The National Institute of Standards and Technology (NIST) and the National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA), are taking collaborative action to provide national uniformity in the measurement of length.  A notice released by NIST announced the decision to deprecate the use of the “U.S. survey foot” on December 31, 2022.  After that date, the “U.S. survey foot” will be superseded by the “foot” (formerly known as the “international foot”), which is already in use throughout the U.S.

This action is designed to establish national uniformity in length measurements based on the foot.  For more than sixty years, two nearly identical definitions of the foot have been in use in the U.S. for geodetic and land surveys.  A Federal Register notice published on July 1, 1959 (24 FR 5348) by the National Bureau of Standards (renamed the National Institute of Standards and Technology in 1988) and the U.S. Coast and Geodetic Survey (reorganized as the National Geodetic Survey under the National Oceanic and Atmospheric Administration in 1970) refined the definition of the yard in terms of the International System of Units (SI), commonly known as the metric system.  The 1959 notice was issued after an international agreement among six nations resolved a long-standing difference in the relationship of the U.S. yard to the British yard.  The notice reported that there was a slight difference (2 parts per million) between the 1959 definition (i.e., one yard = 0.914 4 meter, exactly) and an 1893 definition (i.e., 1 yard = 3600/3937 meter, or approximately 0.914 401 83 meter).

The 1959 Federal Register notice then adopted a revised value for the foot for use throughout the U.S., and identified it as the “international foot” to show that it corresponded with the foot in use by the United Kingdom and other countries.  The notice defined this international foot as 0.304 8 meter (e.g., equal to 0.999 999 8 of the value for the foot officially adopted in 1893).  Additionally, to avoid disrupting the surveying practices at the time, the notice established an interim approach that permitted the limited use of the historic 1893 value of the foot exclusively in the field of geodetic surveys.  It was identified as the U.S. Survey Foot with the defined value of 0.304 800 61 meter (approximately).  The 1959 notice specifically stated that the U.S. Survey Foot should be used “until such a time as it becomes desirable and expedient to readjust the basic geodetic survey networks in the United States, after which the ratio of a yard, equal to 0.914 4 meter, shall apply.”  Although the use of the U.S. Survey Foot was intended to be an interim measure, its use continues to be prevalent in land surveying and mapping in much of the U.S.

The only practical solution is to deprecate the U.S. Survey Foot” and to require that its use in surveying, mapping, and engineering be discontinued.  Allowing the continued use of two definitions of the foot undercuts the value and benefit of national uniformity and allows for additional opportunities for confusion and unnecessary costs to the users, the States, and professionals in the surveying, mapping, and engineering fields.  No compelling justification to maintain two definitions for the foot exists.