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Old 10-09-2013, 07:39   #1
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Why AIS?

Howdy all, been looking and have not found answer. Hope someone can help. Is AIS really needed? What percentage of boats out there actually have it? Use it? From what I get out of it, is somewhat like IFF on military vehicles. Wouldn't radar and radar reflector work just as well? We are just getting started outfitting our new (to us) boat for trip south next spring, and believe radar/reflector will be with us, so wouldn't the AIS system be somewhat redundant? Just a question that keeps coming up in my mind. Anyones thoughts? Thank, Bob
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Old 10-09-2013, 07:45   #2
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Re: Why AIS?

Depends a lot on where and how you use your boat.

At minimum I would get a combo AIS receiver and VHF, like the Standard Horizon GX2150. You won't transmit, but you'll see other contacts.

This whole thing has been debated a lot in a recent thread, but in general the adoption has been quite rapid. It's not ubiquitous, it has some short comings, and it's not (nor will it ever be) on every boat.

I find it to be a very valuable technology. It's relatively cheap, easy to set up, uses little power, and helps avoid collision.
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Old 10-09-2013, 07:59   #3
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Re: Why AIS?

Here's that recent discussion, read away

AIS: A Creepy Experience.
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Old 10-09-2013, 08:10   #4
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Re: Why AIS?

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Originally Posted by BobnCamie View Post
Howdy all, been looking and have not found answer. Hope someone can help. Is AIS really needed? What percentage of boats out there actually have it? Use it? From what I get out of it, is somewhat like IFF on military vehicles. Wouldn't radar and radar reflector work just as well? We are just getting started outfitting our new (to us) boat for trip south next spring, and believe radar/reflector will be with us, so wouldn't the AIS system be somewhat redundant? Just a question that keeps coming up in my mind. Anyones thoughts? Thank, Bob
Bob, AIS is another tool in the arsenal to keep you safe. It's nice to see a large vessel 15 miles away, and have his course, speed, and CPA info right at hand.

Here in the Puget Sound, almost all commercial vessels and a high number of pleasure craft are equipped with AIS. We currently have a SH 2150 radio, and will soon be installing an AIS transponder.
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Old 10-09-2013, 08:12   #5
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Re: Why AIS?

I presume if you are taking your Four Winns or Oday South, then you will be in the ICW most of the way.

There, AIS will be far more useful than radar, as you will be able to see large commercial boats around bends, etc.

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Old 10-09-2013, 08:32   #6
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Re: Why AIS?

I've used an AIS receiver for four years of cruising, including one cruise to Maine and back, which featured several days and nights of thick fog in high traffic areas (such as Sandy Hook).

I think AIS is invaluable. Although I'm an experienced radar user, I've decided not to install radar on my boat, even though I've had the money and an opportunity to buy a great unit at a great price from a friend. (I don't normally cruise in New England, and I might revisit this decision if I went back up there.)

I was helping a pal deliver his (new to him) boat a couple of weeks ago. We were experimenting with the radar on a crystal clear day, learning which buttons to push to get the display to synch with the chart, etc. We were in an area rather congested with small craft, the kind of craft you wouldn't expect to have an AIS transceiver, and thus the kind of craft you'd hope to see on radar in low visibility. This kind of traffic is, I think, one of the only remaining reasons to own a radar on a small boat.

I was experimenting with great interest, trying to decide if I should install radar on my own boat. My conclusions: by the time I could clearly see small craft on the radar, at a level of zoom that gave me clear navigation information, I would have seen or heard the small craft anyway in most any level of fog. If the fog were truly so dense you couldn't see much beyond the bow, we would have been going dead slow anyway, sounding fog signals, and I don't think the radar would have been much additional help.

Lots of people will disagree, surely, but I'm sticking with my decision to rely on AIS, a chartplotter, slow speed, fog signals, and security calls on the VHF in fog situations. For what it's worth.
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Old 10-09-2013, 08:41   #7
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Re: Why AIS?

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Originally Posted by BobnCamie View Post
Howdy all, been looking and have not found answer. Hope someone can help. Is AIS really needed? What percentage of boats out there actually have it? Use it? From what I get out of it, is somewhat like IFF on military vehicles. Wouldn't radar and radar reflector work just as well? We are just getting started outfitting our new (to us) boat for trip south next spring, and believe radar/reflector will be with us, so wouldn't the AIS system be somewhat redundant? Just a question that keeps coming up in my mind. Anyones thoughts? Thank, Bob

Needed? No. Useful, probably yes, depending on your cruising grounds.

Radar better, for us. Especially at night or in the fog. Radar reflector good, when it works (I understand they don't always).

AIS redundant? Yes, and not exactly Would you benefit by being able to call a commercial ship by name and arrange safe passage? If so, AIS receive can help facilitate that "by name" thing. Would you benefit be having some other vessel call you and arrange safe passage? If so, AIS transmit can help facilitate that "by name" thing.

Otherwise your hailing choice is something like "big northbound ship passing lat/long..." or maybe "white boat in the Chesapeake near Annapolis..." -- with varying results. Or maybe somebody will call you "power cruiser heading southbound in the ICW..." -- and that may or may not mean you.

Redundancy isn't a bad thing, depending on your wallet. We have two each GPSs, depth finders, and VHF radios (plus a handheld). And radar. But we also have an AIS transceiver, and find it useful... even though most small craft around here don't have a transmitter.

When it's helpful, it's often really helpful, usually when we're trolling near one of the channels commonly used by commercial shipping or tugs/barges... given that our trolling rig is a bit cumbersome, can't turn on a dime, lots of other small boat traffic in the same place and hindering quick course corrections, etc.

-Chris
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Old 10-09-2013, 10:28   #8
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Re: Why AIS?

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[...] I was experimenting with great interest, trying to decide if I should install radar on my own boat. My conclusions: by the time I could clearly see small craft on the radar, at a level of zoom that gave me clear navigation information, I would have seen or heard the small craft anyway in most any level of fog. If the fog were truly so dense you couldn't see much beyond the bow, we would have been going dead slow anyway, sounding fog signals, and I don't think the radar would have been much additional help. [...]
I'm a huge fan of AIS, but I have to jump in and defend radar here. In heavy fog, you may be going dead slow, but the other guys may be running full tilt. Radar can definitely help in that situation.

There must be a few dozen discussions of AIS here on Cruisers Forum.

For what it's worth, my sailboat has a transponder, and the little powerboat has an AIS receiver. I will be installing a transponder in that, too. It gets foggy here! But I like tech stuff. I'm not going to claim that AIS is absolutely necessary for the cruiser, but it is very useful.
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Old 10-09-2013, 11:42   #9
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Re: Why AIS?

AIS is worth it just for the stress reduction alone. A target shows up and instantly you have the closest point of approach and time to the closest point of approach, CPA/TCPA. In a second you can decide if the target is an issue for you or not. No second guessing the track of the target. For a new electronics fit out, it makes no sense not to at least have RX AIS.
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Old 10-09-2013, 12:39   #10
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Re: Why AIS?

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I'm a huge fan of AIS, but I have to jump in and defend radar here. In heavy fog, you may be going dead slow, but the other guys may be running full tilt. Radar can definitely help in that situation.
Yeh, I've seen that. The other guy's radar was turning as he came barreling out of the fog, fifty yards away on a dead collision course. When he saw me with his eyes, he swerved.

I guess this isn't off topic, and it's certainly been covered in other threads, but most recreational boaters can't operate radar well enough to avoid a collision. Another STRONG argument for AIS. Combined with a good chart plotter, it will let you know- graphically- if a collision is imminent.
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Old 11-09-2013, 10:56   #11
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Re: Why AIS?

Post #5 Colemj, just convinced me. I wasnt aware (or had not thought about) AIS showing a vessel that radar would be invisible to, such as around the bend. I also agree with the other comment, that most pleasure boat operators dont use radar enough to know how to adjust it properly. It takes a lot of practice in clear weather to make you reasonably good when you are in the soup. Learning something new everyday. _____Grant.
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Old 11-09-2013, 11:14   #12
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Re: Why AIS?

Living on the colder west coast where fog is a common problem I have been using radars since the 80s. I hvae avoided many in fog collisions over the years. I look at computer generated AIS but find it rather lacking in this area. The big vessels, mostly commercial, seem to have it, but the big number of smaller crafts which travel at higher speeds don't. I believe it is a good addition but we should be aware of how easily complacancy can set in with high tech equipment. Just because we don't see it on the screen doesn't mean it's not coming straight at you. I don't think I would consider it a replacement for radar and would choose radar first every time if there was only one choice. Buoys and other such devices are not sporting AIS, yet.
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Old 11-09-2013, 11:21   #13
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Re: Why AIS?

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Living on the colder west coast where fog is a common problem I have been using radars since the 80s. I hvae avoided many in fog collisions over the years. I look at computer generated AIS but find it rather lacking in this area. The big vessels, mostly commercial, seem to have it, but the big number of smaller crafts which travel at higher speeds don't. I believe it is a good addition but we should be aware of how easily complacancy can set in with high tech equipment. Just because we don't see it on the screen doesn't mean it's not coming straight at you. I don't think I would consider it a replacement for radar and would choose radar first every time if there was only one choice. Buoys and other such devices are not sporting AIS, yet.

If you mean a web viewer something like marinetraffic.com... they rely on receive-and-forward stations scattered around... that's receive VHF and forward to the web... mostly volunteer, I think... so reception and subsequent display can be skewed by that.

Where we are, the nearest station to the north often can't see us. The nearest station to the south can only sometimes see us, and I think our local buildings block the signals to a certain extent. (Although I see we're displaying now (from that northward station K3ARS), only one of the nearby Fleming fleet is on the chart... and usually there are several with transmitters.)

None of that negates your point, of course...

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Old 11-09-2013, 11:33   #14
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Re: Why AIS?

BIg ships are required to have AIS above 300 tons I believe BUT many I understand do not have the ability to overlay AIS contacts on their chartplotters or radars, . so it is not safe IMO to rely on your own AIS transmission making you 'visible' to others, large or small. Big ships can and do turn off their AIS transmissions for various reasons (Llike in a piracy prone area or because they are military and want to remain in stealth mode ) and boats under 300tons not obliged to have AIS still hurt when they hit you

WE are refitting our new to us boat with all new electronics and yes AIS (transmit and receive) is included in the new Garmin NMEA 2000 network with the ability to overlay AIS and radar targets on the chart plotter display. We have Had radars on various boats for 20 years or more of sailing in foggy UK/EU waters and would not be without it now even though nowadays our cruising is in the Atlantic ICW and outside to the islands where fogs are less frequent.
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Old 11-09-2013, 12:47   #15
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Re: Why AIS?

Bob

As stated above, AIS is another tool in your bags of safe sailing...

We have an AIS Class B unit on our boat and used it from San Francisco to Southwest Florida.

It was effective and we found it very useful, especially around heavily trafficked ports and the Panama Canal.

You will also normally see AIS targets before RADAR depending on the height of the antennas and like previously stated it was a blessing when we used to cruise the Sacramento Delta and could see barges coming down river from around a curve.

The only problem with AIS is not everyone has it.... Which makes Radar more valuable for the time being. Also radar will do more things than just aid you in fog or darkness... It will help determine if you anchor is dragging, determine closest points of approach and of course relative speeds of other vessels.

If I had a choice of only one I would definitely purchase a RADAR first and then augment it with AIS when I had the money.
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