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Old 19-05-2013, 09:40   #331
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Re: Please turn your AIS off when docked/moored/anchored

The way AIS class B is structured today, both technically (CSTDMA with 'noise sensing') and in the commonly available filtering/displays, "unnecessary signals" (We can discuss what that means later) will degrade the performance of the system.

I agree with Jedi that better filtering could reduce the burden on the second part and there is no downside to better filtering and I hope the mfg's place some emphasis on it. I also agree with Jedi that if I got a class A it would reduce the first problem . . . however I am concerned that having pleasure vessels switch to class A would make various problems worse for the large commercial vessels and I prefer to help them and not exacerbate their problems, So I personally would prefer to find a solution within class B.

If my cruising program was generally hanging around crowded places, I would in fact put a low speed filter into one of the vesper presets (probably the harbor one), so I could quickly toggle it on. But I choose to mostly cruise in less crowded places, and in those places I am more likely to encounter a 'slow speed' commercial vessel that is actually underway than a docked or moored class B. So for me, I believe, it is better not to have a low speed filter generally in place.

In this specific case, when leaving Block Island, heading past Newport, I could have put a low speed filter just in place for the next couple short legs (say thru the cape cod canal). And probably would have if I had known there were going to be so many docked units on in Newport. But I had not anticipated that so instead I essentially just turned all the alarms off when I encountered the big bunch at the channel mouth.

One thing that puzzled me is that while there were a lot of units on in Newport, there were NOT any on at East Passage (a huge yacht basin just further up the channel). So I did take a little time yesterday ashore and called a few folks to try to understand that. What I was told was that in Newport there is a major installer who installs black box AIS units with an inline fuse wired to a master breaker without any separate on/off switch, while in east passage there are two installers who both wire the black boxes either to its own breaker or add an off/off switch to the power lead. So, if what those folks told me is correct, this particular circumstance is an installation issue and not an explicit owners decision whether to turn the units on or not. These owners are not 'choosing' to turn their units on, and don't need it on, and so these at least qualify in my mind as an 'unnecessary load' on the AIS system. So, 'my problem' would seem to be solved if it was generally agreed that AIS black boxes should be installed with some sort of on/off switches.
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Old 19-05-2013, 10:01   #332
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Re: Please turn your AIS off when docked/moored/anchored

My guess for this difference between East Passage and Newport would be that Newport Shipyard is the superyacht marina in the area, and those folks are more likely to have AIS on, though I would think it would be Class A. I really can't imagine many owners of ordinary-sized craft leave their electronics powered up all the time--I personally don't know of anybody who does that, but apparently they do.

By the way, if you are ever in Newport take a wander around Newport Shipyard if you don't mind a case of wallet envy.
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Old 19-05-2013, 10:04   #333
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In this case at some point the system is likely to be overwhelmed to the point where class B's are almost useless for navigation safety near any major port. Class A's have the capacity to deal with overload, I am not sure class B's do? filtering will be a side issue.
Yes that is the case

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Old 19-05-2013, 10:06   #334
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Re: Please turn your AIS off when docked/moored/anchored

Here's another AIS position-error story, that I heard from my VTS friend:

One day they were watching their screens, and noticed about a dozen ships drifting away as a fleet, at least as indicated by the AIS icons. The radar blips were still in their original spots, but the AIS icons were all drifting at the same course and speed. They ended up a mile or so from their original positions. Not all ships were "drifting", but a lot were.

Obviously the ships weren't drifting, but they were all using a GPS receiver that was using a DGPS (differential GPS) satellite which had been taken out of service. The bad data from that satellite was giving their AIS transponder bad position data.

Within a few minutes, all the ships snapped back to their proper positions.

Moral? Don't depend on any single method of navigation.
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Old 19-05-2013, 10:30   #335
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Re: Please turn your AIS off when docked/moored/anchored

I would likely have had to figure out the hard way to have filter presets setup for my cruising grounds, so it's helpful to hear other's experience. Definitely would be using eyeball nav way more in busy harbors, but removing slow-moving vessels from the pre-set harbor alarm would help. Singlehanding, I would want to use an alarm, for that 40 seconds I run below to handle/check something, or after dark, or whatever. Also to make hailing ships easier, either by DSC or just having ships name. And good point Paul re: reliance on the system. Keeping channel 13/16 on and eyes peeled is the best, although 4G radar and AIS outperform these in low visibility conditions.

My VHF/AIS combo does not have very sophisticated filtering, and I'm a little out of the loop on some of the info presented, but I have no experience with Open CPN or commercial Nav software and I'm not sure how a more sohositicated program would fit my situation. It jus't isn't that practical for me at an exposed helm running the boat by myself so I'll be limited to what the marine electronics industry can provide. Luckily I don't have the money now and by the time I do, there may be some improvements. I'm not convinced that current settings, when customized, wouldn't meet my needs though.
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Old 19-05-2013, 10:48   #336
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by colemj View Post
But Boatman, as a previous poster pointed out on this thread, all of the experienced cruisers are agreeing with Evans and the ones without much experience are the ones that have been disagreeing. So you do not have enough experience.

Mark
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Old 19-05-2013, 10:56   #337
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Re: Please turn your AIS off when docked/moored/anchored

Quote:
Originally Posted by estarzinger View Post
The way AIS class B is structured today, both technically (CSTDMA with 'noise sensing') and in the commonly available filtering/displays, "unnecessary signals" (We can discuss what that means later) will degrade the performance of the system.

I agree with Jedi that better filtering could reduce the burden on the second part and there is no downside to better filtering and I hope the mfg's place some emphasis on it. I also agree with Jedi that if I got a class A it would reduce the first problem . . . however I am concerned that having pleasure vessels switch to class A would make various problems worse for the large commercial vessels and I prefer to help them and not exacerbate their problems, So I personally would prefer to find a solution within class B.

If my cruising program was generally hanging around crowded places, I would in fact put a low speed filter into one of the vesper presets (probably the harbor one), so I could quickly toggle it on. But I choose to mostly cruise in less crowded places, and in those places I am more likely to encounter a 'slow speed' commercial vessel that is actually underway than a docked or moored class B. So for me, I believe, it is better not to have a low speed filter generally in place.

In this specific case, when leaving Block Island, heading past Newport, I could have put a low speed filter just in place for the next couple short legs (say thru the cape cod canal). And probably would have if I had known there were going to be so many docked units on in Newport. But I had not anticipated that so instead I essentially just turned all the alarms off when I encountered the big bunch at the channel mouth.

One thing that puzzled me is that while there were a lot of units on in Newport, there were NOT any on at East Passage (a huge yacht basin just further up the channel). So I did take a little time yesterday ashore and called a few folks to try to understand that. What I was told was that in Newport there is a major installer who installs black box AIS units with an inline fuse wired to a master breaker without any separate on/off switch, while in east passage there are two installers who both wire the black boxes either to its own breaker or add an off/off switch to the power lead. So, if what those folks told me is correct, this particular circumstance is an installation issue and not an explicit owners decision whether to turn the units on or not. These owners are not 'choosing' to turn their units on, and don't need it on, and so these at least qualify in my mind as an 'unnecessary load' on the AIS system. So, 'my problem' would seem to be solved if it was generally agreed that AIS black boxes should be installed with some sort of on/off switches.
A couple of questions and comments.

Is it legal to install class A on recreational boats? I was under the impression this was not legal, at least in the recent past.

Evans, where exactly were you in/around Newport? You mentioned leaving BI for the CC canal, but I don't see how Newport comes into that. If your alarms were going off for vessels well over a mile away from you (the BB channel to the canal is 6 miles from Newport Harbor), then I really think that should not have been an issue.

I do think it is an owner's decision if they do not understand what/why an installer did on their boat. It was their decision to install it and their responsibility to know how it operates. But yes, I understand this is Newport after all...

Even if all were switched, your problem would only be solved if they all switched them off (and we would come full circle here).

As an aside, I don't understand the logic of an installer in wiring to a main breaker. I understand leaving the main breaker on when off the boat, but would expect everything powered to be on their own switches (bilge pumps and the like excepted).

Mark
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Old 19-05-2013, 11:09   #338
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pirate Re: Please turn your AIS off when docked/moored/anchored

This ones fun... not counting either side and behind...
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Old 19-05-2013, 11:17   #339
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Re: Please turn your AIS off when docked/moored/anchored

Much ado about nothing.

If a boat isn't moving (or moving very slowly) and you hit it, it's your fault, end of story.
If it's a fishing boat pulling pots and takes off, it will show up again as a critical target.
In a busy harbor boats are going here, there and everywhere with frequent often random turns at high speed. No system will ever be able to predict when uncle buck is going to make a hard right across your bow. Best to scan the screen for a few seconds periodically and make an assesment of threats.

As there is no rule against running it in a slip and people have shown reasonable uses (even if you don't personally agree with them), it's not a moral issue.
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Old 19-05-2013, 11:25   #340
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by colemj View Post

Is it legal to install class A on recreational boats?

Yes, it is.

Evans, where exactly were you in/around Newport? You mentioned leaving BI for the CC canal, but I don't see how Newport comes into that.

I ran from Block up by Newport, to a friend's mooring outside Bristol, to have dinner and do some laundry. It was at the coal power plant past Bristol where the 'greenpeace' environmental vessel was blocking the channel to try and prevent coal from being unloaded.

By the way, you and others have commented on ais not that useful while actually in the close confines of a harbor (and have suggested much tighter cpa filters for a 'harbor'). I agree. But I think perhaps Vesper's definition of "harbor" is more like SF bay or Auckland harbor or Sandy hook, or the entire Chesapeake bay. In which case the AIS is useful in that somewhat bigger environment.

I do think it is an owner's decision if they do not understand what/why an installer did on their boat. It was their decision to install it and their responsibility to know how it operates. But yes, I understand this is Newport after all...

Agree with all that . . . but most/many owners would accept a pro install without any questions.

Even if all were switched, your problem would only be solved if they all switched them off (and we would come full circle here).

Agreed, but it seemed empirically like in east passage, when they did have switches, they did in fact switch them off. None of that is statistical and is based on hear-say from my phone conversations, so I don't know if its the true or full explanation.

I also know that many 'semi-pro' captains have been trained simply never to turn electronics off. I occasionally baby sit superyachts when the captains go on vacation, and that has usually been the standing order to me. The reason is usually that there is a pc somewhere in the system that does not reboot reliability to the exact configuration the captain likes, so he just wants it left on. These boats typically have IMO/class A systems, which is why I knew what the class B filter set-up was.

As an aside, I don't understand the logic of an installer in wiring to a main breaker. I understand leaving the main breaker on when off the boat, but would expect everything powered to be on their own switches (bilge pumps and the like excepted).

I don't know, but easy and quick and lazy come to mind as reasons not to install a switch or extra breaker.
..........
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Old 19-05-2013, 11:43   #341
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Re: Please turn your AIS off when docked/moored/anchored

Thanks for the info Evans.

But in all fairness, that coal plant, and the position of the blocked vessel was 10-12 miles away from Newport Harbor, where the docked boats you complained about interfering with your alarms and navigation were located. I don't see how they even triggered your alarms, unless the criteria was extremely loose.

For accuracy, I do think AIS is useful in harbors and other close confines. I don't think audible alarms are useful there. And in these environments I have no problems at all incorporating AIS data into my navigational situation regardless of the number of boats who have no reason to have it on.

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Old 19-05-2013, 12:32   #342
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Re: Please turn your AIS off when docked/moored/anchored

I can imagine in the future, the government will require all vessels to have AIS on all the time, then some can complain about people who don't follow rules and turn them off....
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Old 19-05-2013, 12:52   #343
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Re: Please turn your AIS off when docked/moored/anchored

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But in all fairness, that coal plant, and the position of the blocked vessel was 10-12 miles away from Newport Harbor, where the docked boats you complained about interfering with your alarms and navigation were located.
Mark, in fairness, I find your post a bit frustrating.

Do you really think I should have set one low speed filter when approaching Newport and then removed it when I was by?

I don't know anyone who is continuously adjusting their AIS filters as they are sailing - do you?

If not, then I in theory had a choice: either I do not have a low speed filter on and I have the 'Newport problem' or I do have the low speed filter on and I don't get an alarm for the two ships near stopped in the channel an hour later. I chose the first option. I think it was the best choice for the way I operate my vessel and they way it is equipped.

If your answer is yet again that you don't really care for alarms, then we can yet again agree that you don't but I do. If your answer is yet again that you are comfortable with much shorter range cpa alarms than I am, then we can yet again agree you operate differently than I do. I have no problem with that. I operate in my way and you can in your way . . . when neither of us are effecting the other. Why do you continue to seem to want me to operate exactly like you do?

And really none of this has anything to do with my OP - which was a simple polite request that docked and moored boats consider turning off their class B's (unless they have a specific safety reason for having them on), because by leaving them on they are possibly degrading a shared anti-collision system. It seems that you and most others here (except I think Jedi) have agreed that makes sense.
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Old 19-05-2013, 13:00   #344
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Re: Please turn your AIS off when docked/moored/anchored

Yes but you called everybody who does not act like you, names. By this point I think almost eveyone understands your position and vise versa.
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Old 19-05-2013, 13:09   #345
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Re: Please turn your AIS off when docked/moored/anchored

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Yes but you called everybody who does not act like you, names.
No I do and DID not.

I am perfectly happy with people operating differently than I do. I am perfectly with Jedi running a Class A unit. I am perfectly happy if Mark does not use alarms much and wants to use very tight CPA filters. I have called none of them 'names' for that.

What I said, way back in the thread, was that if someone intentionally and knowingly degrades a shared safety system with unnecessary signals . . . then I think less of them.

Do you really and seriously disagree with that? Do you really feel terrific about someone who would intentionally and knowingly degrade a shared safety system?
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