Re:Maybe today’s Navy is just not very good at driving ships
by soneil on Monday August 28, 2017 @03:23PM
(#15119299)
> 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.
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.