The definition of the foot was updated in 1959 in the United States, but a previous definition of the foot is still in use and has caused confusion over time. The legally defined “international foot” and the older “U.S. survey foot” differ by only 0.01 foot per mile.
However, having both definitions in use often has resulted in confusion in surveying and mapping where computing accurate coordinates over large distances are commonly required. Retiring the U.S. survey foot will eliminate this confusion, and after 2022 the international foot will simply be called the foot. Read more on the NIST website.
The modernization of the National Spatial Reference System (NSRS) in 2022 is the perfect time to move the United States toward a single, uniform definition of the foot. Both NOAA and NIST have decided to deprecate the US foot through two co-issued Federal Register Notices, and by conducting public outreach.