[time-nuts] Measurements

[Sanjeev Gupta]

On Sat, Aug 22, 2009 at 15:19, Ulrich Bangert <df6jb at ulrich-bangert.de>wrote:

>  Which in turn lead to the invention of a new class of surveyor
> instruments, which in turn enabled the French to measure the distance from
> the equator to the north pole (assumed to be 1/4 of the circumference) with
> a precision that must be admired even from a today point of view. I do not
> know the english term for it but in German these instruments are called
> "Repetitionskreis". You can find a pictue of one here:
>
>
> http://www.bistumsmuseen-regensburg.de/html/ausstellungen_moenche_repetition
> skreis.htm<http://www.bistumsmuseen-regensburg.de/html/ausstellungen_moenche_repetition%0Askreis.htm>
>

That sounds like the Repeating Theodolite, used for the survey from Dunkirk
<-> Paris <-> Barcelona

http://en.wikipedia.org/wiki/Repeating_circle

The basic idea is to mark out repeatedly the angle to be measured, but
actually measure the sum, _only_ at the end, which you then divide.  It
gives you the arithmetic mean of the value directly.  The major advantage
over doing this mechanically, rather than adding it up in your notebook, is
a that you have reduced the least-count of your graduated scale.


-- 
Sanjeev Gupta
+65 98551208     http://www.linkedin.com/in/ghane