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Dead reckoning

Posted by Donald C Cook on July 30, 2005

In Reply to: Dead reckoning posted by R. Berg on July 30, 2005

: : : In the explanation for the origin of the phrase "dead ringer" it is noted that :

: : : "Dead, in the sense of lifeless, is so commonly used that we tend to ignore its other meanings. The meaning that's relevant here is exact or precise. This is also the sense it is used in the term 'dead reckoning'."

: : : I was given to understand that the orinal phrase was rather "ded reckoning" which was an abbreviated form of "deduced rekconing" a nautical term for estimating position by use of speed, elapsed time and direction to "deduce" a vessel's position. I cannot remember the source; am I totally wrong about this origin?

: : I don't know. Interesting theory. The previous discussion of the phrase is at bulletin_board 3 messages 420.html

: Forget the "deduced" explanation. The Oxford English Dictionary has a separate entry for "dead reckoning" as a phrase. That entry refers to the sense of "dead" defined as "unrelieved; unbroken; absolute; complete; utmost." (Return to ESC's post for the link to a previous discussion.)

I do not think "[f]orget[ting] the 'deduced' explanation" will serve. As I believe, Oxford is landlocked but for the Thames, and perhaps ought to be a secondary source for information maritime such as the derivation of "dead reckoning".

In the U.S. we have had an organization since the beginning of the 20th which publishes a handbook called, "Piloting and Seamanship". It referred to the "deduced" lineage many decades ago, in my own recollection.

Militating to the correctness of this explanation is the fact that the Oxford cites "absolute; complete; utmost" as the sense of "dead reckoning", which is plainly in error: dead reckoning is in fact imprecise, and is a method of shorewise navigation without the use of tools such as a sextant. It uses assumptions, probabilities and guesses as a basis for arriving at a probable position for a vessel.

That is not to say that it is unreliable. Dead reckoning was used by many, including myself, before the advent of more precise tools such as GPS.

As the Oxford Dictionary ascribes a level of precision to dead reckoning which it has never owned, and there are other sources which ought to be expected to know what they are talking about, I submit it is in error in its description of the lineage of "dead reckoning".