[time-nuts] OT Prototype Boards

[Hal Murray]

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.[

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