Over-Reliance on AIS -- Collision off Dungeness

[Exile]

OK, got it. What you've described sounds totally aligned with at least my understanding of the Rules. At 15 miles out with a close CPA revealed only by AIS & not eyesight, there's no actual risk of collision so you are free to maneuver and probably should given the examples you described. But at perhaps 10 miles or so, and within eyesight, the oncoming ship is likely to have already done her maneuver. So depending on traffic and openness of the water, etc., it's more likely time to stand on and allow the ship the next opportunity to alter course. Only if she fails to do so would you then want to alter your own course in time to avoid a collision. At that point, of course, hopefully the radio has cured any confusion.

[Dockhead]

Originally Posted by Exile

OK, got it. What you've described sounds totally aligned with at least my understanding of the Rules. At 15 miles out with a close CPA revealed only by AIS & not eyesight, there's no actual risk of collision so you are free to maneuver and probably should given the examples you described. But at perhaps 10 miles or so, and within eyesight, the oncoming ship is likely to have already done her maneuver. So depending on traffic and openness of the water, etc., it's more likely time to stand on and allow the ship the next opportunity to alter course. Only if she fails to do so would you then want to alter your own course in time to avoid a collision. At that point, of course, hopefully the radio has cured any confusion.

Yes, indeed. And the radio is not really essential if your moves are properly timed and calculated. The Rules allow you to stop standing on well before the situation gets really dangerous. In open water if dealing with only one ship at a time, I might stop standing on by 3 or 4 miles out, and I might not bother with the radio. I would make a single, dramatic change of course, and be very sure the ship is not turning at the same time.

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[Polux]

Originally Posted by monte

A bit Of confusion above. Some mentioned 1mile, 5 miles etc. They are referring to the CPA distance and distance to CPA, though not very clearly. I do t think Polux radios ships if the CPA distance is 5miles, but rather he does it 5miles before a close CPA distance. Likewise, Mark doesn't wait till the ship is 1 mile off his bow before calling, he does it when the CPA distance shows under 1 mile in some situations...

No he has been quite clear about it:

Originally Posted by MarkJ

Pollux,....
I certainly don't ring up ships at 5 nms. If at all its about 1nm or so.
..

On coastal waters, with heavy traffic no meaning in calling by VHF a ship that is at less than 3nm out of the CPA since most ships on those conditions, versus a small sailing boat, take avoidance course at about 3nm of CPA, as it was stated by Nigel and showed on the map posted by Mark regarding 3 different ships and himself.

You have to give time for the ship to change course.

Besides he also said:

Originally Posted by MarkJ

Don, don't be naughty. Of course he's not getting his life on it.

The stand on vessel has the ability to take evasive action till quite late.
I certainly do make plans in case the ships crew are asleep on the bridge... but not till quite close and after I have tried to contact via VHF

And I don't think quite close and evasive action quite close are conform with a VHF contact with the ship at 5nm regarding CPA.

Regarding me I only radio ships when I cannot avoid a situation where COLREGS have to be applied, even if that sometimes happens regarding having several boats relatively near to whom I could not avoid to be on a possible collision course or when I am restricted on my ability to maneuver (by Islands for instance).

If it is the case then I act not very differently than Mark, go by COLREGS rules, if not motoring and if it is the case, I assume the stand on vessel status and I do give time for the ship to alter course and that means I will only VHF if in doubt and with the ship at about a bit less than 2nm from CPA.

Originally Posted by MarkJ

Pollux,
I disagree that the constant changing speed and course is as problematic as you describe because AIS only transmits once per 30 seconds so the effective plot is fairly well averaged.
My speed doesn't vary up to 9kts... I start dancing at 7 but, yes, that means speed can easily double, and course too. But it certainly has not made any difficulties.

Mark, regarding the need to maintain speed and course while stand on vessel, as by the COLREGS, the fact that the AIS only transmits once in 30s is irrelevant.

If I am at 3nm from a ship on most cases CPA will happen in 10m or so and on the light coastal conditions I described it is easy, specially if the coast is not far to pass in some minutes from 5k wind to 9k wind and some minutes later to 5 or 4k wind.

That means that regarding my boat the ship can have taken a alteration of course regarding a course and speed that was being constant for many minutes at 4k when just after they have made that change of course a small increase of wind (to 9K) would increase my boat's speed to almost the double (over 7k).

The same can happen with medium to strong winds sailing downwind when the speed can easily pass in some performance cruising boats from 8.5K to over 10k without a big increase of wind and in just some minutes. There is a frontier between semi-planning speeds and hull speeds. When that frontier is passed the speed increases rapidly by some knots.

A stand on vessel cannot due that and the Ship would have rightfully considered that the sailboat is doing what he should do regarding COLREGS. Not assuming a constant course and speed as the Stand on Vessel is not only a violation of COLREGS but a dangerous thing to do.

[Dockhead]

Originally Posted by Polux

. . .
A stand on vessel cannot due that and the Ship would have rightfully considered that the sailboat is [not?] doing what he should do regarding COLREGS. Not assuming a constant course and speed as the Stand on Vessel is not only a violation of COLREGS but a dangerous thing to do.

I would not overthink this. The Rules do not assume that you must do something, which you cannot. Commercial mariners understand that boats under sail, especially going upwind, can't sail as steady course and speed as other vessels can. The predicted CPA from ARPA or AIS will be jumping around, and they simply compensate by steering a wider berth. It's not hard to distinguish a boat which is intentionally changing course, from one which is just pushed around by gusts and so forth; you just consider the average course and speed so it's really not that big a deal.


But this is just one more reason to NEVER make small course changes when you are in sight of a ship and are doing collision avoidance. It causes confusion especially when you are on a sailing vessel, since the course of vessels under sail anyway varies. Confusion is dangerous.

[Robin3]

Perhaps with a boat that performs like like Pollux's does in the moderate winds stated we should only go into busy shipping areas under engine alone and then only with cruise control and a top end autopilot engaged.[/SARCASM]

[Exile]

Originally Posted by Dockhead

I would not overthink this. The Rules do not assume that you must do something, which you cannot. Commercial mariners understand that boats under sail, especially going upwind, can't sail as steady course and speed as other vessels can. The predicted CPA from ARPA or AIS will be jumping around, and they simply compensate by steering a wider berth. It's not hard to distinguish a boat which is intentionally changing course, from one which is just pushed around by gusts and so forth; you just consider the average course and speed so it's really not that big a deal.


But this is just one more reason to NEVER make small course changes when you are in sight of a ship and are doing collision avoidance. It causes confusion especially when you are on a sailing vessel, since the course of vessels under sail anyway varies. Confusion is dangerous.

Helpful and I think needed clarification. Speaking from my own learning curve and from what I often hear from others, I think there may be a tendency to underestimate the capabilities of commercial shipping and assume those capabilities are the same as our small, recreational vessels. To this end, it's been most helpful reading first & second-hand perspectives from commercial captains & crew.

For example, I often hear claims from fellow recreational sailors that commercial ships "filter AIS-B transmissions out," when I think the reality is that they may just turn off their AIS-B alarms when approaching busy coastal areas & harbors for the very valid reasons you & others have described. On the other hand, we all know that small, fiberglass sailing vessels can be hard to see & make for lousy radar targets, so it's important not to presume too much (i.e. wait too long) when you're standing on, esp. if you don't have an AIS transponder. To that end, your suggestion of making your course change at 3-4 nm in open water may often be reasonable, taking into account your stated provisos that is.

I think your example of crossing the English Channel & Monte's in open water are good ones because they represent opposite ends of the spectrum. The Colregs are purposely unspecific about distances or time, however, because they can't possibly devise more specific rules to account for all the different variables & scenarios in between.

[Simonsays]

Originally Posted by Robin3

Perhaps with a boat that performs like like Pollux's does in the moderate winds stated we should only go into busy shipping areas under engine alone and then only with cruise control and a top end autopilot engaged.[/SARCASM]

just hire Boaty, he will bring you through asleep.

[Dockhead]

Originally Posted by Exile

. . . . The Colregs are purposely unspecific about distances or time, however, because they can't possibly devise more specific rules to account for all the different variables & scenarios in between.

Indeed.

The MAIN principle of collision avoidance is to avoid uncoordinated, simultaneous maneuvering, so although the distances and timing of collision avoidance maneuvering is not specified anywhere, you have to understand how it's done on ships under different circumstances. Most recreational sailors underestimate the decision-making horizons on ships, so usually, their decision-making horizons need to be increased.

The other essential thing is to be able to distinguish a safe CPA from a real collision course -- sorry to keep harping on this. It's really quite disastrously disruptive to the process, when these two factors combine so that WAFIs maneuver at the wrong time (thinking they are free to maneuver because risk of collision hasn't arisen yet, but in fact the ship has already maneuvered and is counting on your standing-on), and maneuver unnecessarily (ship has already set up a safe CPA, but you are not capable of determining that, so follow the "when in doubt assume there is a problem" role), and unfortunately this is pretty typical.


It's really too bad that recreational AIS doesn't typically display ROT of AIS targets -- this is extremely useful information, as you see immediately if the ship is turning or if its holding its course. OpenCPN is just wonderful for this, as it shows arrows with varying numbers of barbs, to show for every AIS target in what direction and how fast its turning. Together with the graphic display of the geometry of crossings, this makes OpenCPN a really superlative collision avoidance tool.

I wish recreational plotters could have a function which would set off some kind of alarm, at least flashing and bolded AIS target symbol, when a vessel in a certain proximity is turning. That would alert you to a case where you thought the ship was holding its course but in fact it starts to maneuver. Would be a real enhancement to safety.

[Jim Cate]

It's really too bad that recreational AIS doesn't typically display ROT of AIS targets

Actually, DH, all the Vesper units with which I am familiar do exactly that: ROT is displayed numerically, and as you say, it is useful.

Jim

[Dockhead]

Originally Posted by Jim Cate

Actually, DH, all the Vesper units with which I am familiar do exactly that: ROT is displayed numerically, and as you say, it is useful.

Jim

Excellent! I've never used a Vesper AIS, but they sound really great. It's too bad that AIS display on our plotters doesn't show any of these things.

[MarkJ]

Originally Posted by Exile

I think there may be a tendency to underestimate the capabilities of commercial shipping ...

I agree with you.
They are all professional, competent and caring of small boats, when they can be seen.

This doesn't include some Indonesian ferry drivers and Greek coasters and ferrys. The Indonesians are diabolical.

But in the 'normal' areas of the world I have fund them all great. (no, that doesn't mean I rely on them to be great).

With AIS its easier for us to be seen by them. It makes their job easier. and ours too

[Muckle Flugga]

Originally Posted by MarkJ

I agree with you.
They are all professional, competent and caring of small boats, when they can be seen.

This doesn't include some Indonesian ferry drivers and Greek coasters and ferrys. The Indonesians are diabolical.

But in the 'normal' areas of the world I have fund them all great. (no, that doesn't mean I rely on them to be great).

With AIS its easier for us to be seen by them. It makes their job easier. and ours too

Too right. Ferrys awful, tugs even worse. And the rest... Indonesia is definitely the Wild East, navigationally, in terms of COLREGS (more or less do not exist). Has to be experienced to be believed!

[MermaidMuse]

From a sailing perspective this thread has been quite interesting and educational. From a swimming perspective, you fellows are just going to have to learn to share the seas.....

Originally Posted by Muckle Flugga

Dover is definitely hectic. When passing through the straits in a N/S direction, I am often amazed at the fact that at any one time there may be more than one attempt to swim the straits. I mean, I understand back in the day when it was unique and all, but now? It just seems barmy. Each to their own I suppose but I have little doubt it annoys heck out of OOWs.

Originally Posted by Dockhead

Swimming the Dover Straits is pure madness. Bobbing around out there at 1 or 2 knots, totally invisible to traffic? I guess swimmer must have chase vessels with AIS and radios to try to warn off approaching ships? If I were the UK Home Secretary, I would forbid that practice.

Originally Posted by Muckle Flugga

Yep. Guard vessels. It is so common there is a small industry around it. And they broadcast their position on VHF annoyingly frequently, plus, if I remember right, transmit some kind of symbol on AIS. And yes. [IMG]file:///C:/Users/Suzanna/AppData/Local/Temp/msoclip1/01/clip_image001.gif[/IMG]

Open water endurance swimming is an international Olympic sport and a very popular recreational sport (one of the fastest growing ones).

The Dover Straits are the preferred crossing point for swimming the English Channel, which is part of the Triple Crown of Open Water Swimming.

A coast guard permit is usually required for swims that cross shipping lanes and the various swimming organizations that help coordinate swimmers and support boats do try to minimize disruptions to shipping.

Swimmers must have demonstrated sufficient swim speed and endurance to join these swims. Slow swimmers are picked up by support boats if they don't make sufficient progress in a timely manner.

Most of my sailing buddies are also open water swimmers or surfers. It is usually very obvious when we are sailing with someone who is not a waterman/woman as there is much that we see that they do not see when on watch.

[Muckle Flugga]

Originally Posted by MermaidMuse

From a sailing perspective this thread has been quite interesting and educational. From a swimming perspective, you fellows are just going to have to learn to share the seas.....







Open water endurance swimming is an international Olympic sport and a very popular recreational sport (one of the fastest growing ones).

The Dover Straits are the preferred crossing point for swimming the English Channel, which is part of the Triple Crown of Open Water Swimming.

A coast guard permit is usually required for swims that cross shipping lanes and the various swimming organizations that help coordinate swimmers and support boats do try to minimize disruptions to shipping.

Swimmers must have demonstrated sufficient swim speed and endurance to join these swims. Slow swimmers are picked up by support boats if they don't make sufficient progress in a timely manner.

Most of my sailing buddies are also open water swimmers or surfers. It is usually very obvious when we are sailing with someone who is not a waterman/woman as there is much that we see that they do not see when on watch.

Hey, I swim most days when in a good clean anchorage, usually a mile or more. Been a freediver for many years (a quarter century) and used to train several times a week for that, also do it in cold water/high latitudes (up to 60N). So… nothing wrong with swimming in the sea… but I do think that swimming across one of the top couple of busiest stretches of commercial traffic straits in the world is a bit absurd. I mean… why there? I know there was a historical cachet to it, but frankly there are hundreds of potential swimming passages which are every bit as challenging and more so and simply haven't been done, in many cases, and in many other major ones, perhaps only once in history. I have just done a handful of searches and only in the last 3 or 4 years have the Irish Sea, Pentland Firth, and Minch have been swum across, for the first time in history in each case. As to the channel? I mean, now a guy called Kevin Murphy holds the record for having swum it 34 times! But this is dwarfed by a girl called Alison Streeter, who has swum it 43 times… Really?

[Dockhead]

Originally Posted by Muckle Flugga

Hey, I swim most days when in a good clean anchorage, usually a mile or more. Been a freediver for many years (a quarter century) and used to train several times a week for that, also do it in cold water/high latitudes (up to 60N). So… nothing wrong with swimming in the sea… but I do think that swimming across one of the top couple of busiest stretches of commercial traffic straits in the world is a bit absurd. I mean… why there? I know there was a historical cachet to it, but frankly there are hundreds of potential swimming passages which are every bit as challenging and more so and simply haven't been done, in many cases, and in many other major ones, perhaps only once in history. I have just done a handful of searches and only in the last 3 or 4 years have the Irish Sea, Pentland Firth, and Minch have been swum across, for the first time in history in each case. As to the channel? I mean, now a guy called Kevin Murphy holds the record for having swum it 34 times! But this is dwarfed by a girl called Alison Streeter, who has swum it 43 times… Really?

Amen!

No one is against "sharing the sea", but swimming the Dover Straits is daft! That would be like routing your Olympic 400 yard dash event right across the M25 at rush hour!