[time-nuts] establishing your position w/o gps

[Azelio Boriani]

Maybe the Longitude Act was issued also because of the disaster occured in
1707 due to a navigation error: the Royal Navy fleet lost 4 of its 15 ships.

On Tue, Jan 24, 2012 at 5:50 PM, Azelio Boriani <azelio.boriani at screen.it>wrote:

> Yes, the first real push was the Longitude Act (1714) and the Harrison's
> clocks.
>
>
> On Tue, Jan 24, 2012 at 5:36 PM, Chris Albertson <
> albertson.chris at gmail.com> wrote:
>
>> On Tue, Jan 24, 2012 at 3:16 AM, Attila Kinali <attila at kinali.ch> wrote:
>> > On Tue, 24 Jan 2012 11:04:08 +0000
>> > "Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:
>> >
>> >> In message <20120124115848.312d60bd4fccce4f3e71c136 at kinali.ch>,
>> Attila Kinali w
>> >> rites:
>> >>
>> >> >All this talk about telling the time using stars or the sun made me
>> wonder
>> >> >how did people tell what position their telescopes had back in the
>> days
>> >> >before GPS?
>>
>> Sailingships and trade was what pushed this.   At the time of Columbus
>> he was able to know his latitude within a few 10s of miles but even
>> after returning to Europe he did no know how far around the world he
>> had sailed.  Was it 1/3rd or 2/3rds?  They had no way to know.    The
>> problem was that on one had a clock that should keep time well enough.
>>  They used hour glasses on board ship for short duration time keeping
>> but those were of no use on a longer ocean crossing.
>>
>> Later they discovered the idea of common view of the moons of Jupiter
>> and they could measure the time from local noon some even on Jupitor
>> while a person back home did the same thing.  Later when he got back
>> home they compare notes and then know the difference in longitude.
>>  Good ocean going clocks were still centuries away.    But in the
>> 1500's they could only know the location after the fact when they
>> returned
>>
>> --
>>
>> Chris Albertson
>> Redondo Beach, California
>>
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>
>