AIS (automatic identification system) uses special VHF frequencies to broadcast the position of AIS transceiver-equipped boats on a chart plotter. While designed to be a navigational safety tool, the AIS system can also be employed to quietly communicate your position to an AIS-equipped buddy boat. Here's an example of how it might work: Let's say the two of you are trolling offshore water, looking to catch some yellowfin tuna, and you find the fish. To call your buddy in on the bonanza, you send a coded VHF voice message, like "The eagle has landed," on a predetermined channel. That's your buddy's cue to look for your boat's AIS symbol on the plotter.