Isn't this the method used by the sub in Hunt for Red October? Or did they also use a gyroscopic and look for changes in the gravitational vector, not just its magnitude?
I haven't read the book, but in the film the problem was the Red October was using the caterpillar-drive https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive (and not a propeller/impeller) but a chance detection by Dallas' sonar along with the ingenuity of Dallas' sonar operator, who figured out how to detect and track Sean Connery's boat. Nothing to do with gravity or gyroscopes at all.
Yes, but Red October had some super accurate underwater gravity map of some kind that allowed them to navigate at speed through areas Dallas couldn't follow IIRC.
Red October used the usual gyroscopes approach that gets more and more inaccurate as it sails. I think a key plot point is that they need to surface to take a latitude / longitude , precipitating much suspense.
