On Tue, 15 Jan 2008 21:46:50 -0800 (PST), bernardz <bernardz@[EMAIL PROTECTED]
>
wrote:
>On Jan 16, 11:55 am, John Schilling <schil...@[EMAIL PROTECTED]
> wrote:
>> On Sun, 13 Jan 2008 16:45:42 -0800 (PST),bernardz<berna...@[EMAIL PROTECTED]
>
>> wrote:
>> >> > Why?
>> >> > In the days of sailing ****ps to navigate you used dead reckoning.
It was
>> >> > accurate. However it took much work.
>> >> Right, because in the open ocean, dead reckoning works really well.
>> >It work well if you know what you are doing and that is how it was
>> >done for centuries. It just takes a lot of work.
>> >What the later medieval and early modern sailors did was every hour
>> >they measured the speed and direction (with a compass) of the ****p.
>> >They then recorded these figures on a board. Every so often these
>> >figures were transfered to a chart by the navigator.
>> >You may find this article interesting.
>> >http://www.newworldexplorersinc.org/EarlyNavigation.pdf
>> Interesting indeed. Second paragraph:
>> "By the late fifteenth century, dead reckoning navigation had been
>> refined to the point that Columbus and other competent navigators
>> were making long ocean passages to the new world and return with
>> skill and accuracy".
>> This would be the "competent navigator" who was consistently off
>> by two continents and an ocean? OK, maybe competent navigator but
>> incompetent geographer. That's possible.
>In the article it states
>++++++++++++++++++++++++++++++++
>The historian Andres Bernaldez, a friend and confidant of Columbus,
>confirmed this accuracy of dead-reckoning navigation of the period
>when he re****ted that: A good pilot or master is not considered such
>if, in traveling over a great distance from land to land, out in the
>open sea with no indication of any land, he is off by ten leagues even
>when the trip is a thousand leagues long.
>++++++++++++++++++++++++++++++++++++
>So we are looking at about 1% error.
Or an unreliable narrator; Bernaldez wouldn't be the first nor the last
"friend and confidant" of a historical figure to exaggerate his buddy's
virtues by a few orders of magnitude.
But if Bernaldez was right, then Columbus can not be considered a "good
pilot or master". On Columbus's return from his first trip to America,
he made landfall in the ****tugese-owned Azores rather than the Spanish
Canary Islands, an error of roughly three hundred leagues in a trip a
thousand leagues long. And one which almost got Columbus arrested as
a spy or pirate. On Columbus's second trip to America, he aimed for
Hispaniola and made landfall at Dominica, which is off by two hundred
leagues in a trip a thousand leagues long.
So, since Columbus wasn't within an order of magnitude of being a
"good pilot or master", could you give us the names of some 15th-century
captains who *were*? Ones who are recorded as actually having made
landfall within ten leagues of their intended destination on an honest
thousand-league voyage? Ones whose logs don't need to be retconned
with modern navigational technique to re****t positions accurate to
within one percent?
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 ac***ulates between points where you actually do know where you
are.
And if the next celestial fix is a hundred years in the future on
account of the ***tant not having been invented yet, you'd best be
aiming at an entire continent, and even then I'm not selling you
any sort of insurance.
--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
*John.Schilling@[EMAIL PROTECTED]
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *
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