Do I need AIS?

[Kache Walk]

Sorry for the confusion my original post may have caused. Just goes to show how little I knew and why I needed to ask the question! I searched through the archives and watched a few YouTube videos and your answers are helping a lot. Since I can connect the VHF to the chart plotter, the decision boils down to whether the VHF with AIS receiver is $100 better than the VHF with no AIS but GPS built in. Seems like the latter is redundant to the GPS I already have. And while I can't send, I can see what's coming at me, id the boat, and call them if I need to.

[Tomm0]

Vhf with DSC and a built in GPS saves you attaching one, but I assume the other model, with the ais receiver, also has nmea-in for location polling and distress purposes ?

[GrowleyMonster]

Get a transciever. Let the other guy see you.

But first get your FCC Ship Station License. That way you get an MMSI from the FCC and your radio equipment is legal pretty much anywhere in the world. If you will never sail foreign, then you could get by with a 3rd party issued MMSI, I think, but I recommend going the whole enchilada and getting the FCC license and MMSI.

[jeremiason]

You buy what you can afford...

Having an AIS receiver is better than not having anything....

Under todays Federal and IMO rules, Commericial Vessels over 300 tons no longer have to monitor Channel 16 since they have Digital Selective Calling or in the Commercial world "GMDSS".

As a result of this rule, and if the ship isn't monitoring Channel 16, the only way to contact them is to find their MMSI number on the AIS display and hail them usnig your DSC.

[Dockhead]

I'm surprised no one has asked where and how you sail. If you are doing coastal sailing away from shipping lanes, with little fog and little night sailing, and you're never worried about ships running you down, then you might really not need any kind of AIS.

If you sail in or near shipping lanes and/or at night or with much risk of fog, then AIS is worth its weight in gold. Then you'll want a full transceiver which sends your data out as well as receiving it from other vessels. These are now so cheap that there is hardly any reason not to go the whole hog, if you need AIS at all.

[conachair]

Originally Posted by Bash

The way you asked the question is a bit ambiguous. Whether you will need AIS is a different question than whether the VHF you propose to buy will provide what you need.

With the VHF unit, you'll be able to see me but I won't be able to see you.

Is that good enough?

Let's put it another way: With the VHF unity, you'll be able to see ships but they won't be able to see you.

Good enough now?

From experience offshore on a steel boat they could always see me on radar so receive is fine , plenty good enough in that example. Receive is great, offshore watching the big stuff make course change to give you more room while still over the horizon is comforting. Making sure you have a good radar echo could arguably be more beneficial than transmitting AIS.

[hpeer]

He's doing coastal cruising, East coast and Chesepeak.

Buy a transceiver. If you have a Rx you can see him. If you tx he can see you. There are a lot more of them than you so it is better than twice as good. Also, their lawyers know your widow has a better chance of winning a suit if you were txing.

[MarkJ]

See the screen shot below and you will see a ship divert from hitting me because they see me on AIS.

Now, look more carfully at the screen shot... Not ONE ship has diverted but THREE ships!

I didnt call any of them.

6 knots cant avoid 20 knots like 20 knots can avoid 6!

[Kettlewell]

Sure, AIS would be nice to have, but you don't "need" it. If you're getting a new VHF anyway I would consider the one with the built-in AIS as an easy way of getting it.

[conachair]

Originally Posted by MarkJ

See the screen shot below and you will see a ship divert from hitting me because they see me on AIS.

Now, look more carfully at the screen shot... Not ONE ship has diverted but THREE ships!

I didnt call any of them.

6 knots cant avoid 20 knots like 20 knots can avoid 6!

Are you sure it was ais they were looking at and not radar or visual? Not that I'm anti ais transmit in any way, doubt if I'll ever get a transmitter for cost reasons, both financial and power. Plus they all see me on radar anyway.

Instinctively I would put having a good radar echo a bit higher than ais transmit (or ideally both ) , but really have no idea how the big boys work, do they watch the radar more or does it all end up on the same screen? Any big boat drivers around here?

[goboatingnow]

since they have Digital Selective Calling or in the Commercial world "GMDSS".

GMDSS is predicated in GMDSS, its merely part of it. GMDSS is a the organisation of distress alerting and response and the organisation of rescue assets.

Are you sure it was ais they were looking at and not radar or visual? Not that I'm anti ais transmit in any way, doubt if I'll ever get a transmitter for cost reasons, both financial and power. Plus they all see me on radar anyway.

Instinctively I would put having a good radar echo a bit higher than ais transmit (or ideally both ) , but really have no idea how the big boys work, do they watch the radar more or does it all end up on the same screen? Any big boat drivers around here?

AIS transponders are much more useful then a receiver. Firstly , a bit like elephants and mice, large ships , if they know you are a small sailboat , like to keep far away. And MarksJ experience echoes mine, they will change course , often over the visible horizon to avoid you. Without positive ID they tend to sail into visible contact.

While owners of steel vessels might feel comfortable, I can say categorically that a average GRP boat in a seaway is practically invisible to ships radar. I regularly make it a point to talk to passing ships and id say 8 of 10 did not have a radar fix on me , until I gave them a rough direction in which to search.

It at all possible financially , forget receive only, in a couple of years they will all be gone anyway, you can get transponders for not much more money and they provide a better experience.

I would go as far as to say , if you sail in busy waters, an AIS transponder such be up there with your depth gauge.

Note it isnt radar and isnt a substitute for one. If you can afford radar get one.

To answer your question , having been on the bridghe of several large ships, They are driven by radar, AIS is overlaid on the modern ECDIS/glass bridge systems but in many ships its still a Class A AIS with a little text display and keyboard.

DAve

[GrowleyMonster]

Typically AIS targets show up on the ECDIS. Radar targets that are plotted on the ARPA are also displayed on the ECDIS. A sailboat might be visible on radar from 4-5 miles away, or maybe only from inside a mile, depending on the boat, sea state, and whether there is a radar reflector or not. Visual sighting depends on of course visibility, but remember from a ship's bridge we are looking at a lot more ocean than you are looking at when your height of eye is only 7 or 8 feet. I have spotted large sailboats from 10 miles in daylight with good visibility, and at night when the sailboat has exceptionally bright lights.

So far I have ran across only a few sailboats with AIS transponders. But AIS targets, even class B, typically show up at 20 miles or more. They are listed on the AIS screen usually in order of range, and if there are several screens worth, maybe a distant AIS target won't be noticed until it is in the first page, which might put it within 6 or 8 miles when there is considerable traffic.

Just because you see me on my ship does not mean I see you. I am a lot easier to see, on a 900 foot ship, than you are on a 30 foot boat. We do the best we can, but you would do well to make it easier for us.

Anyway, we see you on Radar, Visually, and on AIS. The range at which we notice you varies with conditions. The more ways we have of noticing you, the better. So it is not a question of which one works the best. All three have value, and any 2 of them is better than one. All three is better than 2.

A basic AIS "black box" type transponder is well under $600. That's half the cost of the cheapest radar you can get, and it not only alerts you to a ship's presence, but it is one more way of alerting the ship to yours. Current drain is modest. Really, there is no reason not to spring for a full AIS transponder. It could save your life some day. No, it is not perfect, but it helps. Look at it this way... you can not possibly be worse off for having AIS, right?

But don't be satisfied with navigation lights that barely meet the minimum requirements, and don't sail without a radar reflector. A bold colorful design on your sails is a big help. Look at all the ways you can make yourself noticed, not just one.

[David M]

Originally Posted by MarkJ

6 knots cant avoid 20 knots like 20 knots can avoid 6!

Mark beat me to the most important reason for having a transceiver.

Good luck trying to maneuver a safe enough CPA with something that goes 5 knots away from something that goes 20+ knots. It's much safer if the faster vessel sees the slower vessel because the slower vessel has a transceiver.

[conachair]

Originally Posted by goboatingnow

AIS transponders are much more useful then a receiver. Firstly , a bit like elephants and mice, large ships , if they know you are a small sailboat , like to keep far away. And MarksJ experience echoes mine, they will change course , often over the visible horizon to avoid you. Without positive ID they tend to sail into visible contact.

That's actually why I'm not too bothered about transmit, offshore they do just that, alter course quite often when still over the horizon, it just hasn't been a problem. If they have waited for positive ID I haven't noticed it as the course changes have always been so far off. Any I've spoken to have had me on radar for about 15 miles from memory.

But would still like one, just not as high up the list as other bits. As for receive, it's hard to see why anyone wouldn't have one on board, you can spend more on a wet weather jacket.

[goboatingnow]

That's actually why I'm not too bothered about transmit, offshore they do just that, alter course quite often when still over the horizon, it just hasn't been a problem. If they have waited for positive ID I haven't noticed it as the course changes have always been so far off. Any I've spoken to have had me on radar for about 15 miles from memory.

Thats teh idea, but in a GRP boat , unless you tell them you're there they wont see you.

Dave