On Jan 18, 12:54 pm, John Schilling <schil...@[EMAIL PROTECTED]
> wrote:
> On Thu, 17 Jan 2008 20:43:02 +1100,bernardZ<Berna...@[EMAIL PROTECTED]
> wrote:
> >In article <5krto31abrdlh9mcti2o8d0u32op62g...@[EMAIL PROTECTED]
>,
> >schil...@[EMAIL PROTECTED]
says...
> >> Dead reckoning is *not* an accurate navigational technique. Not to
> >> within one percent, not even to within ten percent. Dead reckoning
is
> >> what you use between visual or celestial fixes, to minimize the error
> >> that accumulates between points where you actually do know where you
> >> are.
> >It was the most accurate available
>
> In the sense that mercury was the most effective treatment available
> for syphillis, yes.
>
Indeed.
> >and using it European sailors went all round the world for example
Drake.
>
> Actually, Drake was somewhat famous for his effective use of celestial
> navigation.
>
(a)
If you check you will see that Drake could only do it on land and he
was rare that he could do it. Also celestial navigation at sea at the
time could not give you longitude, it could give you latitude if you
knew what you were doing but few navigators of the period did. Once
at sea he was on DR.
> >It was also used by the Dutch to go to Japan and the East Indies.
>
> They mostly used a combination of celestial navigation and pilotage.
>
I would agree with the pilotage part. See (a) above
> >It took a lot of effort to do, required trained people
>
> The physicians, surgeons, and alchemists of the age were also quite
> well trained, and put a great deal of effort into their crafts.
>
Which was my point that the people using DR required a lot of skill
too.
> >and was replaced by better methods in the 1800s.
>
> No; it was replaced by better methods in the *15*00s. Specifically,
> the use of the astrolabe, octant, and cross-staff to measure and track
> celestial latitude. This was SOP for virtually all oceanic navigators
> by 1600, and it was vastly superior to dead reckoning.
>
see (a) above
These can be useful in the Atlantic and it can help to get you around
the Cape of Good Hope if you have DR however to get to the East Indies
or Japan using celestial navigation you require longitude.
Even much later after a massive amount of astronomical research was
done this proved impractical on a ship. This problem was finally
solved by John Harrison with his clock but all this is later.
> >Now let me read to you what mcv <mcv...@[EMAIL PROTECTED]
> wrote that sparked
> >this debate off.
> >++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >While reading Asimov's _Second Foundation_, the book proudly described
> >a really clever system that made it really easy for relatively
untrained
> >people to figure out exactly where in the galaxy they are. Before the
> >invention of that item, figuring out your location took days or weeks,
> >but all I was thinking was: if this process is this simple, why the
> >hell isn't it automated in the first place?
> >+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >Now what exactly are you objecting too?
>
> I am objecting to your persistent attempts to describe dead reckoning as
> an accurate navigational technique, to credit the successes of
navigators
> like e.g. Drake to dead reckoning, and to grossly exaggerate the
successes
> of actual dead-reckoning navigators like e.g. Columbus.
>
> *Whatever* inspired you to make those claims, they are in fact all
wrong.
>
I suppose it depends on your definition of accurate the reality is
that it worked just like it did in the Asimov's Foundation series.
Even in modern times it is taught and used.
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