Skip to main content

AIS for Sailors Page 2

Any sailor who has made extended passages along coastlines or across oceans has had at least a few close callswith big ships whose course and intentions can be difficult to discern until the last minute. The introduction of AIS (Automatic Identification System) has taken a lot of the guesswork (not to mention terror) out of these close-quarters situations. For just a

AIS-B vs. Radar

Radar is a boon for cruisers in all sorts of ways, but it’s not the perfect solution to dealing with shipping traffic. It’ll show you a target that you’ll be able to track, but it can’t see around corners or through land, bad weather and sea clutter can render it almost impotent, and using it well requires both practice and a degree of intuition on the user’s part. Shore-based AIS repeaters let you receive an AIS signal from a ship on the other side of a headland or an island. An ever-increasing number of navigation aids are also being equipped with AIS transmitters, which provides another level of security for cruising sailors. On the other hand, there are many boats and other hazards that aren’t equipped with AIS and that radar will (hopefully) be able to detect. If you have to make a choice between AIS and radar, these are the things to take into account. If your boat is already equipped with a late-model radar, you should be able to integrate the AIS into the system so that AIS targets are displayed on the radar screen. Talk about the best of both worlds…

Why a dedicated antenna?

You can buy an antenna splitter that allows your AIS to share your VHF radio’s antenna. Some of these splitters work better than others. AIS manufacturers almost all recommend, however, that you use a dedicated antenna that’s tuned to the AIS frequencies. A VHF radio antenna has to work across a wider range of frequencies. Since an AIS transmission is limited by law to 2 watts, it makes sense to use an antenna that’s made to transmit and receive on the two AIS frequencies. Such antennas are now widely available from specialist manufacturers like Shakespeare and V-Tronix—and some AIS makers also supply their own-brand antennas. Some even have integrated GPS antennas, further simplifying installation; these are often cheaper than an antenna splitter.

Going shopping

Class B AIS was only approved by the FCC for use in U.S. waters a few months ago, but it’s been operational in most of the rest of the world for years. There’s a wide range of equipment available to suit just about any budget; you can mix and match, or buy complementary equipment from just one maker. AIS data can be displayed on laptops, plotters, radar screens, or on dedicated AIS screens. Almost any plotter manufactured during the last two or three years should have AIS capability. Big names like Simrad, Raymarine, Icom, Furuno and ACR have all come out with AIS-B receivers and transceivers, and other companies like SevenStar, SR, Comar, SeaCas, Shine Micro, and SiTex are also making equipment.

Here’s a rough guide to choosing an AIS system:

Good: With an AIS receiver, you’ll be able to see other AIS-equipped vessels within the range of your VHF antenna—up to 40 miles or so, depending on antenna height, though some users report seeing targets as far away as 70 miles. If you already use a laptop with electronic charts, you can set up a receive-only AIS system for relatively little cost. You'll need a receiver, a GPS antenna, an antenna splitter that lets you use your existing VHF antenna, and the cables to connect it all together. This will display data from vessels equipped with AIS A and B on your laptop—if, that is, your charting software is AIS-compatible. You can buy a single channel receiver for less than $200; dual-channel receivers go for two to three times that.


Better:
Laptops are great, but since they’re not waterproof you’ll have to go below to look at the screen, and this isn’t good if you’re the only one on deck. Better to be able to see ships displayed on a plotter in the cockpit so you can stay at the helm, ready to act. And it’s also better to let the ships know where you are. Even better is to have the ability to overlay AIS targets on a radar screen. You’ll want a Class B transceiver, dedicated GPS and AIS antennas, and the relevant cables. Most transceivers will come with all of this gear. Check that your plotter is AIS-compatible. Dual-channel receivers vary in complexity and features, which accounts for the wide disparity in prices, from under $500 up to around $1,000.


Best:
I think the best set-up for a short-handed cruising boat is this: a transceiver, all the other gear, and a dedicated cockpit AIS display like the Simrad A150 or AISWatchMate. Priced from around $500 to over $1,000, these units let you keep a close eye on the movements of approaching vessels, while leaving your plotter or laptop free for other duties. They'll make it easier to calculate the chances of a collision, which is what AIS is all about.

To B or not to B

Who needs AIS? If your cruising grounds are bisected by busy shipping lanes, or if they are prone to fog, you should certainly think about it. If you’re planning to do some overnighters or offshore racing, AIS would be a worthwhile investment. If you sail in areas where there’s little or no commercial shipping activity, don’t bother.

The dangers of AIS

Like any electronic gizmo, AIS can foster a sense of dependence. It’ll let you know about Class A-equipped commercial ships and Class B-equipped sailboats and powerboats; but there are plenty of boats out there that don’t have AIS. The Coast Guard also warns that some commercial ships have outdated AIS software that won’t pick up Class B transmissions, so you can’t be sure every ship will see you. If you treat AIS as an aid to safe sailing that backs up your own senses, rather than an oracle to be obeyed to the exclusion of all else, you should have no problems.

Resources

ACR

Comar, Smart Radio, AISWatchMate

Icom

Raymarine

SeaCAS

SevenStar

Shine Micro

Simrad

Si-Tex

Related

00-LEAD-210918_11HR_AZIMUT48HRS_AMO_00411

11th Hour Racing Team's Green Mission

“I’ll admit, it’s still hard to watch the boat leave the dock sometimes,” says former Volvo Ocean Race sailor Mark Towill. Since meeting during a Transpac campaign over 15 years ago, he and his teammate Charlie Enright have sailed thousands of miles together aboard two Volvo ...read more

D61_JKELAGOPIAN-3

Boat Review: Dufour 61

Dufour, long one of France’s most well-respected builders, has been producing sailboats in La Rochelle since the dawn of fiberglass boatbuilding. Having recently merged with another La Rochelle-based builder, Fountaine Pajot, Dufour has now joined other European mass-production ...read more

m138123_14_00_210609_TORE02_SE_2152_2504-2048x

The Ocean Race to be “Climate Positive”

The 2023 Ocean Race intends to be one of the world’s first climate positive sporting events, offsetting more greenhouse gasses than are produced. The two-fold effort means cutting emissions by 75 percent and investing in ocean projects that sequester carbon and restore ocean ...read more

01-LEAD-Ancients-3-2048x

Cruising Lake Superior

Almost anywhere a sailor drops the hook someone else has been there before. We are hardly ever the first. That remote Maine harbor without a soul in sight: there’s a lobster trap. The south coast of Newfoundland: the crumbling remains of a fisherman’s cabin lie hidden among the ...read more

01-LEAD-Tablet-Holder-4

Fabricating a Tablet Holder

During the pandemic, I was stuck aboard Guiding Light, a Lagoon 410, in St. Lucia for over a month. During that time, as I worked on the boat, I started by doing a spring cleaning in my spares locker and finding some parts and material that I forgot I had. As soon as I saw them, ...read more

00-LEAD-AdobeStock_486335954

A Catamaran for a New Era

Anacortes, Washington, is an unassuming sea-salty town near the San Juan Islands of Puget Sound, and the Betts Boats yard is easy for a passerby to miss. But within Betts’ facilities, the dawn of an era in Pacific Northwest production boatbuilding could be breaking with the ...read more

X5_plus_slide-01

Boat Review: Xquisite X5 Plus

The Xquisite X5 Plus is a major update of the boat that SAIL awarded Best Large Multihull and Best Systems titles in 2017. The changes were not just cosmetic, but genuine improvements to an already fine boat, making it lighter, faster and less dependent on fuel. The builder’s ...read more

01-LEAD-AdobeStock_40632434

Cruising: Offshore Prep Talk

When I began preparing Minx, my 1987 Pearson 39-2, for extended Caribbean cruising, I had to balance my champagne wish list against my beer budget. Every buck spent on the boat before leaving would be one less frosty can of Carib down in the islands. On the other hand, I had to ...read more