numerous AIS transmitting boats within the harbor, apparently at docks and on moorings, were causing proximity and other alarms to go off because the harbor is so close to the channel. Filtering is all well and good, but in that situation you can't filter for proximity, you can't filter for speed over the ground because there are numerous craft, including a large commercial one, that were just hovering waiting to do something. If you were in the fog you might want to know that a coal carrier is temporarily stopped across the entire width of the channel up ahead, but there is no navigational reason you need to know that someone's Wet Dreams is safely tied up to a mooring in Newport.
That is splitting a fine semantic hair. That harbor IS the shipping channel. Marinas and mooring fields set outside of, and close to, it but when you are in the shipping channel, you are in the harbor. I don't know of anyone who, upon rounding the point doesn't think they are entering "Newport Harbor", even though that isn't properly accurate.

For those unfamiliar, the Newport harbor docks are 1.2nm away from the main shipping channel at their closest point. The mooring fields are 1nm away. Anchoring is allowed in many places, and can be close to the shipping channel.

The shipping channel is also fairly straight, with a loose dog-leg, but no bends that prevent seeing around.

I suspect the described problems of the OP was because he actually WAS in the harbor properly and not in the main shipping channel. Only he could tell us.

Even given this situation, having the alarms activated was not the proper tactic. If all docked and moored boats stopped transmitting, the OP will still encounter his "problem" in different areas in the future. In the fog, one's tactics should be far different that relying on AIS alarms, and I don't think even the OP would be making this particular case in that situation.

And one CAN filter for his particular situation. We do it all the time.

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Old 18-05-2013, 09:51   #231
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Re: Please turn your AIS off when docked/moored/anchored

The perspective on the stage of development of the technology adds a lot to the discussion. Good walk down the Internet memory lane, too

When my AIS (receive only) system went down this summer sailing down the Chesapeake through the night, I was really challenged by the commercial traffic heading N. I was heading S, winds 25-30 knots and gusting higher, having a great time surfing, and realizing that crealocks do in fact handle very nicely in these surfing conditions - it's not just marketing!

Piloting by itself was easy enough with paper charts and lots of lights marking the channel, but no matter how hard I tried, boats started to sneak up on me. I issued a securite on 13 (1W) every time I thought I saw one coming, and had several conversations. My VHF was the only working electronics, even my two handheld GPS units failed!

A couple of the commercial operators asked me if I had AIS, or why didn't I have AIS, as I confirmed they had a visual, or a return on me. It does seem that they appreciate being able to see pesky little sailboats out in the dark, and AIS is much richer info than radar for collision avoidance. I'm saving up for one now -- it makes everyones life easier out on the water when used properly and might save my a**.

Sounds like vesper is the way to go? Is an arch a good place for that VHF antenna? Could prolly start a new thread on this but likely there are others and I'm happy enough to try to redirect the conversation a little. Hopefully I can get NMEA talking to my older 5" Garmin, but no luck yet with the Standard Horizon VHF/AIS talking to it...
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Old 18-05-2013, 09:58   #232
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Re: Please turn your AIS off when docked/moored/anchored

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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.
Not exactly. First of all, Class-B units will never overload the system. They automatically back off as more Class-A units come on line.

And the problem with satellite monitoring is that the satellite is potentially receiving multiple AIS "domains" at the same time. Each domain may be operating perfectly well, and at moderate capacity, but when you try to receive signals from two or more domains you will see multiple signals in the same timeslot interfering with each other.

This is similar to the situation when you are listening to FM or AM radio in your car, and you are in a fringe area -- competing signals on the same frequency will interfere with each other.

The reason I mention this is to point out that the problem is *not* that Class-B units are overcrowding the AIS system. They're not. The problem is that our display and alarm equipment is not designed (yet) to present close-quarters AIS targets in a useful way. This will happen in time, but until then we've got to work with what we have. I agree that there's no critical reason to keep my AIS transponder active when I am in my slip. But I also think the OP's problem is not limited to docked boats, and turning off the docked transponders will not solve it. It might make it a little less annoying though. The real solution will come from better design of the monitoring gear.
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Old 18-05-2013, 10:07   #233
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Re: Please turn your AIS off when docked/moored/anchored

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Not exactly. First of all, Class-B units will never overload the system. They automatically back off as more Class-A units come on line.

....

The reason I mention this is to point out that the problem is *not* that Class-B units are overcrowding the AIS system. They're not.
The OP states exactly the opposite.

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Old 18-05-2013, 10:09   #234
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Re: Please turn your AIS off when docked/moored/anchored

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A perceptive comment.

It does seem to me that the problem is fundamentally in the system, and not in the way people use it.

The system should not be overwhelmed by targets, and should not require people to do particular things to prevent interference.

Sounds to me like there are too few time slots and too little processing power in the system, and not nearly sophisticated enough filtering.
The part I bolded is half-right. Time slots and processing power are not the problem. The AIS system is not overloaded, and there are generally plenty of timeslots to go around. The OP's problem had absolutely nothing to do with overloaded timeslots.

The system (whichever system we want to talk about) has plenty of processing power. That's not an issue.

Sophisticated filtering -- YES! That's what we need, and it isn't there yet.

Funny, I haven't heard anyone asking me to pull down my radar reflector when I'm in the slip. Perhaps I should put stealth technology on my boat? Oh, it's not a problem? Then why is my little AIS target icon a problem?
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Old 18-05-2013, 10:12   #235
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Re: Please turn your AIS off when docked/moored/anchored

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Gee, is it hard to get on Wikipedia?
Nope, but I checked and you and I both were not there. I don't always agree with evans, but his opinion is based on expereince and not fantasy, so its always worth listening to, and then sometimes agreeing and sometimes disagreeing.

On this issue I agree with Evans, cept for the at anchor bit and even then only when it isnt a recognised anchor field. Due to the explosion in transponders around here, I turn all my alarms off when sailing in the bay, and sometimes when sailing up the coast.
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Old 18-05-2013, 10:12   #236
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Re: Please turn your AIS off when docked/moored/anchored

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Then why is my little AIS target icon a problem?
Because it is causing alarms to go off on other's AIS units. Most people turn off their radar alarms when entering harbor areas.

Hey! I just had an idea....

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Old 18-05-2013, 10:17   #237
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Re: Please turn your AIS off when docked/moored/anchored

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On this issue I agree with Evans, cept for the at anchor bit and even then only when it isnt a recognised anchor field.
I am now tilting at windmills trying to keep this debate centered on the real issue.

Do you agree that the OP's "problem" goes away once and for all when every docked and moored (but not anchored, in your case, which differs for him) turn off their transponders?

Or are you simply reacting to the gut emotional level of "that seems like the right thing to do, shame on them", and going off into a side show issue?

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Old 18-05-2013, 10:17   #238
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Re: Please turn your AIS off when docked/moored/anchored

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The OP states exactly the opposite.

Mark
If you are referring to that "commons" argument, I suppose that depends on how you define "commons". If the OP thinks that those Class-B transponders were overloading the AIS timeslots, I can state with virtual certanty that this was not the case.

They may have been overloading his alarm "system", but that's not at all the same thing. That, I think, is the real crux of the problem.
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Old 18-05-2013, 10:26   #239
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Re: Please turn your AIS off when docked/moored/anchored

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- just appeals to the "common good" and "courtesy", etc.
I'm still wondering why this approach seems to be such an issue. What's wrong with courtesy?

It appears that the contributions suggesting improved filtering algorithms has great merit.

Also, many of us sail in different venues. Here, on San Francisco Bay, there is a great deal of commercial traffic. One of the rarely mentioned things about sailing here is the courtesy (there's that word again!) of the skippers of ferry vessels, which almost always stay clear of sailing vessels. As far as I know, this may be limited to the SF Bay alone, since I've read that New York Harbor, for example, requires sailboats to keep out of the way of almost everything else and that the Staten Island ferry isn't going to alter course to miss you, as the Vallejo and other ferries routinely do here.

The only things that we have to get out of the way for here are the large containerships and other large vessels in the shipping channels. We have VTS on Ch 14 that tells you where they all are in The Bay, and VTS Ch12 for coastal traffic. It's not so hard, even without AIS, to safely stay out of their way.

We may be unique in this regard. Any input from other venues with routinely heavy commercial traffic?
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Old 18-05-2013, 10:33   #240
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Re: Please turn your AIS off when docked/moored/anchored

The OP stated: "I have explained why I think docked class B units should turn off their systems - simply because they are degrading a shared collision avoidance system"

I do not know enough to make any judgement on its accuracy (or yours), which is why I keep that point active in this thread. I would like to understand it better.

The OP also stated: "I was sailing by NY city and there was so much AIS noise that my unit could not find a transmission slot for about half of its scheduled broadcasts."

He didn't state whether that was because of all the commercial class A traffic or all the scoundrels at the docks with their class B broadcasting. He also didn't state whether his receiving capabilities were degraded, which seem more important to immediate navigation than transmitting to me.

If there is class B degradation in the sense of slower transmission rates, I can deal with a 5kt sailboat only giving me updates every few minutes.

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