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jgsteven 02-09-2009 12:49 PM

Opinion wanted: Is RADAR mandatory for Cruising, or just get AIS?

I am looking to do a bit more extended cruising, and am concerned about collision avoidance. I am considering two solutions:

1. Radar unit installed on the mast
- Very expensive, have to unstep mast, etc
- I don't want to put a stern mounted pole on my boat
- May not be able to fix it myself if it breaks


2. Adding an AIS class B send/receive to a chartplotter
- Much cheaper, can install myself, can buy those new sails sooner, etc

I realize radar is the 'gold standard' for collision avoidance, but is it still necessary? It is my understanding that cargo ships must transmit AIS info, and so it should be as good or better at finding the big boys, while smaller ships without AIS may not show up on radar either.

My feeling is that AIS along with the standard 15 minute visual check should be a comfortable level of safety while cruising -- and that even with RADAR it wouldn't be safe to skip the visual check. is option 2 enough? Or should I bite the bullet and shell out for option 1?

Your opinions are appreciated.



RanAweigh 02-09-2009 01:17 PM

While AIS is a nice tool you are presuming that ALL vessels in your transit are is participating. This is probably not the case. AIS depends on the participation of others to provide information to you.

Radar is an active instrument giving you a real time image of objects around you. While there are situations wherein objects may be masked on radar it is fewer occasions than a vessel not having AIS. A properly tuned, quality radar system will display some pretty small objects. I routinely see fishing floats at greater than a mile out.

You don't really need a "pole" if you don't want it. There are mounts that fix to the backstay.

If it came to a choice of a chart plotter or radar I'd choose radar. Inshore you can navigate by radar a chart plotter won't tell you that you are about to be run down by that cigarette boat.

AjariBonten 02-09-2009 01:42 PM

When all the buoys, islands, drunken stinkpotters, etv have AIS, then maybe.

I can say that in an unfamiliar area, RADAR is an absolute essential navigational AID, just like GPS, charts, binoculars, and a rested and sober mind.

Omatako 02-09-2009 02:47 PM

When there is a fog down and you are sailing between a few dozen islands/rocks, AIS is as good as tits on a rain barrel.

Go for radar.

sck5 02-09-2009 03:08 PM

I am putting radar on my boat after being out on the Chesapeake last fall when suddenly a pea soup fog came down as I was approaching the Bay Bridge. Couldnt see ANYTHING. Sure, the chartplotter told me where it thought I was but a radar can not only show you those landmarks for REAL but also where the other boats/ships are. Freighters move fast enough that if you wait until you can see them in a fog you may well already be toast.

Paul_L 02-09-2009 04:28 PM

Comparing Radar to AIS is not really very valid. You did not describe the type and location of sailing you plan on. If you are sailing in areas that have limited fog, then Radar is much less of a must. Boats have been cruising for a long time without Radar. It is only in the last 10-15 years or so where small Radar prices have come down so much that many more boats have Radar. On an overnight passage it is nice to be able to turn on the Radar and see whats out there and what way they are going. Get caught in fog a few times and you'll see the value very quickly.
AIS prices have come down so much that it is a nice safety feature, independent of Radar. Most can be left on continuously with a much lower current draw than Radar.

Paul L

jgsteven 02-09-2009 04:56 PM


Originally Posted by Paul_L (Post 445702)
Comparing Radar to AIS is not really very valid. You did not describe the type and location of sailing you plan on.

Fair point, sorry.

I sail San Francisco bay and the surrounding coastal areas. I am a desk jockey during the work week, so I only occasionally cruise. I am looking at making some longer trips this year, to places such as Catalina Island (~450nm) when I can get some vacation and am thinking about changes I need to make to the boat.

It looks like I can get an AIS send/receive along with a little plotter display from for about $1300, and be able to install it myself. RADAR is more like $3000+ for an entry unit, and uses significantly more power as was pointed out. (right now the boat uses almost no energy, and it would be nice to keep it that way)

So, RADAR users out there: Do you leave it on all the time? Or just for the occasional check?



btrayfors 02-09-2009 05:31 PM

Used to teach sailing on SF Bay (Cass Sailing Marina, Sausalito). I remember all those times sailing in thick fog and nasty rainy conditions. Radar would be a very valuable addition.

For coastal cruising as well, radar is a wonderful tool. In fact, experienced navigators would likely rate it as the 3rd or 4th most important navigational tool aboard, after the compass and fathometer!

You can't really compare AIS to radar. AIS is a passive device which displays information about boats which transmit an AIS signal. Not all boats. In fact, only some large commercial vessels. Not fishing boats. Not yachts. Not runabouts. Not sailboats. Not buoys. Not islands or coasts or rocks. Not storm systems.

Guess as an older navigator I'm not much enchanted with AIS. For many, I think it could be a distraction, luring them into a sense of comfort by displaying information on a screen about SOME large vessels, while distracting them from using the most important navigational tool of all: the Mark I eyeball :-)


Paul_L 02-09-2009 05:57 PM

Sounds like you are looking at an AIS receive/transmit system. When I said cheap, I was referring to the receive only units.

You can get into a low-end Radar only for a lot less than $3k these days. Make it a radar chart plotter, 4kw, etc then the price goes way up. A Furuno 2kw unit with a 6in B&W LCD display is around $1,350. The radar install is more time consuming. Given where you sail and your plans, radar would be nice.

Paul L

Faster 02-09-2009 05:57 PM

We've just returned from a week's sailing in Mexico on a boat with a chartplotter, latest available "charts" and radar. The official charts of the Mexican coast are appallingly bad.... every where we anchored the plotter showed us to be up to a 1/2 nm "inland".

Making a landfall (or simply negotiating a group of islets or a headland) in the dark in this region without radar would be scary as hell. Radar is so much more than a tool for collision avoidance with another vessel.

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