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Old 04-09-2016, 00:04   #181
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Re: AIS, Receiver or Transmitter

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You would never call the bridge of a ship and say "I'm stand on and need you to alter course", as in RWidman's ridiculous mischaracterization. You would ask what his intentions are, and you might even start out by saying "Do you see me? I'm not comfortable with our CPA and will now alter to port -- could you please hold your course and speed?" ............
Well, I wouldn't and you wouldn't...however I was following a solo round the world yacht person's blog a few years ago..... she would routinely call up ships in the middle of the ocean and tell them to keep at least 5 miles clear of her.

Mind you she also emailed Vendee(?) Race Control ( or whatever) in Paris or somesuch and told them to ensure that the entire fleet - then in the southern South Pacific - gave her a wide berth......
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Old 04-09-2016, 00:13   #182
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Re: AIS, Receiver or Transmitter

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My young and foolish days when I used to see how close I could get to the stern of a passing ship... Maybe I shouldn't admit that...
I still do it but I do show them green to green or red to red and then just keep tracking their stern.....
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Old 04-09-2016, 01:09   #183
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Re: AIS, Receiver or Transmitter

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He was probably quite happy with your 'less than a mile' but didn't want to you to get any closer........
Slight drift, but crossing the English Channel I've had ships alter course around me to give a CPA of almost exactly 1nm, and heard stories from others with the same. Wonder if that's on their standing orders?

Offshore they tend to complete any manoeuvres while still maybe 5 miles away. That's on a steel boat with good radar return, but no ais transceiver (one day soon... )
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Old 04-09-2016, 01:23   #184
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Re: AIS, Receiver or Transmitter

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Slight drift, but crossing the English Channel I've had ships alter course around me to give a CPA of almost exactly 1nm, and heard stories from others with the same. Wonder if that's on their standing orders?

Offshore they tend to complete any manoeuvres while still maybe 5 miles away. That's on a steel boat with good radar return, but no ais transceiver (one day soon... )
When I had the day job that was about what I worked on in ship/ship... varied of course depending on circumstances. Sooner the better if pos as less effort required.

If I was stand on 4 miles was the magic number where I knew I really really truly had to consider urgent implementation of 'plan B'....
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Old 04-09-2016, 01:24   #185
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Re: AIS, Receiver or Transmitter

Great believer of AIS transponders, however one must not forget the limitations of the class B units. They have low powered (2w) transmitters so have a theoretical max range of 5 to 10 miles, whereas class A units are 12.5 w transmitters and a much larger theoretical range. So you may see a large ship at 20 miles but he probably won't see you, this is assuming no base stations involved.
Maybe we should be contemplating installing class A systems, with all the added benefits such as messaging.

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Old 04-09-2016, 01:37   #186
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Re: AIS, Receiver or Transmitter

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Yes, that is what I was referring to.
Where I am we have a very active port and shipping lane close by. I was just out today and, as is common, a large car-hauling freighter peeled out of the port a mile and a half away. I say that because they ramp up to about 10 knots or more pretty quick. I guess because we are all used to it and know to stay out of the way, things go well. We know where they are headed and what they are doing. And then once in the shipping lane (seven miles away) they are not inclined to veer out of it. I did have one blast his horn at me once many years ago because he thought I was too close (less than a mile) I guess. So I defer to your rule of 3 or 4 miles, certainly, but here, for me, that is still quite a bit of room because we generally know where the bigger ships will be and to avoid them. So to be a mile or 2 from the shipping lane when one passes may not be unusual and I would say not considered hazardous by all concerned. The trick is though to be absolutely sure of where the shipping lane is! In the good ol' days of ded reckoning and RDFs and LORAN, if you had it, it was a lot more of an adventure! GPS, Radar and AIS (transceivers especially,) make everything so boringly safe now it's just no fun

That looks like perfectly reasonable practice to me.

As I've said a few times -- the problem is very different, if you have channels or shipping lanes. Just stay out of them; job done.


As to whether it is "boringly safe" now -- errrr, you should sail a day in my sea boots. In the English Channel and North Sea the traffic is so dense that you may be dealing with as many as 10 ships at the same time, that is, 10 ships with CPA of concern, and 100 ships within 10 or 15 miles of you. What is reasonably simple in an encounter between two vessels becomes exponentially more complex with several. They can be moving in all kinds of different directions at the same time -- ferry traffic crossing, long distance ships moving down the middle, coastal vessels following the ITZ. I honestly don't know how we did it before AIS and even with AIS you need to take notes and fully concentrate on it.
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Old 04-09-2016, 01:45   #187
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Re: AIS, Receiver or Transmitter

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Slight drift, but crossing the English Channel I've had ships alter course around me to give a CPA of almost exactly 1nm, and heard stories from others with the same. Wonder if that's on their standing orders?

Offshore they tend to complete any manoeuvres while still maybe 5 miles away. That's on a steel boat with good radar return, but no ais transceiver (one day soon... )
Yes, that's very typical.

1 mile minimum CPA is typically in their standing orders; 5 cables if they really need it (some obstacle, other traffic, etc.).

As Ping said -- they try to complete their maneuvers by 5 miles, and 4 miles is already a problem if CPA is still unsafe.


Note that vessel speeds influences all of this a lot. This would be for normal ships moving at 12 to 18 knots and works ok with other ships or with yachts making 6 to 9 knots. A big speed difference or very fast vessel like one of the 40 knot cat vessels means different procedures. Basically, if one vessel is much faster than another, there is little point of that vessel standing on, so the much faster vessel will not typically relinquish control of the crossing and will always maneuver itself.
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Old 04-09-2016, 01:53   #188
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Re: AIS, Receiver or Transmitter

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Great believer of AIS transponders, however one must not forget the limitations of the class B units. They have low powered (2w) transmitters so have a theoretical max range of 5 to 10 miles, whereas class A units are 12.5 w transmitters and a much larger theoretical range. So you may see a large ship at 20 miles but he probably won't see you, this is assuming no base stations involved.
Maybe we should be contemplating installing class A systems, with all the added benefits such as messaging.

Regards

Ab

My next boat will have Class "A" for sure.

The power is not so much the issue -- with a good antenna, ships will see you at 20 miles (and they still look at radar first anyway). The issue is frequency of updates. Class "B" sets only update every 30 seconds, so it's very hard for other vessels to see changes in course and speed.

I didn't do this earlier because of the hassle of putting voyage data in every time, but now I've seen plenty of vessels with generic voyage data if they are not going anywhere in particular, like "Cruising South Coast", so I think this need not be as burdensome as I thought.
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Old 04-09-2016, 02:43   #189
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Re: AIS, Receiver or Transmitter

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Well this paper http://helcom.fi/Lists/Publications/...ing%202012.pdf covering 2004/2012 in the Baltic suggests a general downward trend in ship/ship collisions over the period ...see Table 14...

Number of collisions between ships as a percentage of total number of ships out there and also - I think - in actual numbers has been decreasing for many years... starting with radar, then traffic routing , then ARPA, ECDIS, and now AIS... all lead an incremental decrease in casualties.

This report http://awsassets.panda.org/downloads...w_for_wwf_.pdf looks at 'total loss'.. 44 ships lost due to collision globally over a 15 year period.... mainly down to old ships and dodgy 'flags'... combine the two and you don't attract the cream of the crop as bridge watchkeepers.

How many collisions have been avoided due to AIS is like asking how many pedestrian accidents are avoided by people taking a day off work...who knows?

Thanks El., much appreciate it. Good stuff. I read through the reports. The first one does not report a decrease in collisions (which they define as ship to ship contact) within it's data range 2005 to 2012):

"Collisions have been the most common type of shipping accidents in 2011 and 2010 while in 2006- 2009 groundings were more common than collisions. In 2012 collisions accounted for 31% (47 cases) of all accidents which is the same percentage as for groundings and the collective category of other accidents. The number of collisions have stayed on the same level during the last three years (Figure 13)."

If you look at the graph the collisions rates for the last three years appear to me to be slightly higher than the reported average. Certainly no general decrease. The number of collisions, if on the decrease, is not apparent from this data.

The second report makes no mention of AIS (although it certainly discusses use of other tools). It references a general decline in incidents, but the vast majority are, as you say, "founderings" ascribed mostly to older vessels and those of dubious flagged countries (flags of convenience?). Not much help here on the AIS question.

Suggesting we can't study the impacts of expanding AIS adoption would be like saying you can't study the impact of seatbelt laws or motorcycle helmet use. THAT is a silly thing to say. And while this statistical analysis may not be easy, it should be relative statistical childsplay to isolate specific impacts of AIS from the other impacts. It's done all the time in far more complex statistical environments (public health, medical research, road safety ... The list is vast). So yes stinky, it's certainly possible to discern how many people have been saved, as you put it.

There is tons of excellent data kept on accidents in the US. The USCG is legally require to receive this information, and puts out detailed reports each year. If the adoption of AIS was such a safety boon, it would be discernible in the data. It may be there, but I've not found the study that shows it. It's such an obvious study to ask, what with the clear legal adoption requirement for commercial vessels. The expansion into the recreational world would be harder to factor in, but I would think simple sales data of AIS systems would be one source. I'm sure smarter people than me could come up with many methods to estimate rates of AIS use.

Insurance companies would be all over this stuff. If AIS were really such the no-brainer some of you keep calling it, where is the pressure from our insurers for clients to install them? They're certainly not shy about demanding other things when they believe it will reduce their payouts.

AIS is a useful tool. It appeals to our increasing screen-driven world. Use it appropriately for your waters, but for dog sake, look up every once it a while


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Old 04-09-2016, 03:03   #190
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Re: AIS, Receiver or Transmitter

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Thanks El., much appreciate it. Good stuff. I read through the reports. The first one does not report a decrease in collisions (which they define as ship to ship contact) within it's data range 2005 to 2012):

"Collisions have been the most common type of shipping accidents in 2011 and 2010 while in 2006- 2009 groundings were more common than collisions. In 2012 collisions accounted for 31% (47 cases) of all accidents which is the same percentage as for groundings and the collective category of other accidents. The number of collisions have stayed on the same level during the last three years (Figure 13)."

If you look at the graph the collisions rates for the last three years appear to me to be slightly higher than the reported average. Certainly no general decrease. The number of collisions, if on the decrease, is not apparent from this data.

The second report makes no mention of AIS (although it certainly discusses use of other tools). It references a general decline in incidents, but the vast majority are, as you say, "founderings" ascribed mostly to older vessels and those of dubious flagged countries (flags of convenience?). Not much help here on the AIS question.

Suggesting we can't study the impacts of expanding AIS adoption would be like saying you can't study the impact of seatbelt laws or motorcycle helmet use. THAT is a silly thing to say. And while this statistical analysis may not be easy, it should be relative statistical childsplay to isolate specific impacts of AIS from the other impacts. It's done all the time in far more complex statistical environments (public health, medical research, road safety ... The list is vast). So yes stinky, it's certainly possible to discern how many people have been saved, as you put it.

There is tons of excellent data kept on accidents in the US. The USCG is legally require to receive this information, and puts out detailed reports each year. If the adoption of AIS was such a safety boon, it would be discernible in the data. It may be there, but I've not found the study that shows it. It's such an obvious study to ask, what with the clear legal adoption requirement for commercial vessels. The expansion into the recreational world would be harder to factor in, but I would think simple sales data of AIS systems would be one source. I'm sure smarter people than me could come up with many methods to estimate rates of AIS use.

Insurance companies would be all over this stuff. If AIS were really such the no-brainer some of you keep calling it, where is the pressure from our insurers for clients to install them? They're certainly not shy about demanding other things when they believe it will reduce their payouts.

AIS is a useful tool. It appeals to our increasing screen-driven world. Use it appropriately for your waters, but for dog sake, look up every once it a while


Why go fast, when you can go slow

With sincere respect , I don't think you're looking at this in the right way.

Collisions at sea are fairly rare but when yachts are involved, usually fatal. So this is a low probability but very high consequence type of risk.

Furthermore, the system of collision avoidance is set up so that one vessel can be sailed by a completely clueless idiot, and as long as only one vessel follows the Rules, there will be safety (one of the ingenious aspects of the COLREGS).

That means that large numbers of recreational sailors sail around with absolutely no clue about how to detect a risk of collision situation, much less how to deal with it correctly, but it generally works out ok because the other vessel just deals with it.

But that doesn't mean that this is OK. We should be playing our part in the system. It will improve safety for sure, but maybe not immediately visible in the statistics. But it is also just simple consideration for professionals who have to deal with crossing with us.

It's not right to disparage AIS as some kind of "screen-driven" shortcut. There is no way to get even approximate idea of how you're crossing with another vessel with your bare eyes. The AIS screen is giving you crucial information which you can't get any other way, other than diligent use of a HBC, and even that can't be used on more than one or two targets at once. Commercial ships didn't need AIS all that much (and this is surely the main reason why we don't see a more dramatic effect in the stats) because they have big radars and ARPA, which has been giving them the same information for decades, but radars on small boats are not capable of doing useful ARPA.

What all that means is that AIS is THE tool which finally makes it possible for us to participate meaningfully in collision avoidance, rather than just relying on ships to avoid us.

As to whether you need to be broadcasting it or not, as opposed to just receiving it -- you won't be surprised to hear that I am a strong advocate of broadcasting it, but when dealing with ships and their powerful radars, it's probably not essential, so long as you have a good radar reflector. An AIS receiver is practically irreplaceable; the transmitter not so much. I would still never dream of saving a couple hundred bucks on this.


As to "looking up once in a while" -- it depends. Someone should be always be keeping a visual watch (as the Rules require!), but most effective collision avoidance, like other similar tasks (air traffic control, managing a flight of military aircraft), is done with total concentration and without distractions of extraneous visual information. When we are doing something really difficult, like the Dover Straits or Elbe approaches, where there may be 10 risk of collision situations at the same time, I do it from the nav table, fully concentrated on the radar screen, with OpenCPN on a different screen showing AIS data, and with pencil, paper, protractor, and radio near at hand. Head definitely "buried in the screen", where it should be for such a task. In this case it is not "screens", but the "Mark I Eyeball", which is seriously overrated.
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Old 04-09-2016, 06:05   #191
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Re: AIS, Receiver or Transmitter

With equal respect DH, your entire response here is predicated on the assumption that AIS has been a great boon to safety at sea for the recreational mariner. I'm saying there has been enough time with AIS to show whether this is a true statement or not. I'm suggesting the lack of such evidence, or indeed any impact in the one area you'd expect to respond quickly, that of insurance, is highly suggestive that AIS has not made much of a positive impact.

Before we go bananas over this new tool, and start claiming its the best thing since sliced bread, don't you think reasonable to ask for actual evidence as to its efficacy?

And just to be clear, I did not disparage AIS as some screen-driven shortcut. My comment is to suggest this technology's uptake (much like chartplotters) is related to our increasing screen-driven world. It's a technology that fits the times.

As I've said, I agree with everything you say regarding COLREGS, and the proper application of these rules. I also agree with you when you say (quoting skipmac) "COLREGS do NOT contradict common sense. On the contrary, they are the embodiment of centuries of wisdom and experience." The vast, vast majority of mariners, even if they can't quote chapter and verse of the specific COLREG involved, manage just fine. It's unfair and unsupported for you to say "it generally works out ok because the other vessel just deals with it." You keep assuming sailors aren't participating in collision avoidance, and I guess haven't done so up till now? This is a hugely disparaging remark on the generations of people who have gone to sea before AIS. It deserves actual evidence.
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Old 04-09-2016, 06:40   #192
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Re: AIS, Receiver or Transmitter

I'm currently cruising the Thousand Islands. There are innumerable passenger tourisy boats moving very fast through restricted waters. Like most large vessels I encounter, they do not move out of the way of smaller, slower craft; COLREGS be damned. AIS should be great here so I could time my sailing passages to avoid coming close to these large vessels in some of the very tight waters.

But despite there being a legal requirement, and despite operating in some very busy waters, almost none of these passenger boats broadcast an AIS signal. They're supposed to, but if you relied on this fact, you'd be putting yourself and your vessel at risk.

AIS is a useful tool. I like it. Like my chartplotter(s), it gives me useful information. But I don't depend on it as my sole, even most important collision avoidance tool. If I did, I'd be dead
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Old 04-09-2016, 06:50   #193
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Re: AIS, Receiver or Transmitter

This thread makes me believe that receive only AIS units should be made illegal and banned from the waterways. Some of the attitudes here are very reflective of the me, me me culture of people who want things for free without giving anything back.

"Give me your position, speed and course, but I'm not going to give you anything"

Banning AIS receivers would be a great benefit to those people who do not yet have AIS and those who want to upgrade to transceivers. Increased production and sales of AIS transceivers will drive down the costs.
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Old 04-09-2016, 06:56   #194
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Re: AIS, Receiver or Transmitter

Wrong.

As soon as you make one thing banned the price of a substitute good goes up, not down.

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Old 04-09-2016, 07:02   #195
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Re: AIS, Receiver or Transmitter

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With equal respect DH, your entire response here is predicated on the assumption that AIS has been a great boon to safety at sea for the recreational mariner. I'm saying there has been enough time with AIS to show whether this is a true statement or not. I'm suggesting the lack of such evidence, or indeed any impact in the one area you'd expect to respond quickly, that of insurance, is highly suggestive that AIS has not made much of a positive impact.

Before we go bananas over this new tool, and start claiming its the best thing since sliced bread, don't you think reasonable to ask for actual evidence as to its efficacy?

.....

So, to further your position, you propose a strawman that equates to a 'fool's errand' looking for positive evidence of AIS worthiness before acknowledging it's value. Why no use of common sense for this question?

I suggest that the data you are asking for sits next to the data on how many lives are saved by jacklines, harnesses, and tethers. Would that tethered crew member have gone overboard without the tether? Would that near miss have been a collision without AIS? Neither answer is recorded anywhere. It is certainly a fool's errand to go searching for such data, and you know that.

There is no data telling us the percentage of collisions per vessel mile of passage. Passages by pleasure vessels don't get recorded. What we do know is there are more vessels on the water this year than last year and the year before.

I'll state it again - Collision avoidance is a multiplayer activity and the more pertinent information each player has, the better the chances are to avoid a collision. Anyone with a half-ounce of common sense realizes this. Allowing a vessel to see/know your intentions within it's 'ability to maneuver scope' always works best for all involved. Do you not agree????
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