Reply to post: Depends on what you want to do.

Depends on what you want to do.

The answer is both yes and no. Depends what you are doing and how you are operating the AUV. If you are using something like a Hugen it uses INS and can't get a fix by it's self. So the data is accurate locally but not globally as in if you find two "things" you know very accurately where they are in relation to each other, but less accurately the the datum. If you are operating it directly then you can feed it positional updates via HiPAP (This is a very simplified answer) and you have a much more accurate system but you loose the capability to let it run by it's self. The biggest error in deep water is the Sound Velocity, an accurate SV profile is far more important that getting your GPS 5cm better. In deep water a carp SV can put you bathy out by tens of meters or more.