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Old 15-08-2015, 22:19   #151
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Re: AIS Do I Need It?

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Originally Posted by Ann T. Cate View Post
RC,

It's a little funny to me, the divergence. Jim, like Monte, found he wanted it above decks where it could be seen from the helm. In fact, if we were able to dim the display more, it would not have been a problem. I think AIS usage depends a whole lot on where you are. Family Van wrote that he has his barrier set at .5 mi. He is in a high AIS density area. On passage, over a very low density AIS area, ours was set at 24 mi., the idea being that that will alert the watchkeeper long in advance of needing to do something. Once you are aware of them, that's mostly what you need.

For you, singlehanding, you'll want to work out what area guard zone you'll want approaching Melbourne, a heavy traffic area, compared to Hobart. If I were you, I'd arrange to arrive with adequate daylight to get to your destination there, weather permitting, especially since it's winter.

Ann
Thanks Ann, I'm not singlehanding, not yet, one day, I'll have my son with me on this trip, who helped me originally sail it down from Adelaide.

Traditionally in Bass Strait I've had my AIS receiver set at 10miles with the CPA alarm at 5 miles. That seemed to work well enough on my last trip to Hastings.
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Old 16-08-2015, 00:10   #152
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Re: AIS Do I Need It?

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Originally Posted by FamilyVan View Post
I don't run around ramming in to other boats or islands. My electronics are installed for peace of mind, I don't use them on a regular basis. They are dry and out of the way downstairs, I consciously put them there.

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You're not alone. Our AIS display on a dedicated Garmin chartplotter is downstairs at the Nav station where it simply displays the "list." Upstairs at the helm, there's a very small AIS plotter on our Standard Horizon handset. We use our eyes first along with radar, then when we see something, we quickly figure out using eyes, binoculars and radar the directional heading of the vessel and if it will come close. If any questions, we take a look below at the display to see what it is.

Geez... Even without AIS you can still put a radio call out to the vessel on 16 if necessary. No different than if you have AIS. We're not sailing or motoring around trying to figure out constantly how close we can navigate to other vessels. We keep a safe distance and don't spend much time figuring or contacting.

No annoying calls to commercial vessels to announce our presence, no radio calls to other pleasure vessels... Just minding our own business enjoying the quiet with the AIS alarm turned off.
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Old 16-08-2015, 00:20   #153
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Re: AIS Do I Need It?

Sometimes radio comms with a big vessel nearby are indeed appreciated. A while ago we were sailing southward in the main channel entering Moreton Bay. A very large container ship was overtaking from clear astern, and it was apparent that we would arrive at the intersection with the Spitfire channel turn at about the same time. I called him to say that I would stay outside the channel as he passed and made the turn, leaving him the whole width to work in. He thanked me at the time, and then after completing the maneuver, called me again to say that he appreciated the gesture... had made his life much easier. I believe that it was the bay pilot talking, but not sure of that.

I can't see that this sort of comms are ever wrong or not indicated, despite the views of some of you posters. And AiS made it all so much easier...

Jim
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Old 16-08-2015, 00:34   #154
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Re: AIS Do I Need It?

zboss,

Speaking tactically, just move 5 miles offshore from the main paths: you'll get lots less traffic. It seems each individual skipper chooses waypoints for his course to maximize his speed for the course traveled. Since the shortest distance between 2 points is a straight line (great circle routes excepted), everybody's route is pretty similar; and ships do something similar to save fuel. It's easy to move outside it.

Ann
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Old 16-08-2015, 02:12   #155
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Re: AIS Do I Need It?

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Originally Posted by FamilyVan View Post
I'm not sure I fully support the hand bearing compass theory, I don't even have one on board. For a good mathematical solution to collision avoidance they help, but I'm not usually too interested in a mathematical solution.

If I'm the give way vessel, and I can deduce that I'm going to be crossing roughly 2 or 3 miles ahead of a large commercial vessel at sea, then I point my bow in a different direction, normally towards his stern.

These days I have my CPA alarm which gives me an early warning that I will be closer than desired to a passing vessel, which is great, but I still don't calculate a mathematical solution to the problem, I can, but I don't.

Mathematical solutions are great tools in your chest, but I believe the greatest benefit in learning how to calculate CPA and course or speed to achieve desired CPA (which was done on a RADAR plotting sheet when I studied) isn't the resultant mathematical solution, but the increased understanding of how ships interact on the water.

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Since you're an experienced pro, you probably started straight off with ARPA for collision avoidance, skipping the HBC technique which we are taught.

We don't use HBC for any kind of "mathematical solution" at all. The point of it is to detect changes in bearing which are not visible to the naked eye, so that you can detect a risk of collision situation and distinguish it from a safe passing, and distinguish passing ahead from passing behind, early enough to take action as you are required.

So what we do is observe the bearing with HBC every two or three minutes and observe the trend. It tells you pretty much all you need to know except TCPA, but the rate of change is a pretty good proxy for CPA.

Better yet, it tells you which way you're passing, so you know which direction to turn in order to increase CPA -- something my B&G set doesn't display (a flaw in my opinion).

Naked eyes and common sense are no more a substitute for this, than they are for a compass. You cannot observe North with your naked eyes; nor can you observe small changes in bearing at 5 miles.


As others have said, these questions affect different people sailing in different areas very differently. Many people have never been in a risk of collision situation in open water and just can't imagine what that is. In bays and harbors and inshore waters these situations don't arise. But in places where these situations arise regularly, everyone understands. I don't think anyone sails in the Channel without a hand bearing compass to hand in the cockpit, if there's no AIS on board. To cross the Channel without AIS and without HBC would be negligence per se.


But just because you rarely encounter such situations, doesn't mean you need to be willfully ignorant about how to deal with them. Just yesterday (!) I was under sail in the North Sea and found myself with a container vessel bearing down on me on a perpendicular course at over 20 knots with CPA of 5 meters. Because of the difference in speed, it looked from his aspect and bearing that I would pass far ahead -- there's naked eyes for you -- the naked eye can't judge speed at some miles away so the vague ideas about these which the naked eye give, are actually useless. But the AIS told the real story and even sounded an alarm.

I waited until about 4 miles out and decided to call him. The Indian watchstander had not seen me, although I was broadcasting AIS. He was just asleep at the switch, apparently with alarms switched off. A rare case -- these guys are pros -- but it does happen. And when he did look at his display and see me, he didn't think he needed to maneuver. So I tacked and made a hard turn to starboard -- and just in time. We passed just a few cables apart. At 20 knots, 4 miles goes by amazingly fast -- while you're establishing contact or thinking what to do or whatever. I can't imagine what would have happened -- this was just yesterday! -- in that situation with no AIS, no HBC, no knowledge or skill in collision avoidance. With a 5 meter CPA, the bearing would have been rock steady. At 4 miles out you could not see anything with your bare eyes to tell you what to do or whether you even have a problem. At 1 mile out you will see the problem with your naked eyes, but you are already in extremis. Your first, correct instinct will be a hard turn to starboard, but what if he's actually passing a cable ahead of you? You can't tell that with your bare eyes even at one mile and you've already got no time to figure anything out. In that case, and at that distance, a hard turn to starboard will put you right under his bows.

People, you cannot do this without knowledge and skill and some kind of tool, at least a hand bearing compass.


P.S. . . . and I got scolded by the Dutch Coast Guard for using Channel 16 for this short conversation. I did not want to waste time agreeing on a working channel with a half-asleep Indian watchstander and thought it was a matter of safety, but the Coast Guard emphatically disagreed.
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Old 16-08-2015, 02:21   #156
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Re: AIS Do I Need It?

Quote:
Originally Posted by Dockhead View Post
Since you're an experienced pro, you probably started straight off with ARPA for collision avoidance, skipping the HBC technique which we are taught.

We don't use HBC for any kind of "mathematical solution" at all. The point of it is to detect changes in bearing which are not visible to the naked eye, so that you can detect a risk of collision situation and distinguish it from a safe passing, and distinguish passing ahead from passing behind, early enough to take action as you are required.

So what we do is observe the bearing with HBC every two or three minutes and observe the trend. It tells you pretty much all you need to know except TCPA, but the rate of change is a pretty good proxy for CPA.

Better yet, it tells you which way you're passing, so you know which direction to turn in order to increase CPA -- something my B&G set doesn't display (a flaw in my opinion).

Naked eyes and common sense are no more a substitute for this, than they are for a compass. You cannot observe North with your naked eyes; nor can you observe small changes in bearing at 5 miles.


As others have said, these questions affect different people sailing in different areas very differently. Many people have never been in a risk of collision situation in open water and just can't imagine what that is. In bays and harbors and inshore waters these situations don't arise. But in places where these situations arise regularly, everyone understands. I don't think anyone sails in the Channel without a hand bearing compass to hand in the cockpit, if there's no AIS on board. To cross the Channel without AIS and without HBC would be negligence per se.


But just because you rarely encounter such situations, doesn't mean you need to be willfully ignorant about how to deal with them. Just yesterday (!) I was under sail in the North Sea and found myself with a container vessel bearing down on me on a perpendicular course at over 20 knots with CPA of 5 meters. Because of the difference in speed, it looked from his aspect and bearing that I would pass far ahead -- there's naked eyes for you -- the naked eye can't judge speed at some miles away so the vague ideas about these which the naked eye give, are actually useless. But the AIS told the real story and even sounded an alarm.

I waited until about 4 miles out and decided to call him. The Indian watchstander had not seen me, although I was broadcasting AIS. He was just asleep at the switch, apparently with alarms switched off. A rare case -- these guys are pros -- but it does happen. And when he did look at his display and see me, he didn't think he needed to maneuver. So I tacked and made a hard turn to starboard -- and just in time. We passed just a few cables apart. At 20 knots, 4 miles goes by amazingly fast -- while you're establishing contact or thinking what to do or whatever. I can't imagine what would have happened -- this was just yesterday! -- in that situation with no AIS, no HBC, no knowledge or skill in collision avoidance. With a 5 meter CPA, the bearing would have been rock steady. At 4 miles out you could not see anything with your bare eyes to tell you what to do or whether you even have a problem. At 1 mile out you will see the problem with your naked eyes, but you are already in extremis. Your first, correct instinct will be a hard turn to starboard, but what if he's actually passing a cable ahead of you? You can't tell that with your bare eyes even at one mile and you've already got no time to figure anything out. In that case, and at that distance, a hard turn to starboard will put you right under his bows.

People, you cannot do this without knowledge and skill and some kind of tool, at least a hand bearing compass.


P.S. . . . and I got scolded by the Dutch Coast Guard for using Channel 16 for this short conversation. I did not want to waste time agreeing on a working channel with a half-asleep Indian watchstander and thought it was a matter of safety, but the Coast Guard emphatically disagreed.
How do you set a '5' meter CPA? Mine only marks miles.
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Old 16-08-2015, 03:15   #157
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Re: AIS Do I Need It?

Quote:
Originally Posted by Jim Cate View Post
Sometimes radio comms with a big vessel nearby are indeed appreciated. A while ago we were sailing southward in the main channel entering Moreton Bay. A very large container ship was overtaking from clear astern, and it was apparent that we would arrive at the intersection with the Spitfire channel turn at about the same time. I called him to say that I would stay outside the channel as he passed and made the turn, leaving him the whole width to work in. He thanked me at the time, and then after completing the maneuver, called me again to say that he appreciated the gesture... had made his life much easier. I believe that it was the bay pilot talking, but not sure of that.

I can't see that this sort of comms are ever wrong or not indicated, despite the views of some of you posters. And AiS made it all so much easier...

Jim
I agree with you, although there are good arguments on the other side.

I was persuaded that radio calls are often useful by talking with professional ships' masters who unanimously told me that they would prefer to hear from us.

I really understand the MCA argument against radio calls, but I think they were formulated before AIS -- now that we can know for sure who to call, many of the downsides fall away.
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Old 16-08-2015, 03:29   #158
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Re: AIS Do I Need It?

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Originally Posted by Dockhead View Post
I agree with you, although there are good arguments on the other side.

I was persuaded that radio calls are often useful by talking with professional ships' masters who unanimously told me that they would prefer to hear from us.

I really understand the MCA argument against radio calls, but I think they were formulated before AIS -- now that we can know for sure who to call, many of the downsides fall away.
I call ships up, especially at night. They have never seemed to have minded. Mind you, they only seem to answer by calling them by name, identified by having an AIS.

And despite having a 36 foot steel yacht I've been amazed that twice I was told they couldn't spot me on their radar, even after I told them where I was. One of them was one of our two passenger ferries at around 2am. I put the anchor light on before he could physically see me and he still couldn't pick me up on his radar.
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Old 16-08-2015, 05:48   #159
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Re: AIS Do I Need It?

^^ pro tip . . . . if you have a woman's voice (Beth's) call a commercial ship . . . They will almost always answer (unless they are asleep or on the head) . . . . and want to chat.
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Old 16-08-2015, 06:23   #160
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Re: AIS Do I Need It?

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Naked eyes and common sense are no more a substitute for this, than they are for a compass. You cannot observe North with your naked eyes; nor can you observe small changes in bearing at 5 miles.
Well, this is what my naked eyes, and (un)common sense, typically tell me...

If I am unable to detect any change of bearing at 5 miles, a reasonably high probability of a collision risk already DOES EXIST...

Perhaps not always on paper, or a plotter/AIS display, but it still seems to me that having that seed planted IN MY MIND is a pretty vital first step...

;-)
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Old 16-08-2015, 07:51   #161
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Re: AIS Do I Need It?

Quote:
Originally Posted by Dockhead View Post
Since you're an experienced pro, you probably started straight off with ARPA for collision avoidance, skipping the HBC technique which we are taught.

We don't use HBC for any kind of "mathematical solution" at all. The point of it is to detect changes in bearing which are not visible to the naked eye, so that you can detect a risk of collision situation and distinguish it from a safe passing, and distinguish passing ahead from passing behind, early enough to take action as you are required.

So what we do is observe the bearing with HBC every two or three minutes and observe the trend. It tells you pretty much all you need to know except TCPA, but the rate of change is a pretty good proxy for CPA.

Better yet, it tells you which way you're passing, so you know which direction to turn in order to increase CPA -- something my B&G set doesn't display (a flaw in my opinion).

Naked eyes and common sense are no more a substitute for this, than they are for a compass. You cannot observe North with your naked eyes; nor can you observe small changes in bearing at 5 miles.


As others have said, these questions affect different people sailing in different areas very differently. Many people have never been in a risk of collision situation in open water and just can't imagine what that is. In bays and harbors and inshore waters these situations don't arise. But in places where these situations arise regularly, everyone understands. I don't think anyone sails in the Channel without a hand bearing compass to hand in the cockpit, if there's no AIS on board. To cross the Channel without AIS and without HBC would be negligence per se.


But just because you rarely encounter such situations, doesn't mean you need to be willfully ignorant about how to deal with them. Just yesterday (!) I was under sail in the North Sea and found myself with a container vessel bearing down on me on a perpendicular course at over 20 knots with CPA of 5 meters. Because of the difference in speed, it looked from his aspect and bearing that I would pass far ahead -- there's naked eyes for you -- the naked eye can't judge speed at some miles away so the vague ideas about these which the naked eye give, are actually useless. But the AIS told the real story and even sounded an alarm.

I waited until about 4 miles out and decided to call him. The Indian watchstander had not seen me, although I was broadcasting AIS. He was just asleep at the switch, apparently with alarms switched off. A rare case -- these guys are pros -- but it does happen. And when he did look at his display and see me, he didn't think he needed to maneuver. So I tacked and made a hard turn to starboard -- and just in time. We passed just a few cables apart. At 20 knots, 4 miles goes by amazingly fast -- while you're establishing contact or thinking what to do or whatever. I can't imagine what would have happened -- this was just yesterday! -- in that situation with no AIS, no HBC, no knowledge or skill in collision avoidance. With a 5 meter CPA, the bearing would have been rock steady. At 4 miles out you could not see anything with your bare eyes to tell you what to do or whether you even have a problem. At 1 mile out you will see the problem with your naked eyes, but you are already in extremis. Your first, correct instinct will be a hard turn to starboard, but what if he's actually passing a cable ahead of you? You can't tell that with your bare eyes even at one mile and you've already got no time to figure anything out. In that case, and at that distance, a hard turn to starboard will put you right under his bows.

People, you cannot do this without knowledge and skill and some kind of tool, at least a hand bearing compass.


P.S. . . . and I got scolded by the Dutch Coast Guard for using Channel 16 for this short conversation. I did not want to waste time agreeing on a working channel with a half-asleep Indian watchstander and thought it was a matter of safety, but the Coast Guard emphatically disagreed.
You are correct in theory, I started out not with an ARPA, but a cowled RADAR with grease pencil, which has the same effect as an ARPA in the sense that its more effective than an HBC for collision avoidance.

For collision avoidance with large vessels my go to strategy is attempting to deduce their destination by ship type, location presence of shipping routes vts zones etc. It might sound goofy, but it works pretty well most of the time. The system has a weakness in that you have to be familiar in the habits of mariners, but I think any one can do it with practice.

Yes I know this system is far from perfect, but I don't use it in isolation, I use it combined with other processes.

Edit: oh, and for clarity, I'm not a pro anymore, I gave up sailing commercially around the same time I joined cruisers forum, just after my son was born. Wouldn't want to misrepresent.

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Old 16-08-2015, 08:16   #162
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Re: AIS Do I Need It?

Obviously you can't observe north with your naked eye because it is impossible to see! It's a construct. You can observe the motion of vessels and fixed things in the water with your eyes. And you can make judgements if your vessel is going to have a (too close) encounter.

If you are sailing in congested waters with multiple hazards you need to pay close attention to the environment and less to some screen down below and I referring to single and short handed crew situations.

No will dispute the notion that more information about the environment is better than less. Having said that you need to manage all this information, process it and make way and stay out of the path of other vessels and avoid under water hazards and navigation aids. Obviously there is a point when you need to pay attention... and all the sophisticated navigation equipment will do no good. Look at what happened to the Costa Concordia.. which I am sure all sailors know about... https://en.wikipedia.org/wiki/Costa_Concordia_disaster.

Most of the collision avoidance I deal with is pleasure craft and weekend sailors not paying attention of not concerned... LOTS of them... and AIS is useless. And they often have their radars in service..
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Old 16-08-2015, 08:22   #163
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Re: AIS Do I Need It?

As someone who also started out with reflected plotter and grease pencil it became apparent that you were severely limited in the number of targets you could assess at one time.

So the temptation to infer the actions of another vessel were both encouraged (determining Aspect) but at the same time watchkeepers were tested and discouraged from making assumptions because of limited information as to the intent of the target in multilateral situations.

Luckily, these days with ground stabilized ARPA, Trial Maneuvers, AIS and synchronized charting, we don't need to guess any more.

Just stay out of those "Planned Areas of Danger" ( PADS)
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Old 16-08-2015, 08:39   #164
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Re: AIS Do I Need It?

Pelagic, I might be assuming too much, but I bet 9 times out of 10 you have already deduced your solution using traditional methods before you even walk over to your plotter to verify what you already believe to be true?

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Old 16-08-2015, 08:54   #165
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Re: AIS DO I NEED IT.?

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All AIS transponders come with a 'silence' switch as well
Not my Furuno FA-150, but in fairness to your point the current model does.
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