Wednesday, March 29

Why You Need AIS. A Primer

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Here’s a good primer about why you should have AIS on your boat, from America’s Boating Compass and the US Power Squadrons:

AIS, or Automatic Identification System, can make your boating safer. Consider the following scenario:

You have an AIS system on your boat. You are on watch, 20 miles off the coast, sailing in hazy conditions. An AIS alarm sounds on your chart plotter. Upon scanning the horizon, you see nothing.

When you return to your display, you see a target 5 miles ahead traveling at 23 knots and heading toward you. The AIS information data box shows that you are 10 minutes from Coastal Challenger, a 600-foot cargo vessel. Using the MMSI number supplied by your AIS, you make a Digital Selective Calling radio call to the vessel. The ship’s officer says he sees you on his AIS and radar. You both agree to turn 5 degrees to starboard. Within a few seconds, your chart plotter shows that the ship’s relative heading has changed, and you’re no longer on a collision course.

Now imagine that you don’t have AIS. When would you have spotted the ship? In haze, visibility is between 1 and 3 miles.

Suppose you see the vessel at 2 miles away and take 30 seconds to determine you’re on a collision course. You now have three and a half minutes to avoid the collision. If conditions are worse and you spot Coastal Challenger at a half-mile, that leaves you less than a minute to act. In fog, you might not see the ship at all. Hopefully, its radar will see you, but how strong is your boat’s radar signature? If you have an AIS transponder, the ship’s crew will see you, and you will see them.

With AIS, you can avoid collisions in crowded waters by knowing the names and locations of other vessels, how close they will approach, and when to act. Additionally, AIS broadcasts your boat’s information to other boats so their operators can make better, safer boating decisions.  Read more:







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