Having two versions of the foot has created problems, reported the American Society of Civil Engineers (ASCE) recently. The difference between the two versions is very, very small: the international foot is shorter, which means that a mile is around one-tenth of an inch (2.5mm) shorter than a mile measured by the survey foot. Translated over a longer distance would mean that the east-west length of the US would be longer by 30ft (9.14m) when measured by the international foot.
The differences may be considered negligible, but the National Institute of Standards and Technology (NIST) and the National Oceanic and Atmospheric Administration (NOAA) think otherwise and are preparing to act. According to NOAA, the difference between the two systems can adversely impact activities such as engineering, surveying, mapping and other sectors which depend on accurate positioning. This difference is particularly important when translating geographical co-ordinates from metres to feet and, depending on which foot is used, could give two very different coordinates.
At present, around half of all US states mandate use of the survey foot. They will have to fall in line at the beginning of 2023 when the change is due to come into force, although a full transition is expected to take several years longer.
The initiative has prompted some to call for the abolition of imperial measurements in favour of the metric SI system.
