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Old 20-08-2007, 09:21   #16
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Having conned 600 feet / 20,000 gross tons into Hong Kong harbor more than once.... I have to disagree with the "too much clutter" argument.

True, your sensors will give you too much data to sift through - but you have the same problem with radar in that situation. By the "too much clutter" argument no ship would ever transit the Straits of Mallaca with radar turned on - but they all use it religiously.

In any high-density traffic situation the primary means of collision avoidance (and navigation to a lesser extent) is the good old MK1 Mod 0 eyeball. I don't care what the data source is - lookouts, radar, fathometer, AIS, whatever - you simply define the moving circle around your ship and your intended track and concentrate upon that area. Ignore everything else and focus upon what is most important. The law of gross tonnage (otherwise known as Vessel Constrained by Draft) takes care of the pleasure boaters.

What distinguishes the good ship drivers from the bad ones is their ability to process LOTS of data quickly and determine the best course of action. To remove information from any sensor and deny the conning officer the opportunity to make a decision based upon that information could be a grave mistake. I've seen many deck officers get into trouble after telling the navigation team to stop reporting soundings, for example, because the deck officer was "too busy" to take routine reports.

Yes it's a pain in the neck. Yes you need to concentrate. Yes that jet ski is of little concern at 2000 yards. But for me - don't EVER deny me the opportunity to make a fully-informed navigation decision. Let me sort out what's important - and the more information I can get, the better decisions I'm likely to make.

Situational awareness ..... gotta have it! Can't do it right without information!

My $0.02.
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Old 20-08-2007, 09:35   #17
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AIS

I sail the PNW and use my AIS thankfully to help know where the big ships are, especially when the fog sets in. I REALLY REALLY don't want to have hundreds of recreational boats on my AIS screen. I am afraid it would compromise it as a navigational tool. I don't understand why there is a push for recreational boats to transmit. ??
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Old 20-08-2007, 17:52   #18
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Boating is a two dimensional affair and generally more data is better. However data needs to be converted to information that you can make decisions on. Drawing a circle and projecting your own course is a good step in turning data into information.

Similar arguments were made about aircraft collision avoidance. The big boys are flying under ATC control so why do they care everyone else should get out of the way. TCAS operates in a 3D environment and areas like the LA basin are a zoo of traffic.

TCAS not only plots targets but give vectors altitude and rate of altitude change. The interesting thing about TCAS is that most targets are never seen visually. It's very hard to spot an aircraft but the information allows corrective actino even without ever identifying the target visually.

AIS is similar and having it is a good thing in my book. At least the big ships can plot targets and if something looks close they can blow a warning.

I expec the technology will improve over time like TCAS did and eventually will plot vectors, prioritize targets and issue alarms.
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Old 20-08-2007, 19:20   #19
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Originally Posted by svanr
I REALLY REALLY don't want to have hundreds of recreational boats on my AIS screen. I am afraid it would compromise it as a navigational tool.
I fail to see how having less information available would make AIS a better tool?? BTW, it should be considered a collision avoidance tool, vice navigational tool. Do you not have the capability to discriminate between targets (filter by class, range, etc)? You can always turn it off when in a sea of recreational boats, but surely in the fog, it would be better to have it available to show the little guys too. Simrad also described a bunch of power boats veering at the last minute - chances are they didn't paint as well as the Evergreen behemoth.

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Old 20-08-2007, 20:08   #20
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Now picture yourself out on the high seas in heavy weather...wouldn't you want your little sailboat to show up on a big ship's AIS instead of gettting lost in the sea clutter on his radar. I'm sure the watchkeepers on the ships would rather know from 10 miles out instead of 1 mile if that faint target or small light is a sailboat or a motorboat, which they should be able to tell from the AIS display.
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Old 20-08-2007, 20:08   #21
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Now picture yourself out on the high seas in heavy weather...wouldn't you want your little sailboat to show up on a big ship's AIS instead of gettting lost in the sea clutter on his radar. I'm sure the watchkeepers on the ships would rather know from 10 miles out instead of 1 mile if that faint target or small light is a sailboat or a motorboat, which they should be able to tell from the AIS display.
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Old 20-08-2007, 23:05   #22
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Originally Posted by ssullivan
To think of why - put yourself outside of your boat and your world for a second.
That's exactly how I think of it. AIS is a system of cooperating vessels. Everybody agrees to report their data accurately, so that everybody can better avoid collisions.

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Put yourself on the bridge of a conatiner ship entering NY Harbor or San Francisco or Baltimore or some city you are familiar with. Here you are on the bridge on watch and responsible for the safety of your ship as well as for not colliding with other boats (REAL boats, not our little dinky craft we like to think are so important - me included).
You understate the responsibility of the bridge crew. They are required to avoid collisions with ALL vessels, not just BIG ones.

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Now... let's imagine every idiot in his 420 or O'day 302 (I owned one) has an AIS transponder beaming out his information as he tacks back and forth across the entrance to the harbor.

This RUINS the AIS information for the container ship - showing nothing but a swarm of meaningless data all over his screen. It doesn't help him in the least, and he will, in all actuality, ignore your data anyway if he can discern the data from real ships in the area when your little recreational transmitters are crowding up his screen.
I don't agree that it ruins anything. I don't agree that the data is meaningless.

Each point still represents a potential collision to be avoided. As I said, the ship is not permitted to run down the O'Day just because it is only 30 feet long. If the small boat is operating in a responsible manner, that fact will be clearly recognizable from the AIS display. e.g. It will be on the correct side of the channel, or even outside the channel completely (my preferred location when encountering ships).

It may even be useful. I had a ship try to call me on the radio by a different boat's name once. He heard a sailboat named Sula on the radio a few hours before, so when he saw a sailboat about where he expected to find Sula, that was who he called on the radio. He was probably sweating when I didn't answer the first couple calls, but then I called him to see if he was really looking at me. We would have had that discussion a mile further apart if an AIS machine had told him my boat name and MMSI number.

On the other hand, if the O'Day remains in the channel, the ship crew is still required to do what they can to avoid killing anybody. This really happens, though last time I read about an example, it was a Catalina, not an O'Day, and the ship saw their navigation lights, not an AIS report.

b.t.w. Of course, the bridge crew is going to ignore some of the data -- nobody ever pays equal attention to all objects in their environment. They will ignore all the fishing boats hanging out around Fort Carroll, EXCEPT for the one that is heading directly into the main channel.

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Now... if AIS class B was on a different frequency entirely and did not show up on the container ship's display, but only showed up on recreational vessels, I would be for that.
Using a different frequency is not necessary and would only increase the cost of the system. Class b AIS reports are clearly recognizable to the computer doing the processing. If you want a button to make all class b vessels disappear from your AIS display, there is no TECHNICAL reason that would make that difficult. I could see legal problems if you press that button, then run over one of them, though.
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Old 21-08-2007, 01:50   #23
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Originally Posted by Ex-Calif
[...]
AIS is similar and having it is a good thing in my book. At least the big ships can plot targets and if something looks close they can blow a warning.

I expec the technology will improve over time like TCAS did and eventually will plot vectors, prioritize targets and issue alarms.
Most AIS systems (receive-only as well as full transponder) already do all this. Typically, they will plot vectors, and prioritize/alarm based on Closest Point of Approach (CPA) and time to CPA.

I have receive-only now, and will eventually install either class-B or perhaps class-A, depending on how class-B plays out. I will assume that the big guys may very well ignore or disable class-B targets, and I will act accordingly.
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Old 11-10-2007, 22:58   #24
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If you are a yachtsman then use some common sense. Turn the transmitter off in congested waters and on in waters that are not congested. In congested waters such as in harbors, large vessels constrained by their draft have the right of way over sailboats anyway. So even if you have your transmitter on in congested waters it is not going to do you any good since you have to stay clear of vessels constrained by their draft anyways. They will know you are there but they won't be able to do a whole hell of a lot about it if you are hanging out in "their" channel.

Stay out of their channel and stay out of their way and you won't need an AIS transmitter in congested harbors. Save your transmitter for the open ocean where large vessels have the maneuvering room to avoid you.

Saying an AIS transmitter for a yacht is good or bad is missing the point. Sometimes it is good and sometimes it is bad. You just have to use some good boat sense and examine the situation to determine if turning on the transmitter has the potential to cause more problems or fewer problems. It all depends on the situation.
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Old 12-10-2007, 06:27   #25
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In congested waters such as in harbors, large vessels constrained by their draft have the right of way over sailboats anyway.
Sorry to be pedantic, David, but the US Inland Rules don't recognize vessels as "constrained by their draft." You'd be correct in saying that sailing vessels are required to not impede large vessels in narrow channels or traffic separation schemes.
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Old 12-10-2007, 06:36   #26
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I don't understand why there is a push for recreational boats to transmit. ??
Never heard there was a push...?
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Old 13-10-2007, 00:04   #27
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Sorry to be pedantic, David, but the US Inland Rules don't recognize vessels as "constrained by their draft." You'd be correct in saying that sailing vessels are required to not impede large vessels in narrow channels or traffic separation schemes.
You are correct. The bottom line meaning is still the same. Sailing vessels and vessels under 20 meters in length shall not impede a vessel that can only navigate within a narrow channel or fairway. And why is this?... because they are constrained by their draft although it does not state so.

Port captains can and do declare the waters of a port as narrow channels.

http://www.starpath.com/freeware/USvINT-NavRules.pdf

Harbor Police - San Diego Bay Narrow Channels and U.S. Coast Guard Inland Rule 9
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Old 13-10-2007, 06:21   #28
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David,

Narrow channel does not always imply there are draft constraints. San Diego is a good example, where a deep draft might collide with a jetty or the aircraft carrier tied up to it, without running aground. Anyone driving a large ship doesn't need to be told that San Diego is a narrow channel - it's self-evident. The port authority is advertising that fact to the small boat operators, in an attempt to have them not impede the large boats.
Making blanket statements like "In congested waters such as in harbors, large vessels constrained by their draft have the right of way over sailboats anyway." is misleading - it really depends on the harbor and whether or not narrow channel, tss, or special port rules apply.

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Old 13-10-2007, 18:23   #29
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David,


Making blanket statements like "In congested waters such as in harbors, large vessels constrained by their draft have the right of way over sailboats anyway." is misleading
Kevin
Not to me it isn't.

The bottom line is, with or without AIS if you are dumb enough to put your little 26 ft. trailer sailer in front of a much larger, heavier and less maneuravable craft and call "right of way" you are a fool and won't be sailing long.
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Old 13-10-2007, 19:38   #30
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Therapy,

You forgot to check my occupation. The 26 footer is a hobby - my day job is driving the much larger, heavier and less manoeuvrable craft. If you are dumb enough to not follow the rules and do stuff that is unpredictable in front of the large ships, you are a fool and won't be sailing long.

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