It sounds like this system still needs a conventional communication channel between the receiver and a set of reference stations, right? So it'd be of limited u

It sounds like this system still needs a conventional communication channel between the receiver and a set of reference stations, right? So it'd be of limited use on a submerged submarine (though you could reconstruct your path post-facto after surfacing I guess ... actually, thinking about it, that alone is probably super useful for mapping and intelligence.)