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

Attila Kinali attila at kinali.ch
Tue Jan 24 06:16:42 EST 2012


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?
> 
> Back then the stars were the coordinate system and the position of
> the telescope the unknown, so you did it by observing stars with
> documented coordinates with your new telescope and then you set
> your clock and calculated your lattitude accordingly.
> 
> Remember: back then longitude and time were as single convolved coordinate.

That's what i'm aiming at. Yes, the lattitude can be calculated
using angle measurements relative to a known horizontal plane (mercury
mirror) or a vertical line (plumb bob). Still not easy to get below
an arc minute, but doable. 

But how do you untangle longitude and time? How do you know that you
are looking exactly south (or north)?

			Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin




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