The vast majority of the time, boats don’t use active sonar. Whilst giving a high resolution view of what’s around them, it also allows any other signals collector (often defined as an enemy aggressor) to accurately pinpoint the location and deploy countermeasures, even if only updating threat assessments.
Ultra detailed charts are used that have the terrain mapped. Occasional positional fixes when a boat surfaces can be used to ‘reset’ where they thought they were whilst running silent.
"Occasional positional fixes when a boat surfaces can be used to ‘reset’ where they thought they were whilst running silent."
Yeah, fair enough that makes sense, but what I've read about modern underwater inertial navigation systems is their remarkable accuracy. You'd think that any selected course for the sub would be set well within the tolerance of the inertial navigation system thus the sub would steer well clear of any known seamount. Alternatively, it was uncharted and that brings me back to the accuracy of the maps.
P.S.: I'd also read somewhere that as part of the underwater navigation system that gravity detection was also used and it is sensitive enough to detect changes caused by massive nearby objects, seamounts etc. As they're passive detectors that wouldn't preclude them from being used all the time.
