I new that U.S. had two foot measurement units.  I did not really know or cared about the difference.

U.S. Survey foot dating from the 19th century is slightly longer than the internationally accepted foot from 1959. NYT says the difference is " two feet for every million feet".

It is not much. But enough to create confusions in tunnel constructions and other works.

As of Jan. 1, 2023, U.S. will stop using the U.S. Survey foot. From then on, the international foot will be the only foot the US will be using.

For a comprehensive and entertaining coverage, follow this link:

https://www.nytimes.com/2020/08/18/science/foot-surveying-metrology-dennis.html