January 21, 2010

Small-boat AIS

EVERY NOW AND THEN I try to contact an ocean-going ship that seems determined to run me down. But I always have to think long and hard about how to do it. The trouble is that I don’t know the name of the ship, so I switch on the VHF to Channel 13, which he is supposed to be monitoring, and I say: “Ocean-going vessel proceeding south past Migley Point, this is the sailboat Sangoma dead ahead of you. What are your intentions, please?” Or something like that — long, wordy, boring, and ineffective. It rarely brings results, probably because they know only too well that if it comes to the worst, I’ll switch on my engine and scoot out of their way.

Now I see there is an answer to my problem. They’re making a yacht-sized, receive-only version of the Automatic Identification System (AIS) that big ships must carry. I first saw AIS in action about three years ago, when I was traveling by Royal Mail Ship to the island of St. Helena. Out there in the middle of the lonely South Atlantic, I was on the bridge when a ship appeared on the horizon. I glanced at the officer of the watch. He turned to the AIS. “We’ll miss her,” he said reassuringly, “plenty of room.” Then he told me her name, her call sign, her speed, her heading, and even her cargo. All that, and a lot more, was on the AIS screen. At the same time, our ship was automatically broadcasting its own information for the other ship to pick up. There are no longer any secrets on the ocean deep. Here are just some of the pieces of information AIS provides:

IMO ship identification number - a seven digit number that remains unchanged upon transfer of the ship's registration to another country;
Radio call sign - international radio call sign, up to seven characters, assigned to the vessel by its country of registry;
Name - 20 characters to represent the name of the vessel;
Type of ship/cargo;
Dimensions of ship - to nearest meter;
Location of positioning system's (eg. GPS) antenna onboard the vessel;
Type of positioning system - such as GPS, DGPS or LORAN-C
Draft of ship - 0.1 meter to 25.5 meters;
Destination - maximum 20 characters; and
ETA (estimated time of arrival) at destination - UTC month/date hour:minute

You can get two versions in yacht sizes now, a receive-only set for about $500 and a send-and-receive set for about double that. It’s still expensive, and left to myself I don’t think I’d be getting an AIS set for my 27-footer any time soon but I have a nervous First Mate and I know she’d just love it if I could switch on Channel 13 and make definite voice contact by saying: “Ocean Monster, Ocean Monster, for gawd’s sake look where you’re going! That little speck in front of you is me.”

Todays’ Thought
Out of the abundance of the heart the mouth speaketh.
— New Testament, Matthew xii, 34

Boaters’ Rules of Thumb #5
Anchor scope: Under favorable weather conditions, minimum scope should be five times the depth of the water, measuring “depth” from the anchor roller down to the sea bed. In strong winds and/or currents, a scope ratio of 7:1 is preferable, or even 10:1 if you can find the swinging room. (“Scope” consists of the total anchor line, including both chain and nylon line.)

“Is my face dirty or is it my imagination?”
”Your face is clean. I don’t know about your imagination.”

1 comment:

Jennifer Moran said...

Hello John, As an interim measure (and a much cheaper one), if you have an iPhone, you can download the receive version of AIS from the App Store for a very small amount of money. Alternatively, if you have a laptop with wireless broadband or some other way of accessing the internet on your boat, you can go to http://www.marinetraffic.com/ais/
It's fantastic!
Best wishes, Jennifer