NB_210_23_2 - NB 210-23-2 ENG – Redefinition of U.S. Survey Foot
NB 210-23-2 ENG – Redefinition of U.S. Survey Foot
National Bulletin: 210-23-2  
Date: November 18, 2022 
Subject: ENG – Redefinition of U.S. Survey Foot 

Purpose.  To provide clarity on the “foot” as the basic unit of measure.   
Expiration Date.  September 30, 2023  
Background.  Since 1893, the legal definition of the foot in the United States has been based on the meter. The definition adopted at that time was the one specified by Congress in 1866, as 1 foot = 1200/3937 meter (exactly), or 1 foot = 0.3048006 meter (approximately).

In 1959, the relationship of the foot to the meter was officially redefined as 1 foot = 0.3048 meter (exactly). The 1959 redefinition of the foot was legally binding and intended for the entire United States, but a single exception for geodetic surveying temporarily allowed continued use of the 1893-foot definition. To distinguish between these two versions of the foot, the 1959 version was named the “international foot” and the 1893 version the “U.S. survey foot.”
This situation has led to confusion and errors that continue to this day.       
Explanation.  To resolve problems due to simultaneous use of two nearly identical versions of the foot, collaborative action is being taken by the National Institute of Standards and Technology (NIST) the National Geodetic Survey (NGS), the National Ocean Service (NOS), and the National Oceanic and Atmospheric Administration (NOAA) to provide national uniformity in the measurement of length. To this end, the “U.S. survey foot” will be phased out as part of the modernization of the National Spatial Reference System (NSRS), and on 12/31/2022 the “international foot” will be used and called the “foot.”

The current NRCS definition of the foot for surveying can be found in the National Engineering Handbook Part 650, Chapter 1- Surveying. Section 650.0103 Units of Measure, A., where 1 foot = 0.3048 meters.
Therefore, the existing NRCS definition of the foot for surveying is in keeping with NIST’s definition and goal of providing national uniformity in the measurement of length, all NRCS work such as planning, mapping, engineering and non-engineering designs including geodetic surveying, 1 foot = 0.3048 meters must be used after 12/31/2022, unless state laws require a different definition.

For further information see:  https://www.nist.gov/pml/us-surveyfoot.
Contact.  For questions about this bulletin, contact Arthur Ramthun, P.E., National Construction Engineer, at (202) 906-0010 or Arthur.ramthun@usda.gov.   


 Deputy Chief for Science and Technology

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