AIS & Internet Position Reports

A relatively recent addition to maritime electronics are Automatic Identification Systems (AIS.) These are ship mounted transponders that both broadcast the ships location, COG and SOG and report the same data from ships in the vicinity. Since they operate on the marine VHF bands their reach is about 25 nautical miles for big ships, 10 to 15 nautical miles for pleasure craft.* They are a real plus for sailboats as we are almost invisible on radar. Under the COLREGS sailboats have almost unlimited privilege. The powered vessels have to stay out of our way. In the old days ships frequently had to be in visual range to see a sailboat. This resulted in lots of close calls. Now they know we are here way out. It is fun to watch them tweek their heading a degree or two to give us a one nautical mile closest point of approach. One nautical mile seems to be the courtesy distance. They are a real safety boost.But, as usual, I digress. An unanticipated benefit of AIS is that it can be a passive