Naval Ships and Submarines Practice Test

Dead reckoning is estimating your current position by starting from a known fix and projecting forward using your heading (course), speed, and elapsed time. You take the last confirmed position, note how fast you’re actually moving and in what direction, and then advance that position on the chart for the time that has passed. If you know about drift from currents, winds, or tides, you account for those as corrections. The key idea is forward projection without relying on a fresh external position fix—you’re essentially “reckoning” where you should be based on how you’ve traveled. Because every small error in speed, time, or course accumulates, the estimate can drift the longer you go without an actual fix.

This isn’t about celestial sightings, which would determine position from stars, nor about GPS providing position updates from satellites, nor about estimating position from depth measurements. Dead reckoning focuses on a forward calculation from a known point using movement data.