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US or INTERNATIONAL FOOT
Posted by spledeus on April 27, 2014 at 8:39 pmWhat does your state use? Are there any countries who use feet other than US? If so, would they use the INTERNATIONAL FOOT or is there another foot out there?
Massachusetts: US SURVEY FOOT.
I have been trying to help an engineer with a project he has. He subcontracted me to provide 3 control points. He has now been wrestling between Meters and Feet with some GIS data. He provided a CAD file and he used International Feet to convert his GIS data.
I double checked my stuff and figured I would share it here.
US SURVEY FOOT
39.37″ = 1 meter (I typically punch 3937/1200 into the computer or calculator)INTERNATIONAL FOOT
0.3048 meter = 1 foot (I do not use this one)The difference is 1.000002 or 1:500,000. No biggie for the typical survey; big trouble then the difference becomes about 6′ in the MA Mainland State Plane. I can only imagine the coordinate shift in a big state…
(Ref: Surveying, Principles and Applications by Barry Kavanagh.)
Unfortunately, Barry states that the US formally adopted the International Foot in 1959. Perhaps the Feds did, but locally we still go state by state.
MA 250 CMR 6.01 (2) Measurements.
(a) Linear measurements shall be expressed in terms of the US Survey Foot or the Meter.
MightyMoe replied 10 years ago 26 Members · 41 Replies- 41 Replies
There are a few states that use the international foot. I know Arizona is one of them. Many countries previously used the foot as the basic measurement of length but all others have officially changed to the meter. All surveys in Canada have been done in meters since 1973 or a little bit after, however feet are still often used in some specific applications (people’s height for example). I know Britain has had quite a bit of hesitation switching to metric, I’m not sure what they use for surveying there.
The following is from the “What & Why” section of http://geodesy.noaa.gov/faq.shtml
>What are the “official” conversions that are used by NGS to convert 1) meters to inches, and 2) meters to feet?
The “official” conversions link includes this:
> Currently, NGS publishes SPCs for 7 states using the U.S. Survey Foot conversion factor, 1 state using the International Foot conversion factor, and 42 states using only meters, not feet, for SPCs. Based on STATE legislation we have or know about, 24 states have legislated the U.S. Survey Foot, 8 states have legislated the International Foot, and 18 states have no legislation on which conversion factor must be used.
Ohio is one of the U.S. Survey Foot states.
> What does your state use?
Oregon uses the Int’l foot with NAD83 and the survey foot with NAD27. Which increasingly means that the Int’l foot is used.Oklahoma and Washington use the US Survey foot.
>Are there any countries who use feet other than US?
I think the the USA is the last holdout.What’s in Your Gun?
S,
Arizona is one of the few that use international feet. At 2ppm, the difference isn’t much, but I’ve wondered how to test which “foot” my Sokkia Set3 shoots. Manual sayeth not. I thought about setting up a really long shot and switching the gun between meters and feet.
Dave
SC does. I run into every so often. Sometimes the surveyor didn’t know and two different people from the same office gave me two different coordinates for the same point. I wish they would pick one and stay with it.
Thad
What’s in Your Gun?
> I thought about setting up a really long shot and switching the gun between meters and feet.
The difference between US Survey Feet and Int’l Feet in a 1 mile EDM shot would be 0.003 feet.MA is a U.S. Survey Foot state. 6 states have legislatively adopted the International Foot for the conversion of State Plane Coordinates – Arizona, Michigan, Montana, North Dakota, Oregon and South Carolina. Utah had done that but later changed to U.S. Survey Feet. With the exceptions of Alabama, Alaska, Hawaii and Missouri which have no specific foot conversion legislated, all the rest of the states have adopted the U.S. Survey foot. The reference source for MA is Massachusetts General Laws, Part 1, Title XV, Chapter 97, Section 8 https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXV/Chapter97/Section8
What’s in Your Gun?
maybe that wants to be 0.003m, or 3 mm. looks like the conversion, in 1 mile, is 0.0106 feet.
or am i converting wrong?
What’s in Your Gun?
I think that you are right. Still, it’s too little to detect which is which by the proposed method.
It’s not much of a difference unless you’re working in state plane. We learned to be careful on a staking job once. Survey Link produces a .job file in IFeet unless you tell it USFeet, and we’d just installed a newer build of Survey Link and didn’t notice. The difference is 6 feet in the eastings. The I-man didn’t know what the warning about mixing different units in the DC meant, so he just clicked okay. Luckily we’d already staked the curb and they had poured it, so the error was immediately apparent. It could have been a costly lesson. Be vigilant.
Time for true confessions . . . I completed my Masters Degree on Map projections in 1980. The foot/meter discussion was on the front burner at NGS at the time and the “official” policy as described in the Federal Register was to use the International Foot for State Plane Systems (if meters were not used). Ultimately, various states objected and “won.” NGS capitulated and subsequently honored choices made by each state with respect to foot units. During that time of transition a number of states adopted their NAD83 laws and (at least two that I know of) based their decision to use the International Foot, at least in part, on my Master’s Thesis.
A better discussion of the U.S. Survey Foot versus using the International Foot is contained in the book I wrote “The 3-D Global Spatial Data Model: Foundation of the Global Spatial Data Infrastructure.” A link to a pertinent portion of Chapter 10 on Map Projections and State Plane Coordinates is posted on my web site.
The shift here amounts to just over 5 feet when working SPC or on any of the GIS systems in the valley. It can bite you in the field, processing or when importing the field book to C3D. My favorite is when someone changes the option in LGO and leaves it… fun times to be sure…
Just another reason to work in metric. It still amazes me the we are the only country in the world that still uses the “English”. Hell, the English don’t even use it anymore.
By the way, that silly little 0.02 feet per mile equals around 15 feet in Oregon North in the Portland area.
Just another reason to work in metric
I used to think that also.
Then I got slapped upside the head doing many projects in metric, if I never, ever, ever see another one I will be happy. I didn’t talk to anyone involved with them that liked it, and they always, always were more expensive because of using metric.
And if we are the only country using the foot, why in the world would we use the international foot??
In CA it has always been the US Survey Foot, unless it was a State job. Then for a few years they tried to conform to metric. Did not work well with the contractors here. Many of them could not grasp the unit conversion. Made many costly ‘mis-stakes’. We often had to write both units on the lath.
Finally the State went back to US Survey foot. Now everyone is all peachy with that.US “Survey” or INTERNATIONAL FOOT
The use of the U.S. Survey Foot by the survey trade is an unforgivable travesty which will burden, haunt and trouble many future surveyors. Continuing to pass this on to future generations should cease. The U.S. Survey Foot should be put to rest.
Tradition’s strangle hold can be tenacious. Twenty-one states of fifty specify US Survey Feet for their state plane coordinate systems. This is despite an industry decision in 1933, 81 years ago, to base the inch as 2.54 centimeters – exact.
http://www.pobonline.com/articles/91503-letters-december-2007
As a matter of attention, it is not the “US Foot” but the “US Survey Foot” when reference is made or intended.
My 12mm (0.04ft) worth!
Metric is the way to go, if working with global clients or simple approach. 1 meter = 100 centimeters = 1000 millimeters. When you walked one short kilometer, you walked 1 million millimeters… always reminds me that $1,000,000 is not a lot of money and could be spent rather quickly….
The one instance where I find the foot more useful is in road works. Stations at 25 ft and 50 ft create a better spacing. 5-10, 20 meters station intervals are okay but using a spacing of 7.62m (25 ft) and 15.24m (50 ft) would be more useful for the equipment operators and overall grade control.
Anyway, look up the story of the “surveyor”, this space craft that crash landed on Mars a few years ago. The reason? Wrong unit by one of the consultants that used miles instead of kilometers for the trajectory calculations… oups:-/
Metric is the way to go, if working with global clients or simple approach. 1 meter = 100 centimeters = 1000 millimeters
Hey, if you think so, then please be my guest. But I’ve had my fill of metric jobs: if the goal is to add pointless costs to a job, then metric IS the way to go, if you want things to run smooth then kick it out the door and never let it back in.
Still hear the groans with a roomful of surveyors and engineers talking to the state over a conference call and hearing that the latest job would be metric (maybe around 10-12 years ago), but then they said; “But this should be the last one”. We all would have cheered if we weren’t so depressed about mucking through ANOTHER metric job. What a pain they were!!!!:-(
And that’s a universal sentiment, never met anyone who beat through a metric job that was happy about it.
And 1 foot = 10 tenths = 100 hundredths; so………..
The U.S. is not the “Lone Ranger” with weird units …
There are numerous countries with weird unit conversions … many of them are prior colonies of the U.K., especially on the African continent. Such variations are due to the various length standards sent to Crown Colonies in the 19th century that were made out of iron or brass “standards.”
Ghana (THE “GOLD COAST”) had a special standards lab constructed just to make comparisons of different “meter bars.”
This has little to zero affect when performing “plane surveys.” It is a “biggie” when performing geodetic calculations because of the magnitude of the parameters involved such as with state plane coordinate transformations.
What’s in Your Gun?
I would wager that all modern total stations measure in meters and the data collector or controller converts to whatever you want to see.
The difference between the two when using state plane coordinates is about 13′ in CA.
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