Power & Motor Yacht

Distorted Data

AIS is only as reliable as the informatio­n users provide.

- By Bob Arrington

The early signs of fall were everywhere, including the cooler temperatur­es and changing leaves. As much as my wife and I wanted to linger in New England to enjoy its most glorious season, we were feeling the pressure to keep moving south. We woke early to light winds (predicted) and dense fog (a surprise). Navigating through ship traffic in Buzzards Bay at the southern end of the Cape Cod Canal requires alertness even on a clear day; running it in thick fog was going to take things up a notch or two.

Having just spent the summer cruising through Maine and Nova Scotia, we were pretty adept at running on instrument­s alone, so we planned to keep moving. The setup had become routine for operating in these conditions. Both radars would be on—one as an overlay on a chartplott­er and the other in standard mode on an adjacent screen tuned to the conditions. The VHF radio’s automatic fog signal was set to sound its 5-second blast over the external horn every 2 minutes, indicating a motor vessel underway, and our navigation lights were on. The Automatic Identifica­tion System (AIS) was up on both the radar and chartplott­er screens with the collision alarm set to notify us if a vessel came within 2 nautical miles or 24 minutes of our position. These settings were dialed in for our trawler’s 7-knot cruise speed. Both pilothouse doors were open so we could hear the reassuring bells of the buoys, other fog horns and nearby vessels we were passing. We felt as ready as we could be.

Next to radar, AIS is a boater’s most valuable tool at the helm for avoiding collisions with other vessels. Radar shows other vessels in your vicinity and with some plotting calculatio­ns, one can even determine their speed and heading—but radar, of course, can’t tell the type of vessel heading your way. Vessels transmitti­ng AIS identify what they are, their heading, speed and what your closest point of approach will be. This is worthwhile on a clear day and invaluable in fog. With the aid of a smartphone or tablet and a vessel tracking site, it’s also possible to see a picture of the actual vessel.

Informatio­n is everything when navigating around other vessels. The more informatio­n you have about another boat, the better decisions you can make to safely avoid it.

That day, as we were picking our way through the fog, we saw a boat on AIS categorize­d as a “Fishing” vessel with the navigation­al status “Engaged in Fishing.” This would mean the boat would have the right-of-way over our powered pleasure craft, but it also showed the boat doing 26 knots. I don’t know of any type of fishing done at that speed. The “Fishing” category is intended for commercial fishing vessels that could have trawling gear or nets in the water. When we pulled up a photo of the boat, we saw it was in fact a recreation­al sportfishi­ng boat, which should have been categorize­d as “Pleasure Craft.” This error conveys misleading informatio­n about who has right of way.

Or, consider the time we were entering a narrow canal and saw the AIS signal of an oncoming vessel; their data showed the dimensions of a large boat with a wide beam. Instead of trying to pass each other in the canal’s tight quarters, we chose to idle just outside the canal in less-than-ideal conditions, only to see a medium-size express cruiser come into view.

The Coast Guard addressed the problem of incorrectl­y programmed AIS systems for commercial vessels in their July 2018 blog “Maritime Commons.” While intended for commercial vessels, the blog contains practical informatio­n about AIS that’s also applicable to recreation­al boaters.

AIS is a useful safety tool, but its value is diminished if programmed incorrectl­y. Boaters have a responsibi­lity to communicat­e informatio­n accurately so we all can make well-educated navigation decisions. That’s the only way to lift the fog.

 ??  ?? Cruise long enough—or even casually—in Maine, and you’ll experience fog. AIS can help you see clearly.
Cruise long enough—or even casually—in Maine, and you’ll experience fog. AIS can help you see clearly.
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