Navigation, Seamanship, and Shiphandling (NSS) – Officer of the Deck (OOD) Phase 2 Practice Exam

EP also applies to DR position when which condition exists?

When GPS is available

When a running fix is used

When there is questionable accuracy about the ship's position or set and drift applied

When you’re navigating by dead reckoning, your position is projected from a known fix using speed and course, but errors accumulate over time—especially from unknown currents (set and drift) and chart/motion inaccuracies. EP, or estimated position, is used to re-estimate your actual position when you don’t trust the DR result. If the ship’s position accuracy is questionable or the set and drift that have been applied to the DR are uncertain, applying EP allows you to correct the plot with independent information (a fresh fix, radar, celestial, etc.) and keep the position estimate credible. This is the moment to bring in an updated estimate rather than continuing with an unverified DR.

Only during a voyage's end