Definition
To navigate by calculating your present position from a known starting point using your heading, airspeed, wind, and elapsed time, without reference to external navigation aids or visual landmarks.
Plain English
To work out where you are by tracking the direction you've been flying, how fast, and for how long, starting from a place you knew for certain.
Context Anchor
Seen in navigation discussions, especially when there is a gap or loss in GPS, radio navigation, or other position information.
Derivation
From the older nautical phrase 'deduced reckoning,' often shortened in logs to 'ded. reckoning,' which over time was heard and written as 'dead reckoning.' 'Reckon' simply means to calculate or work out. It helps to remember the word is about deducing your position from known facts, not about anything being 'dead.'
Why Pilots Care
If your GPS or navigation radios fail, dead reckoning is one of the basic skills that lets you keep flying safely toward a known point until you can re-establish position with a chart or visual landmark.
Grounding Statement
Start with your last confirmed position, then carry your motion forward using time, direction, speed, and wind.
Intuition Check
Do not read “dead” as meaning the aircraft, engine, or equipment has failed. In this term, dead reckon means to calculate an estimated position from movement since the last known position.
Example Sentence 1
With the GPS unit failed, the pilot dead reckoned from the last known checkpoint using heading, airspeed, and the forecast wind.
Example Sentence 2
After losing GPS, the crew began to dead reckon their position by timing the leg and holding a constant heading.