It is well known that the USA uses miles, feet and inches and they are identical to the English versions of these units used in the UK. What is a lot less well known is the fact that the USA had two official feet, the international foot and the survey foot. By extension, there were also two versions of derived units based on these two feet. So there were survey and international versions of common units such as the mile, yard and inch. The US survey foot was deprecated at the end of last year. This deprecation act shows the importance of ensuring uniformity and common standards in measurement matters.
The USA decided to replace the customary standards of length based on those of England with length definitions based on metric units. The survey foot was introduced by the Mendenhall Order of 1893 when it was fixed as exactly 1200/3937 metres. When expressed as a decimal, a survey foot is approximately 0.3048006096 metres.
The international foot was introduced by agreement between several English-speaking countries, including the UK and USA, in 1959 to standardise the English foot worldwide at exactly 0.3048 metres. This eliminated the tiny differences in foot definitions between these countries. This was important for applications such as precision engineering, mutual compatibility of spare parts and interoperability of weapons systems between armed forces.
After 1959, the USA continued to use the survey foot for geodetic surveying but used the international foot for everything else. Thus the USA has had two official feet for over 60 years. Despite the fact that the difference between the two was less than 0.7 micrometres in length, it can lead to confusion and costly errors and delays for various types of projects. The elimination of the survey foot will reduce surveying errors that can cost money. For distances of hundreds or thousands of miles between co-ordinates, the difference between the survey foot and the international foot can add up to several feet.
For these reasons, the National Oceanic and Atmospheric Administration (NOAA), the National Ocean Service (NOS), the National Geodetic Survey (NGS) and the National Institute of Standards and Technology (NIST) decided to retire the survey foot at the end of last year and just use the international foot instead from 1 January 2023 onwards. The goal of deprecating the survey foot is to provide national uniformity of length measurements and resolve the problems with the simultaneous use of two versions of the foot with slightly different lengths. This is part of the modernisation of the National Spatial Reference System (NSRS).
In the Summary section of the Federal Register Notice (FRN) published by NIST and NOAA, it states:
“This notice announces the final decision to deprecate use of the “U.S. survey foot” on December 31, 2022. Beginning on January 1, 2023, the U.S. survey foot should not be used and will be superseded by the “international foot” definition (i.e., 1 foot = 0.3048 meter exactly) in all applications. The international foot is currently used throughout the U.S. for a large majority of applications and is typically referred to as simply the “foot.” Over time this terminology will become more prevalent in land surveying and mapping communities. Either the term “foot” or “international foot” may be used, as required for clarity in technical applications.”
In a nutshell, 31 December 2022 was the last day the US survey foot should be used and from 1 January 2023, the US survey foot is deemed obsolete and superseded by the international foot (also known as the foot) equal to 0.3048 metres exactly for all applications.
The standardisation of the foot measurement and its derivatives across the USA shows the importance of enforcing uniformity and common standards of measurement. The action taken by US federal agencies to eliminate survey measures should hold an important lesson for the British Government. This is a lesson the Government does not want to learn. It seems that the Government wants to go in the opposite direction by increasing the number of authorised units for trade and commerce.
10 thoughts on “Retirement of the US survey foot”
A couple of minor corrections:
First there is no Survey inch (and I am not sure about the yard) Surveyors use decimal feet, not feet and inches. However, all historic surveying terms, links, rods, chains, furlongs, as well miles and acres had two definitions. NGS does all their geodetic work in meters, but the states balked at metrication. The resolution was that NGS agreed to multiple these values by 3937/1200 or 1250/381, if the state defined in law which foot it intended to use. (8 states used the international foot, the rest, the survey foot.
Second. the difference is mainly an issue in State Plane Coordinate Systems (SPSC), and release of new SPCS2022 is actually delayed until 2025. NGS has committed to supporting the Survey foot in legacy products for states that have been using the survey foot.
NIST is deprecating it and changing how to refer to which foot is in use (the survey foot only for legacy applications). I have joked it is not dead yet, but is in hospice care.
If you have 17 minutes of your life to spare, you can watch this video to learn how to convert from inches and fractions of inches, and feet and inches and fractions of inches to decimal inches or decimal feet, and how to check your calculations using three different types of imperial tape measure:
“How to Convert Feet & Inches into Feet and Decimal Feet”
Or, you could simply do all your measurements and work using the decimal metric system.
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I wish the USA would finally deprecate all the old measures (not just the survey foot) and finally switch to SI.
Right now I am watching a science fiction show on Netflix called “Away” about the first crewed mission to Mars. The crew is international with only one American crew member, so all the other members come from countries that use metric.
This is about a futuristic NASA program, so I would expect all the units used to be metric.
But no! Only Imperial (or USA equivalent) is used throughout. Nothing in the show but “feet” “inches” “pounds” and the dreaded use of degrees Fahrenheit but without even mentioning that it is actually Fahrenheit, just stuff like “his temperature is 98.6”. Huh? 98.6 what, for heaven’s sake!
After all those episodes on TV of Star Trek over decades where only metric was used, you would think such a space program set in the future would be written to use metric as well these days.
I cannot being to tell you how disheartening this is and how disappointed I am in the producers of that show. Gene Rodenberry must be rolling over in his grave. 😦
@Ezra Steinberg 2023-02-25
Maybe we can take comfort from the fact that Star Trek ran for many years and is still running.
“Away” was apparently cancelled after the first season with rather poor ratings.
Personally I have never heard of it before now, never want to hear of it again. I cannot see how it could gain traction in any country outside of USA, not even UK given the expected audience base.
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Netflix is currently receiving a lot of bad press in the UK, incuding comments by the Queen Consort. Netflix’s crime? They acquired the copyright of Roald Dahl from the Dahl estate (https://en.wikipedia.org/wiki/Roald_Dahl) and are now “sanitising” his writings. Rather typical of Dahl’s writings was to retell the story of Little Red Riding Hood in a way that would appeal to ten-year-olds. In Dahl’s version, Red Riding Hood pulled a pistol from her knickers (“panties” in US English). (See https://en.wikipedia.org/wiki/Revolting_Rhymes)
An example of the changes being made by Netflix cocerns a characters in one of his books was Augustine Gloop, a very greedy child, who Dahl described as being “fat”. Netflix now describe him as being “enormous”. Many similar changes have been made.
@Ezra Steinberg this gets more frustrating if you watch manned launches on NASA TV at the moment. If it’s a SpaceX launch all the on-screen displays are metric, If it’s a ULA/Boeing launch they’re all USC. Either way the official NASA commentary almost always uses USC except for a few instances (but usually only while the commentator is trying to convert for the viewers).
As it happens, the last few episodes of the “Away” program switched to using metric!
Makes me wonder if the writers and producers got feedback from fans (including many “Star Trek” fans, I’ll wager) who said it was a crying shame to cater only to a fairly middle of the road American audience after so many sci-fi tv shows and movies have been produced over the decades where metric was used exclusively. To me it was very jarring for such an otherwise fine show that actually tried to highlight the need for universal cooperation and harmony to spoil things by having the actors use Imperial.
Sadly, the show got canceled after just one season once the crew landed on Mars.
Also sad is the latest polling in the USA showing only a minority of those asked actually approve of converting the USA to metric. Not sure what it will take to get this country out of its rut and join the rest of the world.
It can reasonably be concluded that it is the US that is the drag anchor on the UK’s completion of its metric changeover. I remember asking an ardent imperialist years ago what he would do if the US announced they were metricating their road signs. I suggested he would be among the first clamouring for the UK to change their signs to be like the US. Talk about 51st state!
So true about the USA being dead weight when it comes to converting to metric. What a shame.
In terms of the final Imperial hold outs like the USA someone on the USMA mailing list sent out some news indicating that both Liberia (because of the influence of the Economic Community of West African States) and Myanmar (Burma) are making great strides in using more and more metric instead of Imperial (or instead of the local traditional set of measurement units).
So it seems that that old chestnut about how the lone Imperial holdouts on the planet are the USA, Myanmar, and Liberia is not really true any more — it’s mostly just the USA now especially given its outsize global influence in entertainment, media, economics, etc.
(There are also stories about Belize using Imperial in. some areas of commerce and the media that make me wonder what’s really going on there. Maybe someone on this site has some info they can dig up or know about and can share.)
@Ezra: I don’t know how things work in the United States, but in the United Kingdom one can (in theory) write to one’s member of parliament and question why certain published information is out of date. Would it help if somebody from the USMA were to write to their member of congress asking how frequently the CIA cross-check the information that they publish in “The World Fact Book” particularly the information contained in Appendix G In particular one should look at:
1. the opening sentence is probably out of date, depending how the phrase “have not adopted the International System of Units (SI, or metric system) as their official system of weights and measures” in interpreted.
2. The Appendix has not yet been updated in respect of the metric prefixes “quetta”, “ronna”, “ronto” and “quecto”. These metric prefixes can be found at https://www.nist.gov/pml/owm/metric-si-prefixes.