[GTALUG] Surveying

[o1bigtenor]

On Fri, Apr 22, 2016 at 11:02 AM, Lennart Sorensen
<lsorense at csclub.uwaterloo.ca> wrote:
> 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.
>
OK - - - so these are part of the rule changes from the late 50's. Its also
when it went from NC and NF to UNC and UNF and there are lots of
companies AND people that still use the old designation.

Rule changes this old shouldn't really be a problem for today's use though.

Regards

Dee