You are sort of confusing it with a Convergence Zone I think. Those occur every 30 miles while the Deep Sound Channel sucks in certain frequency tonals in for lack of a better word vortex a couple of hundred feet tall where sound waves refract back and forth very quickly across the axes of the channel.

Take a look at this:
http://img255.imageshack.us/img255/2662/raystest.gif
at about -1 (thousand meters) is the DSC. The larger bounces are the convergence zones. if your sensor is above or below the axis then you could lose the contact as the sound waves bounce (you would be in their "Shadow Zone") but if its in the axis then the waves are bouncing along such a narrow corridor that you can't miss them.

I'll take your word for it. I know just enough about sonar to sound impressive, but do no more than just confuse myself and others.

That's been possible for quite a few years according to a friend of mine who was a PO in sonar.

I'm not entirely convinced about the accuracy of tracking at such ranges though...not that any navy is going to go public on precise details.

The novice sitting at my end of the wire assumes that this is the detail to be aware of. I would not believe this capability to be the normal state of things in submarine operations, but being the result of several factors meeting in time and space.

Well I'll put it this way, in certain regions of the world like the North Atlantic or the Pacific where the waters are very deep its possible if you have a sensor also in the deep waters and the acoustic conditions are uniform. But there are many things that can mess it up like a current of warm water.

Lets take the locations of the SOSUS stations as a base.
http://img96.imageshack.us/img96/845...usesensors.png
Lets assume we would not design a system with any gaps, now draw a circle around each station (assuming the arrays are within a 50 or miles of the station on the edge of the continental shelf). Now lets remember back to the Cuban Missile Crisis where the Soviet Foxtrots were basically detected every time they snorkeled by SOSUS and it gave the Ship and ASW Plane commanders an area sufficiently small to search. That was 50 years ago, in the 1980s we started putting this on surface ships (SURTASS), its very possible today that systems of this scope are small enough to install on a submarine.

That's just the tracking methods we know about.

I know the Russians put a lot into wake detection on their boats, and there was talk of using lasers to probe the depths either from a submerged boat, surface ship or satellite in orbit. However, given the loss of energy water would cause a laser, I'm not sure if that's particularly practical. :hmmm:

Yea lasers stop being effective after about a 100 feet. Although Helis do use them for mine detection.

The wake detection sensors the Russians developed were mostly abandoned, the latter model Akulas either had them removed or they were never installed.