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Old 04-01-2012, 20:16   #61
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Re: AIS experience offshore?

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Originally Posted by callmecrazy View Post
You have online AIS buddies?
This is more than enough reason for me to not transmit AIS. Too many strangers watching...
There are ad-hoc networked AIS receivers all over the world (look at Marinetraffic.com or AisHub.net for examples). There are private for-profit AIS monitoring networks. There are government-run AIS monitoring networks. There are groups of AIS-enthusiasts in every country (Shipplotter). If you want to be anonymous do not transmit AIS.

I'm not personally worried about this, but if it starts to bug me I can always flip the "stealth" switch.
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Old 04-01-2012, 21:22   #62
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Re: AIS experience offshore?

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What was meant that inn terms of benefit against cost it ranks above radar and I'd agree. On a budget conscious fit out I'd pay for it before radar.

Dave
AIS is in the category of collision avoidance tools. AIS is blind to 99% of the vessels on the water. Since radar shows all of the vessels on the water, 100 times more than AIS, and only costs 10-12 times more, I'll buy radar first. AIS is a great tool, a great supplement to radar, but not the sole tool in low visibility situations. And, of course, it must be a transceiver so those AIS equipped vessels can see you.
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Old 04-01-2012, 21:33   #63
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Re: AIS experience offshore?

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Originally Posted by Paul Elliott View Post
There are ad-hoc networked AIS receivers all over the world (look at Marinetraffic.com or AisHub.net for examples). There are private for-profit AIS monitoring networks. There are government-run AIS monitoring networks. There are groups of AIS-enthusiasts in every country (Shipplotter). If you want to be anonymous do not transmit AIS.

I'm not personally worried about this, but if it starts to bug me I can always flip the "stealth" switch.
Yes, I understood the 'visibility' of AIS. I just didn't realize there were individuals who would watch boats movements making assumptions about the activity to the point that they would actually take an investigation into their own hands. And then chat online about it with their enthusiastic buddies...

I don't care about complete anonymity, this is just kinda creepy...
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Old 04-01-2012, 22:53   #64
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Re: AIS experience offshore?

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Originally Posted by callmecrazy View Post
Yes, I understood the 'visibility' of AIS. I just didn't realize there were individuals who would watch boats movements making assumptions about the activity to the point that they would actually take an investigation into their own hands. And then chat online about it with their enthusiastic buddies...

I don't care about complete anonymity, this is just kinda creepy...
Well, I suppose that's one way of looking at it.

In my case this has involved arrivals of publicly-announced vessels, such as Queen Mary 2, the tall ship Bounty, the Polynesian ocean-crossing canoes, the Maltese Falcon, and friends who have asked me to track their AIS-equipped boats. My occasional military vessel reports have always been delayed for a week or two, and these comings and goings are the subject of newspaper articles. What is interesting about the Navy ship AIS sightings is that they are transmitting in the first place. If they wanted anonymity they wouldn't be transmitting.

"Taking an investigation into their own hands"??? What are you talking about?

Go ahead and call it creepy, but I just don't see it.
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Old 04-01-2012, 23:35   #65
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Re: AIS experience offshore?

IT's No different than 'trainspotting'

Just as an intellectual exercise I wanted to create a program that logged all AIS 'hits' and then could compare when/where I'd encountered ships worldwide.

I never did it because I haven't actually gone anywhere yet, and didn't really have time, but I figure I will do it eventually if when I ever actually cast off.
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Old 04-01-2012, 23:53   #66
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Re: AIS experience offshore?

And some take photos while monitoring you....

I was on the bridge with the pilot this day, transiting the Tamar River to Bell Bay when someone took this pic, probably a Ruskie spy ....

: Ship Photos

As xymotic say's, It's all harmless fun like trainspotting, the enthusiasts just use Live Ships Map - AIS - Vessel Traffic and Positions ,or some other outfit, to see whats in port or arriving so they can nip down for a quick photo session.....

Saves getting off their bum and going for a look i guess....
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Old 05-01-2012, 01:01   #67
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Re: AIS experience offshore?

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And some take photos while monitoring you....

I was on the bridge with the pilot this day, transiting the Tamar River to Bell Bay when someone took this pic, probably a Ruskie spy ....

: Ship Photos

As xymotic say's, It's all harmless fun like trainspotting, the enthusiasts just use Live Ships Map - AIS - Vessel Traffic and Positions ,or some other outfit, to see whats in port or arriving so they can nip down for a quick photo session.....

Saves getting off their bum and going for a look i guess....
Lol, I think trainspotting is kinda creepy too
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Old 05-01-2012, 03:13   #68
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Re: AIS experience offshore?

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AIS is in the category of collision avoidance tools. AIS is blind to 99% of the vessels on the water. Since radar shows all of the vessels on the water, 100 times more than AIS, and only costs 10-12 times more, I'll buy radar first. AIS is a great tool, a great supplement to radar, but not the sole tool in low visibility situations. And, of course, it must be a transceiver so those AIS equipped vessels can see you.
Your conclusion might apply if you were in a small boat harbor channel in the fog, but if you have ever been offshore (see thread title) you would know that over 90% of the vessels you will encounter are transmitting AIS data.

Not only does AIS cost less, it draws less than 10% of the power, is more accurate for collision avoidance, works in heavy rain and around blind corners, doesn't give false alarms like radar guard functions, and gives you the name of the vessel so you can contact them. An AIS receiver is hands down a better bang for the buck.

In my experience, even a one-channel receiver gives you 80% of the value of AIS. Although I have a transponder, I will pick up the ship's Class A signal before it picks up my weaker Class B signal and will make a course correction to keep the CPA over 1 mile before the ship is aware of my presence. I would rather have the ship maintain its course than create confusion on the bridge.
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Old 05-01-2012, 03:28   #69
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I would rather have the ship maintain its course than create confusion on the bridge.
If all sailors thought and responded like this, The seas would be safer for all of us. "Thumb"

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Old 05-01-2012, 04:01   #70
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pirate Re: AIS experience offshore?

I agree... but thats what responsible cruisers should be capable of with or without AIS...
My general skepticism is based on my 1st experience with it last year when I delivered a Vancouver 34 with it fitted... crossing the Channel the shipping marched across the screen... keeping the owner wound up as we crossed... when we reached the Biscay big fishing boats would appear.. then disappear... even when we could see them the image would vanish... a few ships/coasters without anything...
So no... today I would not go and buy one... as I said... when there's the technology to produce an economical H/H that Joe fisherman can carry I'll remain yet another of the 'Great Unseen'...
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Old 05-01-2012, 04:48   #71
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Re: AIS experience offshore?

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We instaled a Watchmate 850 last year. Class B transponder and A B reciever.
This unit also has many filtering options so you can have it ignore all anchored vessels and all vessels headed away or not crossing withing your defined circle. Nice in very busy harbors.
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The Watchman 850 is on my wish list. I looked at it at the boat show">Annapolis Boat Show. I liked what I saw. It had a weather menu button. I asked what that was. Fellow said it was for Sweden. It seems they send weather data there on AIS too. I understand there are some experiments in the U.S. (Tampa area) with sending weather buoy info on AIS. Though I guess all bouys could technically be fitting with some type of low power AIS transmitter in the future. Sounds like a good idea to me.
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Old 05-01-2012, 04:49   #72
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Re: AIS experience offshore?

AIS Greenhorn here, so sorry for the basic questions.

In terms of alarms. For those of you that have both Radar and AIS, do the contact alarms go off at the same time? Which has proven to be more accurate in terms of false positives? Could you walk through your setup using both or your decision to use one over the other in open ocean.

Thanks a ton!
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Old 05-01-2012, 06:28   #73
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Re: AIS experience offshore?

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Your conclusion might apply if you were in a small boat harbor channel in the fog, but if you have ever been offshore (see thread title) you would know that over 90% of the vessels you will encounter are transmitting AIS data.

Not only does AIS cost less, it draws less than 10% of the power, is more accurate for collision avoidance, works in heavy rain and around blind corners, doesn't give false alarms like radar guard functions, and gives you the name of the vessel so you can contact them. An AIS receiver is hands down a better bang for the buck.

In my experience, even a one-channel receiver gives you 80% of the value of AIS. Although I have a transponder, I will pick up the ship's Class A signal before it picks up my weaker Class B signal and will make a course correction to keep the CPA over 1 mile before the ship is aware of my presence. I would rather have the ship maintain its course than create confusion on the bridge.
I guess offshore is a variable definition. 10 miles? 50 miles? 200 miles? Major crossing? Yes, I have experience offshore doing all of it.

The claim of 90% of the vessels offshore are transmitting AIS brings up the question "How do you know?". Have you ever transited commercial fishing areas at night? When you see 6 sets of nav lights at night, do you assume there are only 6 other vessels? I make collision avoidance my responsibility, I don't put faith in others sending AIS information, nor running nav lights. For the sake of discussion, let's accept 90% as the number, that leaves 10% of the vessels you can't see. You are comfortable with that?

An AIS transceiver is a wonderful tool, I have one. But it's not a replacement for radar. Until AIS shows 100% of the vessels, which will be never, radar should be the first choice of tool in low visibility situations. Relying on AIS as the only tool in low visibility situations will kill people.

Radar should not be compared with AIS any more than comparing your dinghy with your life-raft.
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Old 05-01-2012, 07:00   #74
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Re: AIS experience offshore?

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Radar should not be compared with AIS any more than comparing your dinghy with your life-raft.
The only comparison made, and the one you seem wound up on, is the cost/benefit ratio (or bang/buck). This is an opinion, of course, and one everyone makes for all types of gear on board. The denominator is fixed, but the enumerator is a personal value judgement. You evaluate this equation differently, which is perfectly acceptable - as is anyone else's evaluation.

Frankly, I don't have any other piece of equipment on board that gives me so much information and trouble-free operation that costs less than $200. Our iPod costs more than the AIS. So I rate the bang/buck highly. Higher than the radar because the radar is about the most expensive piece of equipment we have, so the "buck" denominator in that equation is very high.

While purely statistically, 99% of the vessels out there do not have AIS, this statistic does not tell the story of passagemaking. 100% of commercial traffic has AIS, so you are left with smaller fishing boats and recreational boating. I'm not too worried about recreational boats because they are small and moving at 4-7kts - I see them well before they are a problem and can avoid one within a hundred feet with a 10 second turn of the wheel (it never comes to this of course - I'm just making an example). So the smaller fishing boats are the problem. Fortunately, they are almost all coastal and most of them lit up with floodlights.

Here is a good example of where AIS beats radar: Recently, we were entering Colon Panama at night in heavy weather. There is a breakwall with a relatively small opening - just large enough for two container ships to pass through. At any given time there are 30-50 container ships coming or going through the breakwall, anchored outside, stopped but not anchored outside, anchored inside, stopped but not anchored inside, passing by outside, passing by inside, turning in slow circles waiting outside, turning in slow circles waiting inside. The breakwall is high enough that one cannot see over it.

So radar is useless for the ships inside the breakwall, and close to useless for those outside unless you have a high-end set and a dedicated operator to keep a constantly updated radar plot.

A simple single glance at the AIS allowed us to see what path we should take to go in, which ships we needed to change course to avoid and, most important, when the opportunity existed to enter the breakwater without fear of meeting a moving ship with only 100' to make a correction to avoid being run down. The AIS paid for itself on this last point alone.

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Old 05-01-2012, 08:42   #75
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AIS is in the category of collision avoidance tools. AIS is blind to 99% of the vessels on the water. Since radar shows all of the vessels on the water, 100 times more than AIS, and only costs 10-12 times more, I'll buy radar first. AIS is a great tool, a great supplement to radar, but not the sole tool in low visibility situations. And, of course, it must be a transceiver so those AIS equipped vessels can see you.
This is an over simplification of AIS firstly it's fitted to all the stuff most people are scared of. , ie big ships. That's certainly way more then 1%. In fact where I sail it's more like 80% of vessels. In addition these tend to be the fastest on the water. Your radar will not make ships avoid you AIS transponders will.

Equally small boat , in fact any size radar, does not see 100 % of things out there it misses lots too

More and more aids to navigation are also programmed to show up on AIS. Around me all the major nav aids have AiS.

AIS is not a simple supplement to radar. It is a collision avoidance, situational awareness tool in its own right.

If I was trying to make my electronics budget stretch and I had to make priorities, AiS would be up there with VHFs and depth sounders and well before costly radar.
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