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http://dictionary.reference.com/browse/dead

Dead reckoning may be from nautical abbreviation ded. ("deduced") in log 
books, but it also fits dead (adj.) in the sense of "unrelieved, absolute."


http://en.wikipedia.org/wiki/Dead_reckoning

Dead reckoning is navigation without stellar observation. With stellar 
observation, you are "live," working with the stars and the movement of the 
planet. With logs, compasses, clocks, but no sky, you are working "dead."


http://www.straightdope.com/columns/read/2053/is-dead-reckoning-short-for-deduced-reckoning

One theory, supported by the OED, is that it's dead in the sense 
"complete(ly)" or "absolute(ly)," also found in "dead wrong," "dead ahead," 
"dead last," etc. The idea seems to be that the dead-reckoning position is 
one based completely on reckoning (calculation) and not at all on observation 
of landmarks. Others hold that "dead" means "unmoving," as in "dead in the 
water." The idea here is that dead reckoning is calculated with respect to an 
object (like the log) that is dead in the water (not moving with respect to 
the surface of the water). Yet another theory is that it comes from "dead 
seas" (supposed to mean "unknown seas"), where dead reckoning would be an 
important tool.

--
GregR



--- On Sun, 1/11/09, frankreed@HistoricalAtlas.com  wrote:

> From: frankreed@HistoricalAtlas.com 
> Subject: [NavList 7003] Ded and Dead
> To: NavList@fer3.com
> Date: Sunday, January 11, 2009, 8:04 PM
> A couple of months ago, I noted that the etymological story
> saying that "dead reckoning" should really be
> "ded reckoning" (derived from 'deduced
> reckoning') is more common among flying navigators than
> floating navigators. I've been collecting bits and
> pieces on this over the past few months, and it does still
> seem to be true that navigators in aviation repeat this
> explanation more often than marine navigators. Also, people
> who work on autonmous navigation/robot navigation also seem
> to repeat this "etymology." Just a difference in
> culture...
> 
> I've tracked down what appears to be the earliest
> version of this explanation of "dead reckoning". I
> have found no cases before 1920 (and that also could explain
> why aviators picked this up since long-distance air
> navigation had its origins very close to this date). I could
> not find the original article, but this one appears to quote
> it verbatim:
> 
> From "The Rudder" Jan. 1920
> "In every ship's log, in all books of instruction,
> in all works on navigation, and in innumerable other
> publications, we find a special point made of the "dead
> reckoning" on board ship. Why dead? It has been for a
> century or more a stumbling block to investigators, and, as
> Daniel Defoe would have said, "lexicographers have gone
> astray in this unknown channel." One after another has
> attempted to arrive at some reasonable explanation of it,
> but has had to abandon the task as hopeless, for when they
> have marshalled all the facts at their disposal it is always
> found that the operations which the word covers are anything
> but dead. They are, indeed, very much alive! 
> 
> Henry Harries, acting marine superintendent meteorological
> office, thus explains the phrase in the London Morning Post:
> "It was not until nearly the close of the Eighteenth
> century that printed log books were supplied by the
> Admiralty. Long before that officers were compelled to keep
> a journal, the form of which was only gradually developed.
> Originally it was on loose sheets of small size, and the
> columns, when introduced, had to be ruled by hand. The log
> of the Dreadnought, 1679, had twelve very narrow columns on
> a page. For want of space the column for the latitude,
> 'deduced from the reckoning,' as Riddle has it, was
> headed Ded. Latt. "This abbreviation Ded., for
> 'deduced,' has become corrupted into dead, which has
> for generations served to exercise in vain the most learned
> savants on two continents to get at its real and in the
> result perfectly simple meaning. There is not a mariner who,
> on reading this explanation, will fail to realize that
> deduce is the only word which correctly expresses the method
> of obtaining his so-called dead reckoning. He deduces his
> position from the account he has kept, just as any tradesman
> deduces his profit or loss from his account." "
> 
> There are a couple of problems with HH's theory. First,
> the spelling "ded" for "dead" was not
> unusual in the 17th century. English spelling was not yet
> standardized (or is it standardised?). Second, there are
> early 18th century nautical dictionaries that say "dead
> reckoning" and make no mention at all of some earlier
> spelling or a derivation from "deduced reckoning".
> That would be very hard to account for considering the few
> decades that had elapsed since HH's logbook evidence.
> Also, he mentions the phrase "deduced from the
> reckoning" which is found in many 19th century
> navigation manuals. Unfortunately for the theory, this
> phrase was *never* used as a synonym or a replacement for
> dead reckoning. It's not relevant to the origins of the
> phrase. The real etymology is mostly irrelevant today... I
> can imagine something about calculating as if in "dead
> water" (without currents). But I suppose the phrase
> thrived for generations because it's a bit of comedy:
> when you're "dead", you'll face your
> "reckoning" (i.e. judgement). Puns have legs.
> 
> -FER
> 
> 
> 
> 
> 

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