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Old 29-07-2017, 10:30   #1
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How necessary is AIS?

Planning to cruise Marathon to Daytona Beach. Thinking offshore because bridges on the ICW are a pain. Sailing most of the way. Staying close off shore saves miles but going out another 20 miles or so adds 2-3 kts to boat speed. However crossing commercial routes Miami, Port Everglades, etc make me concerned about commercial traffic. Do I really need to add an AIS receiver or just maintain focus particularly near ports? I figure that at 20-30 kt freighter speeds I will not have a lot of time to get clear.
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Old 29-07-2017, 10:38   #2
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Re: How necessary is AIS?

If you end up installing an AIS unit, you're going to be surprised by how many boats and ships, especially large fishing boats don't use it or don't turn their's on.

The bottom line.... don't count on AIS accuracy.
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Old 29-07-2017, 10:41   #3
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Re: How necessary is AIS?

No, you don't *NEED* an AIS receiver. People have been sailing without AIS among ships for a very long time.

But it is a very nice thing to have. Virtually all people who have installed an AIS receiver are happy that they did so. Many of them installed or later upgraded to AIS transponders (I have a transponder), but if you are strapped for cash a receive-only system gives you a lot of bang for your buck.

There are many ways to go about this, and these days the simplest option may be to look into the Standard Horizon or Garmin combo VHF/AIS units. They aren't particularly expensive, and you can usually plug them into a chartplotter or computer if you want a better display than the VHF unit provides.

Do some searching here -- there are plenty of discussions on this topic. Do be aware that the field is changing quickly, with newer / better / different products being introduced all the time.
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Old 29-07-2017, 10:48   #4
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Re: How necessary is AIS?

Quote:
Originally Posted by Kenomac View Post
If you end up installing an AIS unit, you're going to be surprised by how many boats and ships, especially large fishing boats don't use it or don't turn their's on.

The bottom line.... don't count on AIS accuracy.
Of course.

But in the area where Dave22q will be sailing, virtually all *ships* are mandated to carry AIS and they will be transmitting. Smaller vessels, tugboats, ferries, fishing boats, rowboats, floating debris, etc, may not have AIS. Navy ships seldom transmit AIS. Coast Guard ships usually do.
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Old 29-07-2017, 11:10   #5
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Re: How necessary is AIS?

Your boat isn't required to have AIS and as posted above, people did without AIS for centuries. So you don't "need" AIS.

On the other hand, AIS receive only can be had for under $200 and would be a nice thing to have if you are around commercial shipping.

I have seen the argument that receive only AIS is a waste of money (I don't agree) and that you should have a full transmit and receive capability.

It's up to you but I don't think the captain of that ocean going tanker really cares a whole lot about your (or my) little recreational boat. I wouldn't expect it to alter course because of my boat, I would be altering course to avoid it.
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Old 29-07-2017, 11:17   #6
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Re: How necessary is AIS?

While AIS receivers can be bought for around $200, that won't be the only costs. You'll need another antenna or a splitter for the AIS receiver. You'll also need to have a display mechanism unless your chart plotter will serve. The combined VHF/AIS units aren't much more expensive than just the AIS receiver and are a lot more convenient to install.
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Old 29-07-2017, 11:49   #7
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Re: How necessary is AIS?

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Originally Posted by rwidman View Post
Your boat isn't required to have AIS and as posted above, people did without AIS for centuries. So you don't "need" AIS.

On the other hand, AIS receive only can be had for under $200 and would be a nice thing to have if you are around commercial shipping.

I have seen the argument that receive only AIS is a waste of money (I don't agree) and that you should have a full transmit and receive capability.

It's up to you but I don't think the captain of that ocean going tanker really cares a whole lot about your (or my) little recreational boat. I wouldn't expect it to alter course because of my boat, I would be altering course to avoid it.
WE have a transponder and we're very happy we do. A transponder can be had for about $400 if you shop around.

Re: not expecting an ocean going tanker to respect the Colregs and give way - We've had a multitude of freighters and tankers give way for - including Emma Mærsk the second largest ship in the world. We can see them changing course 10 nm out. Some we've called on the radio because we're showing a CPA of only a few hundred meters - without fail, all those ships have said - no problem - we'll go right behind you - and they did

Don't think you need AIS - look at these pics of Zig Zago in Porto - the crew survived but the boat was run down by a big freighter in dense fog. Had they had AIS - this would not have happened
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Old 29-07-2017, 11:59   #8
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Re: How necessary is AIS?

Wow, the things that go bump in the night.
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Old 29-07-2017, 12:12   #9
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Re: How necessary is AIS?

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Wow, the things that go bump in the night.
I can't even imagine being on board must have scared the bejeezes out of them
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Old 29-07-2017, 12:45   #10
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Re: How necessary is AIS?

Again, people have run boat without AIS for centuries.

What is hard for me to understand is people saying one must have AIS on board to be safe but at the same time, people are discussing running their boats singlehanded and sleeping while underway. I personally think it's safer to not run a boat while asleep than to go without AIS but remain awake and on lookout at all times.

We all make our choices but that doesn't mean that your choice is the best choice for someone else.
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Old 29-07-2017, 13:00   #11
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How necessary is AIS?

This gets debated every few weeks here. Plenty of threads to read.

GPS wasn't around 100 years ago either. But it's really useful nowadays. Same with AIS. Don't believe the snarky folks who say big ships don't care about little boats. The vast majority of ships captains care about your small boat. Are there big ships driven by idiots? Yes. But the vast majority of captains will appreciate your AIS transponder. They appreciate more that you learn and follow all Colregs.
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Old 29-07-2017, 13:59   #12
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Re: How necessary is AIS?

I recently sailed from Norfolk to Newfoundland, mostly at 100 miles or more offshore and in dense fog at times. Even on clear nights, The AIS targets or contacts shown on the chartplotter were visible on the AIS display long before they were visible as Ships lights, and some were never seen as lights. Knowing they were there, and seeing their course, speed, and the CPA (closest point of approach) made watch keeping more effective, and gave the captain and crew a better sense of what was out there in the dark or fog. We even passed the Queen Mary 2 out of Halifax, and as I recall, she was making 22 knots. It convinced me of the value of AIS even for relatively low traffic routes or areas or offshore passages.

It is not a silver bullet, but like RADAR in fog conditions, it can add to your situational awareness, and that to your safety, and peace of mind.

Of course every location and skipper is different. Opinions too.
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Old 29-07-2017, 15:35   #13
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Re: How necessary is AIS?

Correct, AIS needs to be displayed on a plotter with the data to be useful.

If one has a PC and buys an AIS receiver with an USB connection, OpenCpn will display AIS data including CPA. OpenCpn is a free download which runs on Windows, Mac, etc. The required charts are a free download from NOAA charts.

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Old 29-07-2017, 17:09   #14
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Re: How necessary is AIS?

Daytime near shore, maybe not. Offshore at night, a transponder gives you an extra safety margin.
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Old 29-07-2017, 18:15   #15
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Re: How necessary is AIS?

I really don't understand how any experienced offshore skipper could downplay the importance of AIS.
Yes there are the commercial fishing boats without AIS but that pales in comparison to having a ship with a 100 ft beam coming up your stern on those dark rainy nights.
It is very reassuring when you can call them and they respond by saying "we see you and will be taking your stern".
My vote is for an AIS transponder even if money is an issue, put it on your CC and pay the frigging interest.
The anxiety relief will give you a longer life.
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