[time-nuts] OT Prototype Boards

[J. Forster]

The same issue arises with old callendars. What always happens is the old
units are converted to the current standard. You never see a LASER
wavelength in barlycorns.  The current definitions are used and backward
corrected.

-John

==============

>
> jfor at quikus.com said:
>> There WERE (past tense) a number of definitions of the inch, ranging
>> from
>> lines on bars of PtIr to a string of grain kernels.
>
>> Now there IS (present tense) one, defined as 2.54 cm.
>
> Except...
>
> http://en.wikipedia.org/wiki/Foot_%28unit%29#International_foot
>
> When the international foot was defined in 1959, a great deal of survey
> data
> was already available based on the former definitions, especially in the
> United States and in India. The small difference between the survey and
> the
> international foot would not be detectable on a survey of a small parcel,
> but
> becomes significant for mapping, or when the state plane coordinate system
> is
> used in the US, because the origin of the system may be hundreds of
> thousands
> of feet (hundreds of miles) from the point of interest. Hence the previous
> definitions continued to be used for surveying in the United States and
> India
> for many years, and are denoted survey feet to distinguish them from the
> international foot. The United Kingdom was unaffected by this problem, as
> the
> retriangulation of Great Britain (1936-62) had been done in meters.
>
> The United States survey foot is defined as exactly 1200/3937 meter,
> approximately 0.3048006096 m.[
>
> --
> These are my opinions.  I hate spam.
>
>
>
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