[time-nuts] Measurements

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 22 09:33:22 UTC 2009


Sanjeev Gupta wrote:
> 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.

Cool. I completely understands it yeat, it was new to me. So now I know 
what I learned today.

Thanks Sanjeev!

Cheers,
Magnus



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