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Old 01-11-2009, 10:05   #46
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Bill,

Get a ride on a boat with AIS and try it out, especially offshore before you knock it. The range and accuracy of AIS is far better than the eyeball or radar. If you don't have one, you are throwing away the ability to easily get the speed, course, CPA and name of a ship before your methods even know it exists. All for under $500 and 200 milliamps of power consumption. Its far less stressful to make a 5 degree course correction when the ship is 20 miles away.

Of course, you probably don't use a GPS either....
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Old 01-11-2009, 10:20   #47
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Warships do occasionally transmit on AIS, even while at sea, but for the most part they are silent.

Bill, you seem to think all us AIS users are sitting below at the navstation, staring at the AIS/chartplotter display, and steering by autopilot and waypoint.

By the way, where I sail, floating junk hardly ever shows up on the radar -- the swells are too big for that. That's one reason we always have a crew topsides with eyeballs and binoculars and hand-bearing compass at the ready.

Again, stupid people will do stupid things. Don't be stupid!
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Old 01-11-2009, 10:36   #48
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Originally Posted by btrayfors View Post
1. unnecessary;
That's what they said about GPS
Quote:
2. another complication;
That's what they said about GPS
Quote:
3. not synoptic and thus potentially very misleading
That's what they said about GPS
Quote:
4. downright dangerous as many inexperienced sailors will be lulled [...]
That's what they said about GPS

Quote:
That's the whole point: warships are very unlikely to show up on your AIS display.
When warships shut down their AIS, civilian radar etc. it becomes their responsibility to compensate with extra/other measures for safe navigation. You should not be worried about them colliding with you so much.

Quote:
Most of these WILL show up on radar, though, [...]
Again, AIS is no replacement for radar. Vessels that are required to have AIS must also keep their radar. Yachts that do away with radar when they install AIS, or install AIS before radar, are going to be a hazard to navigation anyway, no matter how they are equipped.

Quote:
and virtually all of them will show up on your Mark I eyeballs, providing you are keeping a sharp watch and, at night, haven't spoiled your night vision staring at mostly irrelevant screen data.
If you can see fishing nets, pots, logs, trees, containers, etc. with your eyeballs at night you must be an Android ;-)

But, who said AIS is a replacement for keeping a lookout? It is, in fact meant to complement lookout for situations that no human being can handle: ships to far away to see if there's risk of collision (complementing ARPA but more accurate), ships behind a land-feature but on collision course (no replacement aid available), so many ships that our brain can't cope etc.

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-- STAY OUT OF THEIR WAY. Don't waste time trying to contact them.
When the ship is on a steady course and speed and at enough distance: yes. But asking intentions when their maneuvers aren't clear is the norm and an important safety procedure. They might not anticipate your course change, making things worse. When you have an AIS transponder yourself and they maneuver into a collision alarm, they even expect your call. For passing starboard to starboard a call is also expected.

cheers,
Nick.
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Old 01-11-2009, 12:58   #49
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btrayfor - Stop that you are stealing every reason why I also do not have AIS onboard.
- - Actually, I did purchase a unit when they first came out but have never installed it for exactly the reasons you cite. It will give the false assurance that you will pick up "all" vessels that might cause you harm. That is enormously wrong! It will only pick up vessels "required" to have it and actually do have it turned on. Example: Naval/Customs/Immigration/police vessels do not turn it on, if they even have it. Many commercial vessels will turn it off (especially 3rd world vessels) unless they are operating near or into a country that requires it.
- - Anything that takes my attention away from visual searching or radar searching is extremely hazardous to your vessel's or your longevity IMHO. Example: Jessica Watson.
- - Out here in the oceans and seas where 3rd world vessels are common you will find very little adherence to COLREGs and the lighting/marking rules. At night unlit vessels are everywhere including tugs and barges, freighters and pirates. Keeping a vigilant visual and radar watch is the only way to protect yourself.
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Old 01-11-2009, 14:01   #50
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Osirissail has a very good point. In the Eastern Carribean I have observed that at least 25% of shipping do not display running lights. At first I was flabergasted but now I consider it a part of the norm. On a moonlit night I keep a good watch, other times I turn on my radar from standby to run ever 20 minutes.

Talking to another cruiser who recently arrived from the US. he said that the only ships that consistently displayed AIS were cruise ships. We doubted that most of the coasters had AIS. Also I rarely see their radar antennas in action.

Eventually, when I return to an area that uses it, and the cost comes down, I'll purchase one. I find that $800 plus for a transceiver a lot of money and the cheaper receivers only do half the job, since other vessels can't see you.
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Old 01-11-2009, 14:29   #51
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Re warships and AIS. I spent an interesting evening with a rather nice Officer in the Royal Navy. In the course of conversation I complained that the navy around the British Isles never seems to be broadcasting AIS information. He agreed but pointed out that although I may not see them on AIS, they have it on receive all the time and know exactly where each vessel is. They use it as an adjunct to and integrated with ARPA.
I usually see the navy on my radar but earlier this year I was about 3 miles off one of the new frigates, It was very calm and I could very clearly see it with the 'mark one eyeball' but on my radar she showed as sea clutter, even radar is not infallible, even in the best of conditions.
No 'aid to navigation' is an excuse not to keep a good look out. AIS is just another tool, that used properly helps to clarify a lot of data. During a recent passage down to Gibraltar, in 8' to 10' seas, I was quite happy to have the extra information, especially at night.

Paige
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Old 01-11-2009, 16:05   #52
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Osirissail has a very good point. In the Eastern Carribean I have observed that at least 25% of shipping do not display running lights.
Everything 300 tonnes or more has it plus all passenger carrying boats. Even tugs and pilotboats show up on AIS (in the Caribbean).

cheers,
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Old 01-11-2009, 16:58   #53
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It will give the false assurance that you will pick up "all" vessels that might cause you harm.
If this is true, then you should not install that AIS unit. My guess, however, is that a few hours or days of practice in a busy harbor will help you shed that false sense of assurance.

Or don't install it. Honestly, no one will think any less of you.
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Old 31-01-2010, 03:09   #54
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Gentlemen, fascinating. As a yachtie, a merchant seaman and a VTS operator. I've read with fascination every single post in this thread. The level of knowledge and ignorance on the subject is brilliant. I'm not going to throw my hat into the arena as the thread has already taken on a life of its own.
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Old 31-01-2010, 04:46   #55
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Ianhef,
I'm glad someone is working on AIS and how to best use it. Its not perfect, as evidenced by Jessica Watson's infamous encounter with the ship off Brisbane. As both Jessica and the ship involved had active AIS, its very educational to study the incident. I'm sure you have access to more information, and I have a few questions.

What kind of transponder was Jessica using--A or B??

I'm pretty sure she was asleep/untrained/inexperienced in the use of her AIS, but what about the watch on the ship? Why didn't they pick up her transponder, realize a collision was possible, and take corrective action long before they got a visual fix on her??

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Old 31-01-2010, 06:50   #56
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As far as I'm aware Jessica did not have AIS on her trip down to Sydney, if I'm wrong please someone correct me. Her Class B AIS was only fitted on arrival in Sydney.

I'm not in a position to comment on Jessicas actions prior to the collision but if you google it I'm sure you will find some interesting reports, suffice to say I'm sure she is a much wiser sailor today.
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Old 31-01-2010, 08:06   #57
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Originally Posted by fishwife View Post
I usually see the navy on my radar but earlier this year I was about 3 miles off one of the new frigates, It was very calm and I could very clearly see it with the 'mark one eyeball' but on my radar she showed as sea clutter, even radar is not infallible, even in the best of conditions.
Paige
I think that's the way the newer warships are designed. Kind of like the stealth aircraft, they confuse the radar with angular planes and special surface finishes. Rather clever stuff - I wonder how long it'll take the smugglers to catch up.
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Old 31-01-2010, 17:28   #58
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It will give the false assurance that you will pick up "all" vessels that might cause you harm.
Things only give you "false assurances" if you let them, AIS is merely another aid to naviagtion, but its a cheap and excellant one, and sailing up th eenglish channel, I wouldnt want to be without it. ( and radar and mkI eyeball and anything else I could use/find). As to if its "synoptic" or not , who cares.
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Old 31-01-2010, 18:30   #59
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According to the preliminary report http://yachtpals.com/files/news/jess...ion-report.pdf Jessica had a NAIS-300 class B transponder on, and the report has several screenshots from some land-based AIS tracker before and during the collision where both vessels are shown.

My merchant marine friends love their AIS systems, and mine would have had CPA alarms going off for an hour before the collision.
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Old 31-01-2010, 18:54   #60
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Really!

Hmmm, let's see. Two vessels on a collision course in good weather. At night. Both travelling at fairly slow speeds.

Both are equipped with radar AND with Class B AIS. Both AIS units working, apparently, because shore stations monitored the progress of both vessels.

Collision, just before 2AM.

Can someone explain how, exactly, AIS (or radar, for that matter) helped to avoid a collision in this instance?

While the young lady "failed to detect [the oncoming ship]" which was pretty close off her starboard bow, was that because she only consulted her electronics? Spoiled her night vision peering at screens? Failed to maintain a proper lookout??

IMHO, and recognizing that we don't have all the facts of the case, this might be put down as just one more case of an instrument-assisted collision/grounding/calamity.

Did the instruments CAUSE it? Of course not. But they could well have played a contributory role by instilling a (manifestly incorrect) sense of safety and/or contributing to the failure of the skipper to detect an oncoming ship -- which was closeby -- using the Mark I eyeball. IMHO.

So, by all means carry radar and AIS and GPS and all that. Set your guard zones and CPA alarms, and anchor radius alarms and all that. Good idea.

JUST DON'T DEPEND ON THEM 100%.

Bill
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