[time-nuts] OT Prototype Boards

[Jim Palfreyman]

Oh dear. Please go metric US. Please.

We will help you.

Jim



On 27 June 2013 11:33, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> 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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