dead reckoning

a way to calculate an exact location


dead reckoning = Koppelnavigation (koppeln) — eine Methode zur Berechnung der Position eines Schiffes oder Flugzeugs, die ausschließlich Informationen über die Richtung und Entfernung verwendet, die es von einem bekannten Punkt zurückgelegt hat.



“Using the magnetic compass and a process of ‘DEAD RECKONING’ whereby the ship’s position would be calculated by plotting speed and direction each day starting from a known location, Christopher Columbus (1451-1506) landed at the Bahamas (off the south-east coast of Florida) in October 1492.”


Did you

dead reckoning
noun phrase

- a way of calculating the position of a ship or aircraft using only information about the direction and distance it has travelled from a known point

- in navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading (or direction or course), and elapsed time

- the determination without the aid of celestial observations of the position of a ship or aircraft from the record of the courses sailed or flown, the distance made, and the known or estimated drift

Cambridge Dictionary / Wikipedia / Merriam-Webster


The term “dead reckoning” — the ascertaining of the position of a ship by “measurement of the distance run" (without observation of heavenly bodies) — is from the 1610s, from the nautical abbreviation “ded.” which means "deduced" in log books.


Ernest Shackleton's infamous Endurance expedition to cross Antarctica turned into a harrowing fight for survival after their ship became trapped and crushed by pack ice in 1915. With their vessel lost, Shackleton and his crew were stranded on the frozen Weddell Sea, hundreds of miles from civilization and any potential rescue.

Their only hope was to reach the remote Elephant Island, and from there, attempt a daring 800-mile journey across the treacherous Southern Ocean to seek help at the whaling stations on South Georgia Island. To navigate this perilous voyage in one of the expedition's small lifeboats, Shackleton relied heavily on the exceptional navigation skills of his captain, Frank Worsley.

Worsley, a skilled Antarctic navigator, employed the centuries-old technique of dead reckoning to chart their course. Without modern navigation aids like GPS, he meticulously tracked their boat's speed, heading, and distance traveled using only a compass, log line, and timepiece. By continuously updating their position based on these observations, Worsley could estimate their location relative to their intended destination.

Navigating through storms, blizzards, and icy seas in a 22-foot boat, Worsley's dead reckoning calculations proved invaluable. His keen sense of direction and ability to account for currents, winds, and other factors ensured they stayed on course, avoiding being swept off into the vast, unforgiving expanse of the Southern Ocean.

After an incredible 16-day journey across some of the most treacherous waters on earth, Worsley's navigation skills paid off. They miraculously reached the remote shores of South Georgia Island, from where a rescue party could be organized to retrieve the remaining men stranded on Elephant Island.

Shackleton's unwavering leadership and Worsley's masterful navigation using dead reckoning ensured that not a single life was lost during this incredible ordeal. Their feat remains one of the greatest stories of survival and navigation prowess in the annals of polar exploration.


- as dead as a dodo (or doornail) = completely lifeless, utterly gone

- a dead ringer = an exact duplicate

- a dead end = a situation with no way out

- a dead zone = an area with no internet connection

- the dead of night = the very late hours

- dead common = very ordinary, nothing special

- playing dead = pretending to be unconscious or dead

- the joke fell dead = the audience found it unfunny

- a dead cert (certainty) = something absolutely guaranteed to happen

- to die for = something incredibly good or desirable


- for the word “reckon”:

account, add up, adjudge, analogize, analyze, appraise, approximate, assess, assume, audit, balance, calculate, compute, count, deduce, determine, estimate, evaluate, examine, extrapolate, figure (out), forecast, foresee, foretell, gauge, get(have) a handle on something, guess, guesstimate, infer, measure, postulate, prognosticate, project, puzzle out, quantify, rate, rationalize, reason (out), RECKON, surmise, take account of, work out

SMUGGLE OWAD into an English conversation, say something like:

“If you want to deep-dive, check out Jim Bennett’s fascinating book ‘Navigation’, which has a whole chapter dedicated to DEAD RECKONING.”

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