Category: Off Topic and Test Posts
Shamelessly ripped from wiki
US inch was 25.4000508
UK inch was 25.399977
In 1930, the British Standards Institution adopted an inch of exactly 25.4 mm. The American Standards Association followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,[35][36] effectively endorsing Johansson's pragmatic choice of conversion ratio.[32]
In 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144 metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951;[37][38] the United States on 1 July 1959;[39][40][41] Australia in 1961,[42] effective 1 January 1964;[43] and the United Kingdom in 1963,[44] effective on 1 January 1964.[45] The new standards gave an inch of exactly 25.4 mm, 1.7 millionths of an inch longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch.[46][47]
US survey inches
The United States retained the 1/39.37-metre definition for surveying, producing a 2 millionth part difference between standard and US survey inches.[47] This is approximately 1/8 inch per mile; 12.7 kilometres is exactly 500,000 standard inches and exactly 499,999 survey inches. This difference is substantial when doing calculations in State Plane Coordinate Systems with coordinate values in the hundreds of thousands or millions of feet.
In 2020, the National Institute of Standards and Technology announced that the U.S. survey foot would "be phased out" on 1 January 2023 and be superseded by the international foot (also known as the foot) equal to 0.3048 metres exactly, for all further applications.[48] This implies that the survey inch was replaced by the international inch.
What a mess.
Then the Scots & French (anything but the English way) had different ideas.
