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Old 20-05-2013, 13:13   #436
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Re: Please turn your AIS off when docked/moored/anchored

I think at this stage all you can summarise is that the likelyhood of Class B <2Kts transmissions have virtually no demand on the available bandwidth and that they , unless in huge numbers, have any effect on blocking other class B transmissions. Hence while the 'docked' lesiure yachts might cause a screen clutter issue, ( and thats really filtering) , its not an impediment to the AIS system working.

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Old 20-05-2013, 13:22   #437
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Re: Please turn your AIS off when docked/moored/anchored

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Originally Posted by colemj View Post
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Originally Posted by Paul Elliott Navstat anchored or moored, SOG > 3 kts -- 10 seconds

How does this possible? Or is it just meant to account for boats that have an incorrect status entered?



That's my take; in case of incorrect navstat. Or dragging anchor, I suppose.
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Old 20-05-2013, 13:25   #438
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Re: Please turn your AIS off when docked/moored/anchored

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Quote:
Originally Posted by Paul Elliott
Navstat anchored or moored, SOG > 3 kts -- 10 seconds
How does this possible? Or is it just meant to account for boats that have an incorrect status entered?

Mark
That's only because there's no status category in AIS for dragging anchor!
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Old 20-05-2013, 13:26   #439
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Re: Please turn your AIS off when docked/moored/anchored

As for filtering, if someone wanted to set their alarm filter to exclude Class-B with speed <= 0.1 kts, that wouldn't get me too upset. I would still personally want to see them displayed, just not in flashing red, or whatever your alarm-status icons look like.
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Old 20-05-2013, 13:28   #440
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Re: Please turn your AIS off when docked/moored/anchored

Waiting for this thread to retire! Mauritz
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Old 20-05-2013, 13:29   #441
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Re: Please turn your AIS off when docked/moored/anchored

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Waiting for this thread to retire! Mauritz
bump , why very interesting discussion on AIS protocols etc, v interesting.
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Old 20-05-2013, 13:31   #442
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Re: Please turn your AIS off when docked/moored/anchored

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Waiting for this thread to retire! Mauritz
Why would you care? Apparently some of us enjoy the topic, and perhaps even the digressions. If it bugs you, see the title "Re: Please turn your AIS off when docked/moored/anchored"? Don't click on that.
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Old 20-05-2013, 13:31   #443
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Re: Please turn your AIS off when docked/moored/anchored

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AIS is a technical protocol for collision avoidance, there is no "commons" argument.
As far as USA law is concerned, you are 100% wrong. Since the dawn of radio, USA airwaves have been considered a public commons, subject to regulation in terms of frequency use, transmission power, acceptable types of use, et cetera. That's how it's possible to come up with regulations excluding commercial traffic on certain high frequencies, restricting other frequencies to marine-only use, prohibiting pornography on broadcast TV, et cetera.

I'm guessing we all agree that Joe Schmoe ought not be using Marine VHF 16 to chat about whether "Anybody Else Out There" is catching any fish. But this may largely be a result of regulations restricting that channel to hailing and distress. At present, however, there are no regulations restricting the use of AIS frequencies by boats sitting fat and pretty in the dock. Evans has suggested that boats who do so, regardless of the fact it's not illegal, are abusing the commons.

You can howl all you want about how misguided you find estarzinger's arguments to be, but as long as AIS transmitters use public airways, a commons is involved.

(I find it fascinating, parenthetically, how a few of you keep trying to re-frame the argument. Evans has stated that he sees this as being about community, specifically the cruising community, and how we use a commons. Why is that so difficult to accept?)
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Old 20-05-2013, 13:45   #444
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Re: Please turn your AIS off when docked/moored/anchored

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(I find it fascinating, parenthetically, how a few of you keep trying to re-frame the argument. Evans has stated that he sees this as being about community, specifically the cruising community, and how we use a commons. Why is that so difficult to accept?)
It isnt a 'commons' issue because the 'commons' simply is huge, there is no scarce resource here . There is no tragedy.

Evans had two issues

(a) Too many alarms from static class B boats

(b) His class B unable to get through in certain situations ( or missing tx slots)

I, and many others, would contend that (a) is a AIS receiver/AIS target display filtering issue and an SOP issue. ( alarms in high traffic area while conning boats, as Boatman has explained).

( the equivalent call to Evans commons, would be in high demand class A movements, that all class B vessels turn off their transmitters, I see no call for such action)


(b) This discussion has been focused on determining what effect class B trnsmissions have on the available AIS bandwidth, the consensus , from what little data we have, is that CLass B AIS in such situations has very little effect on the available bandwidth. Hence the call to turn them off ( from that bandwidth perspective, is not correct)

Evans can state what he likes, thats doesnt make it right, ( or wrong)
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Old 20-05-2013, 13:46   #445
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Quote:
Originally Posted by Bash View Post

As far as USA law is concerned, you are 100% wrong. Since the dawn of radio, USA airwaves have been considered a public commons, subject to regulation in terms of frequency use, transmission power, acceptable types of use, et cetera. That's how it's possible to come up with regulations excluding commercial traffic on certain high frequencies, restricting other frequencies to marine-only use, prohibiting pornography on broadcast TV, et cetera.

I'm guessing we all agree that Joe Schmoe ought not be using Marine VHF 16 to query whether "Anybody Else Out There" is catching any fish. But this may largely be a result of regulations restricting that channel to hailing and distress. At present, however, there are no regulations restricting the use of AIS frequencies by boats sitting fat and pretty in the dock. Evans has suggested that boats who do so, regardless of the fact it's not illegal, are abusing the commons.

You can howl all you want about how misguided you find estarzinger's arguments to be, but as long as AIS transmitters use public airways, a commons is involved.

(I find it fascinating, parenthetically, how a few of you keep trying to re-frame the argument. Evans has stated that he sees this as being about community, specifically the cruising community, and how we use a commons. Why is that so difficult to accept?)
How people can have such differing views, interresting is it? In my view, air waves are a natural phenomena, and thus have no nationality and can by definition never be a public commons. They are not different than a ray of light or a call from a bird.
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Old 20-05-2013, 13:48   #446
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Re: Please turn your AIS off when docked/moored/anchored

Since very early in the thread, "commons" has been a short form reference to the parable "tragedy of the commons". Someone pointed out back then that this short hand was wrong and might result in confusion or inaccuracies, but it continued because it was easier to type.

So you are correct that radio frequencies are using a commons, but incorrect that this is an example fulfilling the parable "tragedy of the commons".

Besides, Bash, both sides arguing this point gave it up eons ago. Why re-frame it now?

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Old 20-05-2013, 13:51   #447
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Re: Please turn your AIS off when docked/moored/anchored

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I'm guessing we all agree that Joe Schmoe ought not be using Marine VHF 16 to chat about whether "Anybody Else Out There" is catching any fish. But this may largely be a result of regulations restricting that channel to hailing and distress.
Yes but that only refers to calling channels , there is no specific control of other channels, but yes of course we all would agree that unneccessary VHF traffic should be avoided,

AND i have agreed from the start that all unneccessary AIS ( from any source) should also be avoided.

BUT thats not the same as Evans 'commons' argument, where he wants access to a resource , by denying it to others. ( since he cant tell there justifications for leaving them on!).
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Old 20-05-2013, 13:56   #448
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Re: Please turn your AIS off when docked/moored/anchored

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(I find it fascinating, parenthetically, how a few of you keep trying to re-frame the argument. Evans has stated that he sees this as being about community, specifically the cruising community, and how we use a commons. Why is that so difficult to accept?)
Bash, what we are discussing is whether the problem Evans was having was truly related to over-utilization of a scarce resource, or not. I think most of us have implicitly agreed to not argue the "selfish over-use of the commons" philosophical issue, since that was getting us nowhere, and most of us agreed that most of the time a docked boat may as well turn off its transmitter.

There are now two main areas we are cordially discussing:
1) Do Class-B transponders over-utilize the available AIS slots, and where do docked vessels fit into the equation. Was the original problem due to channel overloading (I personally think not), or some other factors (I think yes).

2) We are agreed that there is room for improvement in alarm and display filtering. How might these improved filters function? How and where do we use the tools we currently have?

This seems like a good discussion now, and I see no need to dredge up the moral aspects, at least not until we can decide if this is even the issue at play.
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Old 20-05-2013, 14:09   #449
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Re: Please turn your AIS off when docked/moored/anchored

Paul. I really think that the leisure market has been badly served by poor AIS receive only units , like the Standard Radio displays, and even the SIMrad and Vesper units. Heres why.

AIS on leisure vessels needs to proceed like the IMO mandated for AIS radar and ECDIS, we need to merely treat AIS transponders as black boxes , just like GPS feeding into our 'information display systems'

Hence the focus should be on the visual chart plotter/radar etc functionality.

heres was I believe should be looked at

(a) AIS is a visual system, users should seek to have a visual display overlaid on a chart , this is the simplest visual system to interpret. the brain is very powerful at visual clues. No AIS display should be invisible to the helmsmans, and if so should be turned off if it is ( alarms I mean) , cause 'down there ' its useless.

(b) Class B filters should have a speed filters , but always show targets inside whereever proximity area is set. ( outside that they dont display). if the speed filter is exceed they show regardless.

(c) It would be good to be able to highlight certain vessels and for the display to track these explicitly , often we are watching the 'bad boy', its takes time to reacquire these visually on the display.


I dont think we need specific class B or A filters, more filters based on actions ( or lack of actions) by any craft.

The other thing that should happen is chartplotters need to be more closely integrated to teh AIS transponders, stealth mode, AIS statistics, class B safety messages , display of AIS telemetry show be available on the chart plotter. weve suffered from the huge delay that nmea had in sorting out AIS PGNS

If we got halfthe way we have with MARPA/radar plotting and radar control on small chart plotters with AIS wed be making progress.

dave
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Old 20-05-2013, 14:16   #450
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Re: Please turn your AIS off when docked/moored/anchored

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Evans, I agree that San Francisco is not a high-traffic area, but we could probably extrapolate using the percentages I recorded.
Just FYI, the paper that Dave linked to a ways above, calculated that 182 class A ships with generate a 20% slot saturation (there are a lot of assumptions which they detail in the paper). I think that means that my Class B (randomly picking a slot) would not get out 20% of its messages.

If I scale that linearly to your SF class A count (just excluding the class B boats), I get a 12% slot saturation, which I would probably not even notice (re the 'message congestion' problem). Your location plots suggest I probably would also not have an 'alarm cluster' problem either. (Note: I have actually sailed in SF bay. We did not have AIS at the time. But I do remember that it was less congested with way fewer crossing interactions than I expected).

You have two proportions in your data. One is the A to B proportion. I am guessing this varies widely (eg way more B in Newport and more A in Balitmore). The other is stopped vs moving. I am guessing this will be more consistent across locations.

If I 'reverse scale' it to my 50% message drop-out along NYC I get 450 class A. . . . or some equivalent mix of A & B (the paper does not attempt to define a class B traffic equivalent). That seems like a lot of vessels - perhaps twice as many as I would have purely guessed - but the commercial shipping guys would have a better idea.

Some of you commercial guys could say for sure, but my guess is that the Solent and Singapore would be the perfect 'high traffic' cases with a high total number of both ships and yachts.
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