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From: Trevor J. Kenchington (no email)
Date: Sun Nov 07 2004 - 20:21:51 EST
Alexandre,
You wrote:
>>Voyagers like the Polynesians,
>>for example, who roamed the Pacific seas with
>>"no sextant, no watch, no
>>almanac, nothing",
>>
>
> I suppose they also did not have compass, so DR
> was not available to them, and they had to rely
> on CelNav entirely.
That is a false distinction. They used the stars (and other guides) to
determine direction -- call that CelNav if you wish. But on the basis of
such a "star compass", they then maintained a dead reckoning in the
sense of holding a known course for a known time at an estimated speed.
> So I would be interested to know
> more details on how exactly they did it.
Start with Steve Thomas' "The Last Navigator". It is an autobiographical
account of his own training in the techniques and the thought patterns
that go with them. Anyone who starts with Thomas' prior knowledge of
Western navigation methods should be able to comprehend the Polynesian
(strictly Micronesian) methods.
> It is easy to imagine for me how they determine latitude.
> What is really hard to imagine, that they could determine
> longitude by their Cel Nav methods, even roughly.
Without either chronometers or lunar predictions, I don't see how anyone
would get longitude by celestial methods. And neither of those were
available before Western technology achieved them in the mid-18th Century.
>>An almanac just happens to be one of _our_ ways of
>>passing on this sort of information.
>>
>
> I disagree with "just one":-)
> Based on what I know, it is also a "better", "superior"
> way in comparison with what other cultures invented.
> In the sense that it gives better precision.
> Of course one can argue that other cultures did not need
> better precision for their needs, with this I don't argue.
> (Correct me if I am wrong here).
Better precision, of course, but at a considerable cost. Long after the
sextant/chronometer/almanac/sight-reduction-tables technology package
diffused around the world, the great majority of vessels pushing out
from shore did not (and do not) carry that package. I very strongly
suspect that, at any time you care to name, the great majority of
vessels (by numerical count) going out of sight of land have done so
without that package of technology. I would suggest that that indicates
that the package is not "better" overall for many potential users. An
almanac, clearly, has little to recommend it as a way of encapsulating
celestial lore for anyone who does not also carry a sextant or some
equivalent instrument.
So better precision, of course. But "better"? I'd not be so sure.
Trevor Kenchington
--
Trevor J. Kenchington PhD
Gadus Associates, Office(902) 889-9250
R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251
Nova Scotia B0J 2L0, CANADA Home (902) 889-3555
Science Serving the Fisheries
http://home.istar.ca/~gadus
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