Jim - AIS provides a lot of value for very little investment, if your chartplotter already supports it. We can "see" the ferries before they come around the island or you can find out the SOG of that tug/tow to decide whether you can clear or need to tack away. It won't replace RADAR, but it augments your chartplotter a great deal in areas with significant commercial traffic.

I'd certainly miss mine if it failed for some reason.

Craig

[QUOTE=cillman;3124]Jim - AIS provides a lot of value for very little investment, if your chartplotter already supports it. We can "see" the ferries before they come around the island or you can find out the SOG of that tug/tow to decide whether you can clear or need to tack away. It won't replace RADAR, but it augments your chartplotter a great deal in areas with significant commercial traffic.

I'd certainly miss mine if it failed for some reason.

Craig[/QUOTE]

Agreed! We encountered some thick fog about 50 miles of the Atlantic Coast a few months back, and the AIS showed the names, direction/speed of travel, and any potential collision hazards for the 15 or so ships around us. For $400, the peace of mind was more than worth it.

I bought a receive only unit that integrated via MNEA 0813 to my Garmin 4208. It is both user friendly, and was reasonably easy to install. If you are considering one, I say go for it!

[QUOTE=akorinek;3145] the AIS showed the names, direction/speed of travel, and [B]any[/B] potential collision hazards for the 15 or so ships around us. For $400, the peace of mind was more than worth it.[/QUOTE]

I'm just learning about this and am considering one for my redesigned nav station (see other post), however, am I correct that you can only "see" the other vessels if they have a transponder? I know that commercial ships are required to have them, but it seems that a large non-commercial vessel would still be invisible on the screen. I guess I'm concerned that until it is required on ALL vessels, we may rely on it a bit too much and get whacked by a boat that doesn't have one. Also, since you have a receive-only unit, does that mean that you are invisible to others as well? Like I said, I'm still learing about it, so please correct me. I'm just concerned that the "peace of mind" it provides may be false and that we might rely on it too much and to our detriment. No doubt, though, that it's better than nothing.

Mike, your concerns about passive AIS are properly stated.

The title of Jim's original post was "AIS or Radar." And that question has not been answered yet, as all the comments have been AIS-related. Let's break this issue down...

Question #1...If you had only the wherewithal to invest in radar -OR- in passive (ie, receive only) AIS, where should you put your money?

There are things that ONLY radar can do for you. Properly operated, radar can see ALL the traffic that is out there, whether they are active-AIS-equipped or not. And radar can pilot you in severely restricted viz conditions, when GPS (perhaps due to failure?) is unable to. In almost every situation that I can imagine, a vessel would be better served with radar only, as opposed to AIS only.

But the fact is, radar and AIS are remarkably synergistic. Together, they will give you a level of situational awareness, and a collision avoidance package, that is unbeatable.

Question #2...OK, so hands-down you ought to get the radar first, but then, if you still wanted to invest in AIS, should you get a receive-only AIS, or the new AIS-B system?

The question is a little more difficult than that, as there are two choices of receive-only AIS, and also there's the AIS-B choice.

The two choices of receive-only are whether to get a single-channel AIS receiver, or a dual-channel AIS receiver. The single channel is the cheapest, but it is not nearly as effective in promptly receiving the transmitted signals of AIS-equipped vessels as is the dual-channel unit. So if you want a receive-only AIS system, go with the dual channel. The price difference between the two receivers is not much, and the extra amount buys you a significant improvement in monitoring. Also, that increment in cost will pale beside the larger investment that your decision will drive, whether you choose single- or dual-channel...that is, the biggest cost you will have is obtaining an AIS-capable display on which to see the AIS traffic superimposed on your nautical chart.

The dual AIS receiver typically runs 300 to 400 bucks or so, but your display choices can be much more costly. You will need a chartplotter that has AIS capability...and only in the last three years or so have these been manufactured with an AIS input. On the other hand you could use a laptop computer, but then you would need a GPS interfaced with it, and a nav software package (such as Coastal Explorer) to bring the entire picture together.

But receive-only AIS only will show the signals being transmitted by active-AIS-equipped vessels. Until recently, these were mostly the larger freighters, cruise ships, ferries, etc, where active AIS has been mandated for a number of years. Of course, these larger vessels are the ones guaranteed to kill you if you collide with them. But what about You? Your receive-only AIS can't transmit your vessel name, speed and heading, location, and other particulars...so nobody else will be able to see you on their AIS display.

AIS-B (a lower cost, lower power "transponder") was approved by the FCC earlier this year and is now being installed in good quantity. These "transponders" transmit as well as receive, so that other vessels' AIS-receivers will know where you are, what your vessel is doing, and will have your vessel name to be able to call you directly. AIS-B units are now running well under a thousand dollars. But remember, they still will have the same display requirements/investment as did the receive-only AISs.

I am seriously considering installing an AIS-B on High Flight, probably before the next boating season.

But the radar? There ain't no way I am going anywhere without that! Radar is non-negotiable.

[QUOTE=merrja;3158]I am looking to sell my 1999 36 mark II next year[/QUOTE]

:eek: Say it isn't so!

Thanks for the info Larry.

I should clarify that when I said any potential collision hazards I intended to mean any of the AIS vessels traveling on an intercept course. Naturally, it won't do anything for those vessels without a transceiver, nor am I visible with a receive only unit. So I certainly agree with Larry that the situational awareness provided is incomplete; but when compared to the situational awareness available without one, I feel much more comfortable.

I think two issues not mentioned in the radar/AIS debate are power and cost. I currently have 1 house battery, and 1 starting battery. If I were to instal a radar with that setup, it would mean installing another battery or two, and I think a conservative estimate for the overall cost, assuming I instal it myself would be somewhere in the 3-5k range (gross estimate).

When accounting for overall cost, and effort of installation I feel a stand alone AIS is a pretty useful tool in developing SA on the water. If cost is not a factor, and you are having it professionally installed a radar/AIS combo cannot be beat!