> Genuine question: All the commercial vessels continually broadcast their position, speed and bearing, right? Correct. AIS uses regular broadcasts, it’s not c

> Genuine question: All the commercial vessels continually broadcast their position, speed and bearing, right? Correct. AIS uses regular broadcasts, it’s not challenge-response. > Even if the military vessel does not do so, it should be able to receive all commercial vessels telemetry... Correct. Having an AIS receiver instead of an AIS transponder is a very typical setup for smaller sailboats or daysailors. If they’re not ready for the cost, complexity or power budget of a transponder, they can still pick up a receiver+plotter for $200, which will get them a little lcd with a map of traffic, CPA alarms, etc. Another $200 turns it into a transponder so that you show up on the other guy’s screen too. > So how can it possibly crash into one? The million-dollar question I guess. We manage to avoid it with a $400 radio and one pair of eyeballs on deck.