I mentioned the Automatic Identification System (AIS) in the previous post. The system was originally devised for collision avoidance by continuously transmitting vessel information on VHF Radio frequencies. This information includes the vessel's identification, position, speed, and course, along with other relevant information. Other vessel's and land-based stations can monitor this information. AIS worked so well, its use was made mandatory world-wide in 2002 for all passenger ferries and by all ships exceeding 300 gross tons.

Standing in the cockpit of Distant Horizon, the visible horizon is about 3.5 miles away. When a ship is spotted, it will take about 20 minutes for that ship to overtake Distant Horizon. That leaves a few precious moments to ensure we are not on a collision course and, if we are... then, to take evasive actions.

VHF radio waves travel in a straight line from antenna to antenna. My VHF antenna is at the top of the mast; just over 50 feet above the water. Typically with VHF the range would be 25-30 miles or so. Using AIS, gives a ships direction and speed at nearly eight times the distance as compared to visual means. This extends the safety zone around Distant Horizon. Additionally, in heavy rain, fog, or haze, the AIS can still "see" ships at a safe distance.

Standard Horizon GX2150 AIS Matrix+

Rather than installing a seperate AIS receiver, I chose to purchase an integrated system using the Standard Horizon Matrix AIS+ VHF radio. With the remote mic in the cockpit, all the AIS information is right there. AIS doesn't replace keeping a good watch. It provides additional information to those on watch; making each voyage safer.

Another use of AIS, which I have found extremely useful is obtaining a current weather forecast.  Since I know the ship's name, I can hale them on the radio. When requesting the latest weather forecast from a ship, they will respond with their current three day forecast; allowing us to have a current weather forecast available at most times.

I have heard people say that ships won't answer such a radio call. In my experience, that has happened exactly once... and that ship had no markings. So, I assumed it was a military ship.Even before AIS, I have never failed to communicate with a commercial shipping vessel at sea. It's not luck. The international language for commercial communications is English. This is true for maritime shipping as well as aviation. Most ships have crews from countries where English is a second, possibly third, language. They are required to log their radio communications. So, given the opportunity to speak English, the person on watch always does respond.