ET would not be happy with a "foot".
Our English foot has not been so constant. The U. S. Congress legalized the use of the metric system in 1866 on the basis that one meter is exactly equal to 39.37 inches. In 1959 a number of English-speaking countries agreed that an inch is exactly equal to 2.54 centimeters so that the International foot is exactly equal to 0.3048 meters. The United States retained the old 1866 equivalency and called it the U. S. Survey foot so that 1 U. S. Survey foot equals 1.000002 International feet.