[GTALUG] Surveying

[Lennart Sorensen]

On Fri, Apr 22, 2016 at 10:31:32AM -0500, o1bigtenor wrote:
> Would really like to know where this information comes from - -
> do you have any references?

As per wikipedia (with references to NIST):

The international yard and pound are two units of measurement that
were the subject of an agreement between six nations signed on 1 July
1959. The six nations were the United States, the United Kingdom, Canada,
Australia, New Zealand and South Africa. The agreement defined the yard
as exactly 0.9144 meter and the pound as exactly 0.45359237 kilogram

https://en.wikipedia.org/wiki/International_yard_and_pound

Before this things had different values in different placs and changed sometimes.

The UK made the yard be 0.914399204m in 1897, which is rather close to
0.9144m that it is now.

The UK went to one inch = 25.4mm in 1930, the US in 1933, and many more
countries in 1935 and the treaty in 1959 made the yard and inch officially
0.9144m and 25.4mm respectively in a number of countries.

Specific change in value (from https://en.wikipedia.org/wiki/Inch):
This resulted in the internationally accepted length of the imperial
and US customary inch being exactly 25.4 millimetres. The international
inch is 1.7 millionths of an inch longer than the old imperial inch,
and 2 millionths of an inch shorter than the US inch.

-- 
Len Sorensen