Which INS alignment is used to get underway in less than 4 hours?

Master the Navigation, Seamanship, and Shiphandling (NSS) – Officer of the Deck (OOD) Phase 2 Exam with engaging flashcards and multiple choice questions, complete with hints and explanations. Prepare comprehensively for your test!

Getting underway quickly with an inertial navigation system relies on a mode that can be completed while the ship is moving. This is at-sea alignment. It uses the vessel’s own motion to establish the initial attitude and gyro references, so you can start navigation and rely on dead reckoning fairly soon—usually within a few hours and commonly under 4 hours.

Celestial alignment requires observations of stars or other celestial bodies to yield a highly accurate orientation, which takes more time. Rigorous static alignment needs the ship to be stationary and is aimed at the highest accuracy, taking longer than practical when you need to depart soon. Gyrocompass alignment pertains to aligning the gyro reference for the ship’s gyrocompass, but for getting the INS up and running quickly, at-sea alignment is the mode designed for underway use.