Effective January 1, 2023, the U.S. survey foot will be obsolete. Engineers, mappers, and surveyors will go by the international foot as the unit of measure in the United States. The Federal notice was issued in 2020 by the National Institute of Standards and Technology and National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA), and Department of Commerce (DOC) with the goal to end confusion and discrepancy in having two sets of unit definitions in use.
A U.S. survey foot is 0.3048006 meter, and the international foot is 0.3048 meter. The difference between the two is 0.0000006. This equates to a difference of 2 parts per million (ppm). When a one-mile (5,280 ft) distance is surveyed, the difference is approximately 0.01 ft or 0.12 in.
All projects should use international foot going forward. Partner’s land surveys will use only the international foot as survey units. The difference in length is so slight that it will not be noticeable in most property surveys. Since most surveys are retracement of descriptions in U.S. survey feet, there will be an insignificant effect unless the property is extremely large. However, when we show state plane coordinates, the difference is significant because the coordinate values are in the millions of feet.
The conversion for the State Plane Coordinate System (SPCS), implemented by state jurisdictions, is expected to require a transition period. Expect state plane coordinates to change. Changes in state plane coordinates will accumulate to at least 10,000 meters in all locations. Surveyors should note the unit of measurement utilized on the survey in the surveyors’ notes for clarity. All surveys completed by Partner on or after January 1, 2023, will use only the international foot. Because most surveyors’ calculators allow for an easy switch to international foot, the changes will not trigger delays or cost increases.