JAXAshby wrote:

hoary, you quote phonetic spellings of ancient words. "dead" is exact, "ded"
is deduced.

The following of some of the definitions of the word "dead" and each shows
why
the word is not used in the context of the guestimated, vague navigation
called
Ded(uced) Reckoning:

Exact; unerring. the dead center of a target

Absolutely; altogether: You can be dead sure of my innocence.

Directly; exactly: There's a gas station dead ahead.

[In golf], a ball is said to lie dead when it lies so near the hole that
the
player is certain to hole it in the next stroke.

Dead ahead (Naut.), directly ahead; -- said of a ship or any object, esp.
of
the wind when blowing from that point toward which a vessel would go.

Dead Center (Mach.), either of two points in the orbit of a crank, at
which
the crank and connecting rod lie a straight line. It corresponds to the end
of
a stroke; as, A and B are dead centers of the crank mechanism in which the
crank C drives, or is driven by, the lever L.

Dead heat, a heat or course between two or more race horses, boats, etc.,
in
which they come out exactly equal, so that neither wins.

unerringly accurate; "a dead shot"; "took dead aim"

sudden and complete; "came to a dead stop"

completely and without qualification; used informally as intensifiers; "an
absolutely magnificent painting"; "a perfectly idiotic idea"; "you're
perfectly
right"; "utterly miserable"; "you can be dead sure of my innocence"; "was
dead
tired"; "dead right"


well, maybe those who don't know the meaning of the word "dead" might use
it in
some weird fashion, but they don't count.


While "ded" reckoning is proper usage, so is "dead" reckoning:

dead reckoning.

The estimation of a ship's position from the distance run by the log and
the courses steered by the compass, with corrections for current,
leeway, etc., but without astronomical observations. Hence dead latitude
(q.v.), that computed by dead reckoning.

1613 M. Ridley Magn. Bodies 147 Keeping a true, not a dead reckoning of
his course. 1760 Pemberton in Phil. Trans. LI. 911 The latitude
exhibited by the dead reckoning of the ship. 1840 R. H. Dana Bef. Mast
xxxii. 124 We had drifted too much to allow of our dead reckoning being
anywhere near the mark. 1891 Nature 3 Sept., The log, which for the
first time enabled the mariner to carry out his dead-reckoning with
confidence, is first described in Bourne's ‘Regiment for the Sea’, which
was published in 1577. 1917 Bosanquet & Campbell Navigation for Aerial
Navigators i. 4 In aerial navigation+Dead Reckoning is the position
arrived at as calculated from the estimated track and the estimated
speed made good over the ground. Ibid. 5 These data enable us to find a
Dead Reckoning position. 1935 C. G. Burge Compl. Bk. Aviation 477/1
Dead reckoning+is a compromise between pilotage and navigation. 1868
Lowell Witchcraft Prose Wks. 1890 II. 372 The mind, when it sails by
dead reckoning+will sometimes bring up in strange latitudes.


None of these sources, Jax, have your knowledge of navigating the
world's great oceans in a clapped-out little 26' daysailer, as you
do...but, nonetheless...


Nice try, dipstick, but the sources I quoted are quite real, unlike the
imaginary gremlins that occupy your synapses. Ded or Dead is proper. If
you want to compare your education in and experience with etymology to
mine, why, you go right ahead. My master's degree in English is really
in etymology, and, as part of the requirements, I worked for two
semesters as an editor and project director of the National Union
Catalog, a project that involved alphabetizing and organizing the entire
card catalogue of the Library of Congress.

The definition I posted is from the second edition of the OED. There's
no knowledge you have that trumps the OED.