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Old 15-06-2014, 04:06   #136
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Re: Thoughts about AIS

Good case in point Dockhead...... and comes under the heading of "radar assisted collision"

Critical mistakes made by both captains were to make close quarter decisions in the fog based only on poor radar information.
No radio confirmations of intent, no 6 minute radar plotting by skipper before deciding to slow down.

Confusing change of speed rather than dramatic change of course.....all well inside a radar PAD. ( Planned Area of Danger)

Both Safe Speed and a safe CPA are quite different in the Fog.
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Old 15-06-2014, 04:18   #137
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Re: Thoughts about AIS

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Originally Posted by Dockhead View Post
All very good questions!

So -- first of all -- for those who have never done it -- crossing the English Channel (or the North Sea shipping lanes or similar areas of dense, fast traffic) is not anything you would call "close quarters". These are large bodies of water. Aside from the very end near the Dover Strait, the English Channel is no less than 60 miles wide.

So it's very different from maneuvering in harbors or entrances to anything. It's really much more like flying a plane, I think. You have to manage a whole lot of possible spatial conflicts, and you have to manage them efficiently, because there are so many of them. You can't call on the VHF and discuss every crossing because you would be overwhelmed. In the Channel, VHF calls from yachts are mostly just ignored. Really. Even if you use DSC. You can't custom design every crossing when you may have three or four crossings in the space of 10 minutes. You can't just dodge around -- the way we do in harbors and estuaries and harbor entrances -- because others have also made calculations based on our course and speed, and sudden moves on our part ruin the solutions of the ship watchkeepers.

Ship watchkeepers want, more than anything, smooth, predictable maneuvers on our part, made in accordance with the Colregs. This is another reason why I am loath to make otherwise useless course changes, just to observe whether the CPA to a particular ship increases or decreases.

Encountering a single ship in open water is rarely any kind of problem. With AIS, you are alerted to a close crossing from far away, and you can easily unwind it from a safe distance. Before the risk of collision exists, you are not required to hold course as speed if you would otherwise be the stand-on vessel, so you are free from 10 miles out, say, to make a course change which will prevent a close crossing from ever happening, even if you are under sail. And obviously this is good practice.

The difficulty arises when you have to deal with a number of ships at once -- which is typical in the kinds of places we're talking about. Here you can figure out somehow whether you're passing ahead or behind, and figure out the alteration of course which will resolve the situation, but that changes everything with regard to Ship 2 and Ship 3. To find a course which will keep you safely clear of all three can be very complicated, maybe requiring a lot of trial and error, and the absence of the information about whether you are passing ahead or behind can make it just about impossible to figure out efficiently.

Yes, with regard to any one ship, you could change the length of your COG extension lines until you get a picture of the relative positions at CPA. To do that (on my plotter, at least), you have to go into the setup menu and change them separately for own vessel and AIS targets. And you can't set them at just any length -- I have a choice of 1 min, 2 min, 10 min, 30 min, 60 min, and 120 min. This is a hell of a lot of fiddling to figure out one crossing, and really unfeasible to do it when trying to figure out a course to keep you clear of three vessels. You'd wear out the buttons on your plotter going back and forth between this ship and that ship to try to check the result of any possible course change. Maybe some people -- like Mark, perhaps -- can work out the proportion of the line based on speed and visualize the relative positions at CPA. If so, that's a real talent which I lack.

And imagine what you will do to the work of the watchkeepers on the ships -- who are also dealing with the same situation -- if you are jinking around, changing course, just to determine whether you are passing ahead or behind. They are trying -- just as you should be! -- to work out a course which will keep you at a safe difference from everyone, not violating anyone's "personal space" of one mile, without changing course in close quarters.


The Vesper system is totally different from what we have on our plotters -- showing you at a glance with no fiddling the relative positions at CPA with every ship of interest. For all of the reasons above, I consider this vitally important in a place like the Channel.
A useful radar technique when faced with many moving targets all dealing with multilateral conditions and course changes is to switch Radar to TRUE MOTION.
I use this when transiting through Singapore Straight where many vessels big and small, fast and slow are entering or leaving traffic lanes and overtaking.

You see the course changes right away and can better visualize the interactions ahead of you.
Takes a bit of practice and it is critical that you
remember what Mode you are in.
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Old 15-06-2014, 04:25   #138
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Re: Thoughts about AIS

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Originally Posted by Pelagic View Post
So "offshore" under sail but acting as the give way v/l you would make minor course changes from 10nm away?


What if the other v/l does the same in a way to cancel out your avoidance action?
Yes.

If they do the same there should be plenty of time to make an obvious course change.

At similar speeds I would decide if passing in front or behind is the most beneficial, also taking into account possible course or speed changes they may make due to rounding headlands, staying in channels, TSS, avoiding other craft etc.
If the other vessel is doing 1.5 - 4 times my speed and we are set to cross their bow at less than 1M I would always prefer pass behind and adjust course to suit, usually with at least .5M CPA. So assuming we are 10 M out and I want to adjust my course 1M to port to pass behind, thats about a 5 degree course change. Pretty acceptable at 10 miles out for either a sailing vessel or a vessel under power.

I think its better to take action as early as possible, especially when running downwind as course changes and speed changes can be much more difficult and unpredictable on a yacht. I also take bearings as soon as possible to double check what the electronics are telling me. Lets face it, crossing another vessel under sail can be pretty hit and miss. An expected crossing ahead of 1 mile from 7 miles out can easily decrease to a collision course if the wind picks up 4 knots and your speed increase 1.5 knots. If in doubt ..STOP
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Old 15-06-2014, 04:45   #139
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Re: Thoughts about AIS

Monte....each to their own, but as you rightly describe piloting a predicted course under sail is not very consistent with changes in both wind stength and direction common.

From the perspective of large power vessel in sight of a sailboat that will have a close CPA....they tend to ignore sailboats until within 5nm because of that 'shiftiness'
Hopefully ship should properly alter course to open CPA, but if not, at 3nm if I am on sailboat.... and they won't answer the radio..... I would make an obvious tack or course change and curse the ship...

And despite what many sailors say at the pub...... Most ships alter for sailboats.
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Old 15-06-2014, 04:46   #140
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Re: Thoughts about AIS

My "wish for a golden fish" is really to have simple info on the plotter screen telling me if I will cross the course of AIS target in front or behind. I believe that really all necessary data are already computed in the "black box" and we need only to have them displayed in reasonably obvious way.
What come on mind for me is just to have the icons for the vessels I'm to cross before their bows to be displayed in red instead of black for example, and may be to have a possibility to set a range circle for such displaying.
Next thing I'm thinking would be nice to have... On my screen when other vessel is closer than at a set distance it start to be displayed as a flashing icon. I really would prefer to have flashing icons of vessels with closer than set CPA.
Those two adjustments to displaying mode would give readily understandable picture of the whole situation on the water for me...
The only problem is, how to persuade the plotter manufacturers to make some (probably simple and easy) adjustments to the software...

Cheers,

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Old 15-06-2014, 04:52   #141
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Re: Thoughts about AIS

Quote:
Originally Posted by Pelagic View Post
Good case in point Dockhead...... and comes under the heading of "radar assisted collision"

Critical mistakes made by both captains were to make close quarter decisions in the fog based only on poor radar information.
No radio confirmations of intent, no 6 minute radar plotting by skipper before deciding to slow down.

Confusing change of speed rather than dramatic change of course.....all well inside a radar PAD. ( Planned Area of Danger)

Both Safe Speed and a safe CPA are quite different in the Fog.

Even in good weather and visibility, a mile is usually considered by most ship operators to be the minimum safe CPA:

"Fleet Instructions, which were on board P&O Nedlloyd Vespucci in accordance with ISM Code requirements, stated that close quarters situations should be avoided by early and substantial course alterations and that in open sea, plenty of room should be given to all traffic. In addition, they stated that a safe CPA was considered 1 mile or more in the open sea, but that the safest CPA should always be obtained."


The Fleet Orders also discourage the use of VHF in collision avoidance:

"5.1.1 Performing the navigational watch
In order to keep an efficient watch and safe navigation of the ship the officer
should ensure:

. . .

that he takes early and positive action for avoiding collision and that he
basically will not use VHF for collision avoidance purposes
."


This is in accord with the MCA's strong position against using VHF for collision avoidance:

http://www.dft.gov.uk/mca/mgn167.pdf

Marine Guidance Note 167



I understand all the arguments against using the VHF in a potential collision situation, but I don't personally make a dogmatic rule against it, and I do call up from time to time. That is because in a lot of conversations with professional mariners I understood that despite the risks, it can help to talk by VHF if you are confused about someone's intentions. Also, with DSC, one of the main risks of using VHF for this purpose -- namely that you will be talking to the wrong ship -- is greatly reduced.

However, I do think that the idea that if you have some problematic crossing you can just "call them up on VHF and sort it out" is deeply flawed. It is no kind of substitute for proper situational awareness and planning from a safe distance, and in my book, it's just one level above the "oh I'll just dodge out of the way if a ship gets too close" which is the main collision avoidance technique of a shocking number of cruisers.

First of all: if you have proper situational awareness, if you know, understand and follow the COLREGS, you should NOT except under exceptional circumstances be confused about the intentions of another vessel in the open sea. Especially not with AIS, where you can clearly see if a ship has changed course in order to safely avoid you (which usually takes place at 5 to 10 miles out, where it properly should take place).


Note also that in areas of heavy traffic, like where I sail, ships most often simply ignore VHF calls from yachts. They don't especially want to hear our stupid blather, and they don't especially want to discuss what should be obvious, and only the most polite and patient of them is really willing to talk us through a crossing on the radio. What they really want is for us to follow the COLREGS and avoid any sudden, unexpected maneuvers. This confirmed in dozens of conversations with professional mariners.
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Old 15-06-2014, 04:54   #142
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Re: Thoughts about AIS

Quote:
Originally Posted by DoubleWhisky View Post
My "wish for a golden fish" is really to have simple info on the plotter screen telling me if I will cross the course of AIS target in front or behind. I believe that really all necessary data are already computed in the "black box" and we need only to have them displayed in reasonably obvious way.
What come on mind for me is just to have the icons for the vessels I'm to cross before their bows to be displayed in red instead of black for example, and may be to have a possibility to set a range circle for such displaying.
Next thing I'm thinking would be nice to have... On my screen when other vessel is closer than at a set distance it start to be displayed as a flashing icon. I really would prefer to have flashing icons of vessels with closer than set CPA.
Those two adjustments to displaying mode would give readily understandable picture of the whole situation on the water for me...
The only problem is, how to persuade the plotter manufacturers to make some (probably simple and easy) adjustments to the software...

Cheers,

Tomasz
Yes! +1 on everything in this post.
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Old 15-06-2014, 05:13   #143
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Re: Thoughts about AIS

Quote:
Originally Posted by Pelagic View Post
Monte....each to their own, but as you rightly describe piloting a predicted course under sail is not very consistent with changes in both wind stength and direction common.

From the perspective of large power vessel in sight of a sailboat that will have a close CPA....they tend to ignore sailboats until within 5nm because of that 'shiftiness'
Hopefully ship should properly alter course to open CPA, but if not, at 3nm if I am on sailboat.... and they won't answer the radio..... I would make an obvious tack or course change and curse the ship...

And despite what many sailors say at the pub...... Most ships alter for sailboats.
I don't think you guys are actually disagreeing about anything.

I think we can all agree that when you're 10 miles out, say, and especially if you're under sail, and you can alter course to ensure that you will pass well behind a ship and ensure that no close quarters situation ever arises -- this is excellent seamanship and the right thing to do. If you have AIS and you are somewhere where you are encountering just one ship at a time, I think this is a big Plan A, and you might not ever need anything else.

I also totally agree with Monte that if a dodgy situation is developing -- if I expected the ship to change course but it didn't, and I can't raise them on the radio, that I would NEVER rely on a CPA of a few cables as calculated by my AIS (the exact mistake made by the ship's master in the Wahkuna case). I would tack or make an otherwise dramatic maneuver to just be damned sure that I don't get into a hairy close quarters situation. And I agree that 3 miles is just about the right distance for this -- certainly not less, and probably more in case of very fast moving ships.

The only thing I would be cautious about is the phrase "If in doubt, STOP". That is precisely what the skipper of the Wahkuna did!! Just stopping can be a great tactic, but it only works if you are SURE that the ship is passing ahead, or if you are far enough away that there's no risk that you will end up under the bows of the ship. A lot of cruisers assume that you can get out of any hairy situation with a ship by just stopping or dodging -- it's not true! To be sure that the ship is passing ahead, you not only need to have this information displayed (the problem which started this thread), but you need to be operating within the limits of the system's accuracy (the master's mistake in the Wahkuna disaster).
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Old 15-06-2014, 05:18   #144
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Re: Thoughts about AIS

Quote:
Originally Posted by Dockhead View Post

The Fleet Orders also discourage the use of VHF in collision avoidance:

"5.1.1 Performing the navigational watch
In order to keep an efficient watch and safe navigation of the ship the officer
should ensure:

. . .

that he takes early and positive action for avoiding collision and that he
basically will not use VHF for collision avoidance purposes
."


This is in accord with the MCA's strong position against using VHF for collision avoidance:

http://www.dft.gov.uk/mca/mgn167.pdf

Marine Guidance Note 167

.
I read that a bit different as a proper warning "not to be distracted by VHF when still in the process of maintaining a safe CPA...... Not a rule against trying to confirm the other vessels intentions when they appear to be ignoring COLREGS

However, I think local conventions have a large bearing. In the PNW, we all call up each other on the vessel traffic channels to confirm situations when dealing with blind corners and strong currents in frequent fog.
Then CPA's are much smaller and unavoidable.

Open ocean on a sailboat 2nm is my minimum comfort zone. No need to talk about that
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Old 15-06-2014, 05:33   #145
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Re: Thoughts about AIS

Sorry Dockhead...I didn't mean to distract from improving the AIS on screen information....

Just wondering if we are getting into AIS assisted collisions due to overconfidence with their use by some operators?
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Old 15-06-2014, 05:37   #146
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Re: Thoughts about AIS

Quote:
Originally Posted by Pelagic View Post
I read that a bit different as a proper warning "not to be distracted by VHF when still in the process of maintaining a safe CPA...... Not a rule against trying to confirm the other vessels intentions when they appear to be ignoring COLREGS

However, I think local conventions have a large bearing. In the PNW, we all call up each other on the vessel traffic channels to confirm situations when dealing with blind corners and strong currents in frequent fog.
Then CPA's are much smaller and unavoidable.

Open ocean on a sailboat 2nm is my minimum comfort zone. No need to talk about that
Ah, yes, I see what you mean.

But I actually agree with all of this. I also use VHF if a vessel simply seems to be ignoring the rules -- that's a legitimate case of confusion about intentions, notwithstanding what the MCA has to say about it. I think 90% of cases where cruisers are "confused about intentions" of a ship result from the cruiser's not understanding the rules, or not having been able to identify that the ship actually did alter course. That certainly was my own situation before I had AIS. I would get nervous about a crossing, would call up to see whether the OOW was intending to alter or not, so that I could take action instead of standing on. If the ship didn't ignore my call, I would most often hear that "yes I see you, I already altered course x miles ago, and I now have CPA with your vessel of x miles". With AIS you have a so much better view of all this that such confusion is less likely.

And I certainly agree that in a crowded harbor situation like what you describe the practical rules may be very different.


A little thread drift: Last month I transited the North Sea en route to the Kiel Canal, and passed through another of the world's busiest seaways -- the approach to the Elbe, which is where most Baltic shipping comes out to get to the rest of the world, and where probably 90% of German shipping comes in and out. They have a totally different approach -- they have something like Air Traffic Control and they direct all the traffic to prevent situations from developing. As you enter the controlled zone, you are required to log in with VTS, who then hand you over to Radar Control. They track you and order you to take this or that course, to speed up or slow down, and they tell you whether you are getting too close to this or that ship. Even though I had most of this information on my AIS display, I found it very cool and felt very safe and relaxed despite the incredibly intense traffic and poor visibility. Leave it to the Germans, I guess, to create supreme order in a situation which is chaotic in most other parts of the world
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Old 15-06-2014, 05:46   #147
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Re: Thoughts about AIS

That is the same thing I was talking about with Vancouver Traffic Control and Seattle VTS.....
it is wonderful.... they update you regularly on traffic around you, their ETA's at given points and even weather/fog and small craft around.

They even control and admonish those not following the traffic lane protocols.

This is the link that shows all the regions under radar coverage.
http://www.ccg-gcc.gc.ca/e0003910
Even though meant for commercial... on a yacht in the 70's we would call up and identify ourselves stating that we were "monitoring but not participating".
They always kept an eye out for us.
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Old 15-06-2014, 06:00   #148
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Re: Thoughts about AIS

Quote:
Originally Posted by Pelagic View Post
Sorry Dockhead...I didn't mean to distract from improving the AIS on screen information....

Just wondering if we are getting into AIS assisted collisions due to overconfidence with their use by some operators?
I haven't heard of any "AIS assisted" collisions, but I absolutely see the makings of them. So many cruisers refuse to learn how to do collision avoidance the way commercial mariners do it -- in a systematic, methodical way. And insist that "you are overf****g the problem; just dodge out of the way" or "just look at AIS and make sure you have a few cables of CPA and don't worry about it".

We already assume that GPS is infallible. I will be the first to admit that I do! Because it practically is infallible, but the charts are not, and you have to use your eyeballs and depth sounder and not just "drive the dot". It is a big fallacy to assume that because GPS is nearly infallible that other data we have derived from GPS also is -- like what your electronic charts says must be right in front of you.

I think AIS is the same thing -- the accuracy of the calculated CPA is taken as a given, and no thought is given to how much margin of error is needed in different situations. Exactly the mistake of the ship's master in the Wahkuna case. Don't worry about it; don't overf***k it -- just look at CPA on your AIS and forget about it. It's a variant of "driving the dot" with a chart plotter, with similar dangers, IMHO.
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Old 15-06-2014, 06:26   #149
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Re: Thoughts about AIS

Amen to that Dockhead.

On a recent delivery of a 69ft Ferettii for a friend.... I watched their newly hired captain (who was assisting me) ....stare trancelike at the latest Raytheon plotter hoping it would tell him what to do when a tanker was within 0.3 mile on a converging course at night in heavy rain.

Totally clueless about priorities and effective use of the latest electronics.

Since I had promised to assess him for the owners
Needless to say after a quick coversation with the owners.... he was fired!
Scary!
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Old 15-06-2014, 07:08   #150
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Re: Thoughts about AIS

Quote:
Originally Posted by Dockhead View Post
I haven't heard of any "AIS assisted" collisions, but I absolutely see the makings of them. So many cruisers refuse to learn how to do collision avoidance the way commercial mariners do it -- in a systematic, methodical way. And insist that "you are overf****g the problem; just dodge out of the way" or "just look at AIS and make sure you have a few cables of CPA and don't worry about it".

We already assume that GPS is infallible. I will be the first to admit that I do! Because it practically is infallible, but the charts are not, and you have to use your eyeballs and depth sounder and not just "drive the dot". It is a big fallacy to assume that because GPS is nearly infallible that other data we have derived from GPS also is -- like what your electronic charts says must be right in front of you.

I think AIS is the same thing -- the accuracy of the calculated CPA is taken as a given, and no thought is given to how much margin of error is needed in different situations. Exactly the mistake of the ship's master in the Wahkuna case. Don't worry about it; don't overf***k it -- just look at CPA on your AIS and forget about it. It's a variant of "driving the dot" with a chart plotter, with similar dangers, IMHO.
And we have gone there again! Yet another thread lost to fear of electronics being the cause of stupidity. Now it is AIS that has joined the ranks with integrated autopilots and GPS chartplotters? Worrying that if people get an AIS it will cause them to actually start running into things? Two posters here have actually said that! Making people stupid and causing them to forget other basic seamanship?

I think this always boils down to one thing - people unconsciously (or maybe even consciously) bothered that their higher perceived gained level of "ability" over others is easily wiped out by a technology. Therefore, they project that that technology causes problems and anyone using it (except them) are forced into lobotomies by it.

It seems to come down to whether one's self-image is threatened by a technology or not.

Mark
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