Talk:Dead reckoning

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I think this article ought to be at Dead reckoning (which redirects here, but has something in the history, so I can't move it myself), which appears to be a far more common spelling for the same thing. However, as I don't know anything about the subject myself, and they might be different things for all I know, I won't do anything about it just yet. --Camembert

Ded reckoning is the older spelling, emphasizing the "deduced". But my Chapman's Seamanship and Bluejacket's Manuals spell the process "dead", so I'll make that change. --GABaker

To add to the confusion, Bowditch says:

... The expression dead reckoning probably originated from use of the Dutchman's log, a buoyant object thrown overboard to determine the speed of the vessel relative to the object, which was assumed to be dead in the water. Apparently, the expression deduced reckoning was used when allowance was made for current and wind. It was often shortened to ded reckoning and the similarity of this expression to dead reckoning was undoubtedly the source of the confusion that is still associated with these expressions.

Reference: Pub No. 9: American Practical Navigator, Vol. 1, (1984 edition). by Nathaniel Bowditch. DMA stock no. NVPUB9V1. p. 59. --Dairiki

Thanks, Dairiki. I think we need to put in an explanation of how this came to be. And do we have enough articles on seamanship? ----GABaker

We never have enough articles on anything :-) --Camembert

NP. Perhaps a Seamanship page to tie it all together would be a good thing? --Dairiki

I started a Seamanship shell.------GABaker

There is an article dwelling into multiple sources (more than the dip into dictionaries below) at http://www.straightdope.com/mailbag/mdeadreckoning.html

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The phrase dead reckoning dates from Elizabethan times (1605-1615). The speculation, folk etymology, urban legend, sea cook's tale, or whatever you want to call it about "deduced reckoning" does not appear in any reputable dictionary -- Oxford English, Webster's Unabridged, Random House Unabridged, American Heritage, or Noah Webster's American Dictionary of the English Language from 1850, nor does it appear in Brewer's Dictionary of Phrase and Fable, nor in either of the standard etymological dictionaries I have here, Skeate's and Eric Partridge's. Nor does the expression ded reckoning appear in any of these sources. This just isn't so, entertaining though it may be.

Dead reckoning is navigation without stellar observation. With stellar observation, you are "live", working with the stars and the planet. With logs, compasses, clocks, but no sky, you are working "dead". No mystery here. Ortolan88 04:18 Oct 25, 2002 (UTC)

I think it's very likely that "dead" is used to mean "accurate", as in a "dead shot" or "dead right". Dave Gittins.

You also have the misspellings of the time. English orthography wasn't standardized for a while--nor was mine! --GABaker

dictonary.com has:

dead reckoning

n.

A method of estimating the position of an aircraft or a ship without astronomical observations, as by applying to a previously determined position the course and distance traveled since. Predictive calculation based on inference; guesswork.

[Possibly alteration of ded., abbr. of deduced, from deduce, to trace from the beginning. See deduce.]

But note, "possibly" -- Zoe

I will cheerfully put the least of my dictionaries up against dictionary.com any day. The "deduced" is a folk etymology. Ortolan88

The Oxford English Dictionary gives these quotes, dated 1613, 1760, 1840, 1891, 1917, and 1935:

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.

That dictionary does not give an etymology. Michael Hardy 18:22, 31 Oct 2003 (UTC)

The Swedish term is "död räkning" (dead calculation, dead counting). Note the similarity (and ethymological relationship) between the words räkning and reckoning. I guess "dead" means it is done "in the blind", not from "live" data. --LA2 04:20, 26 January 2006 (UTC)

According to www.garmin.com, the satellite navigator models Garmin StreetPilot 2650, 2660, and 7500 feature "dead reckoning capabilities, so you will continue to get navigation guidance even when GPS signals are obscured. To use this feature, a special dead reckoning cable must be connected to your vehicle's speedometer and backup lights [...]. Once installed, your StreetPilot will acknowledge your turns as well as your distance traveled when GPS reception is unavailable." Can anyone explain how it can detect turns by only sensing the speedometer? Doesn't that require a gyro or something? Can the built-in harddisk function as a gyro? --LA2 04:13, 26 January 2006 (UTC)

The earliest known reference, available from many ships' logs from the early 1700s, is that "dead reckoning" began as "deduced reckoning," which was recorded in the ships' logs as "ded. reckoning." It wasn't pronounced as "dude" reckoning, but as "dead" reckoning. Over time, it began to be spelled as "dead reckoning" rather than "ded. reckoning." However, the American Practical Navigator's reference to the floating object thrown into the water as being "dead" in the water holds merit, and is perhaps just as responsible for the term as is the abbreviation for the word "deduced." - Mugs 14:42, 7 January 2007 (UTC)

[edit] Stilted Language

I'm undertaking many edits to replace the rather stilted language with more modern terminology. Please bear with me until I'm fished. Shouldn't take more than two hours. - Mugs 13:43, 7 January 2007 (UTC)

[edit] Diverge Path Integration

Dead Reckoning is a mathematical process based upon scientifically measured inputs. Animals don't do math! "Path Integration" needs it's own topic space, not a disambiguation redirect to a process only humans perform. - Mugs 14:33, 7 January 2007 (UTC)

[edit] Aviation usage vs marine

Perhaps this article needs to have aviation and marine sections. I am not familiar with a DR at every 300 miles and combined turns etc, it must refer to aviation? Also as far as I know the term velocity is not commonly used in marine navigation, in physics velocity refers to both speed and direction. Generally in marine navigation a DR does not include set and drift, I don't know what the practice is in aviation, in marine usage a DR corrected for set and drift is called an estimated position (EP), KAM 01:36, 27 March 2007 (UTC)