Calculating current position using a known past position, then advancing it using speed, course, and elapsed time.
Quick facts
Regulation
SOLAS Chapter V
In practice
Despite the ubiquity of GPS, dead reckoning remains a critical skill and a mandatory STCW competency. SOLAS Chapter V requires that watchkeepers maintain continuous awareness of the vessel's position; when GPS is unreliable—in high-latitude polar waters, near GPS jammers, or during spoofing incidents—the DR plot on the chart or ECDIS provides the only means of safe navigation. IMO Resolution A.953(23) on the world-wide radionavigation system emphasises that no single electronic navaid should be relied upon exclusively, reinforcing dead reckoning as an indispensable discipline for every officer of the watch.
Regulatory detail & full definition
Dead reckoning (DR) is the method of estimating the current position of a vessel by projecting forward from a known previous fix using the ship's speed through the water, the course steered, and the elapsed time. Bowditch (American Practical Navigator) treats it as the fundamental fallback technique when electronic position aids are unavailable or uncertain. The DR position does not account for leeway, tidal streams, or current; when these are estimated and applied, the result is called an estimated position (EP), which is more reliable than a bare DR.
Despite the ubiquity of GPS, dead reckoning remains a critical skill and a mandatory STCW competency. SOLAS Chapter V requires that watchkeepers maintain continuous awareness of the vessel's position; when GPS is unreliable—in high-latitude polar waters, near GPS jammers, or during spoofing incidents—the DR plot on the chart or ECDIS provides the only means of safe navigation. IMO Resolution A.953(23) on the world-wide radionavigation system emphasises that no single electronic navaid should be relied upon exclusively, reinforcing dead reckoning as an indispensable discipline for every officer of the watch.