Coastal Navigation Practice Exam 2026 - Free Coastal Navigation Practice Questions and Study Guide

In dead reckoning you estimate your position by advancing from a known fix using the vessel’s course, speed, and elapsed time. You start from a known point, set a course to steer, and estimate how fast you’re moving. The distance you cover is speed multiplied by time, and you plot that distance along the chosen course from the fix to arrive at your estimated position. That combination—how long you’ve traveled (time), the direction you’ve sailed (course), and how fast you’ve moved (speed)—is exactly what lets you calculate where you are without new observations.

If you only have time, you don’t know how far or in which direction you’ve moved, so you can’t determine a new position. Celestial observations would provide a precise fix, not a dead reckoning estimate. Depth measurements don’t give your horizontal location. For a quick example: steering 60 degrees at 12 knots for 0.5 hours covers 6 nautical miles along 60 degrees from the last known position, yielding your estimated new position.