NavList:

Hi David

Reading that link I would say INS, as I suggested, is the primary navigation platform - initially and accurately aligned before being launched.

Most INS drift - and hence the modern ones are linked to GPS or such updating secondary links.

The information I have gleaned from the internet link suggests the AvTrak6 navigational technology is added to this Sabertooth platform to enable it to receive updates from oil field seabed transponders that have been pre-installed accurately for this sort of recovery type work.

3000 mteres down in the Wedell sea I can probably conclude there are no such transponders - and surface sonobuoys useless as they drift and generally passive listeners.

So in the case of this exploration I would suggest the inertial will be very accurate at launch and will degrade slightly as the time passes. However, a bit beyond my experience except I would suggest the bottom would have landmarks that could be used as fixes to provide relative positioning with the sonar.

But I doubt the vehicle would have enough power to do that itself except close in. Thinking out loud - have we any submariners on this forum.

Just an interesting aside - sound underwater can travel a long way - once top secret - the world oceans were laced with very accurately place listening sonbuoys set up to tract soviet subs - this informatio was declassified but I doubt anything exists in the Wedell sea - however - tracking submarines is an art and a science and the world oceans have complex layers which can cause sounds to be transmitted 1000s nms from its source.

And underwater navigation is a whole different kettle of fish.

My experience is all above sea level!!!

Regards Howard G

PS may be these guys can now go looksee for Amelia Earharts aircraft in similar depth water - all metal it should present a good sonar return and at 3000m be in relatively good shape!