Your post reminded me of my interest in the international foot vs. U.S. survey foot circa 1998. Below are two emails.
The first one submitted by me. The second one submitted by the respondent. I have omitted the name and company
of the respondent out of respect for their privacy.
I read your question at SMI's site concerning the international foot. I do work for Universal Studios down here in Orlando, FL.
The plans for the flume ride come from Holland, and the coordinates are in both millimeters and feet and decimal inches.
The units menu of the HP 48GX uses the international foot for unit conversions. Davis and Foote state that unless you're
using 6 or more figures after the decimal point, the difference between the U.S. survey foot and the international foot is
very small. I would like to discuss this subject further with you.
Thanks for the reply. Prior to receiving your email, we had talked with Mr. Trent and he assured us that we need not worry
about the difference between U.S. and int'l foot. The problem we were having was that we had GPS control points (state
plane coordinates) set at the beginning, middle and end of a route survey, and when we ran from (1) point to the next
applying our scale factor we were having a problem checking into the next known coordinate from 0.13' to 0.36'. We
weren't too upset about the 0.13' because we had traversed roughly 2,500' with several breaks in our traverse, however,
when we used an older version of the Sokkia SDR-33 we checked a lot tighter. One theory we have is that our GPS coordinates
that were provided to us by another surveyor already had some error built in therefore causing problems from the get go.
When we originally purchased the SMI software nobody ever made any mention of the fact that it was reading in an int'l foot and
when I called their technical support people the guy told me that they had an up-date that would read full time in U.S. foot.
Upon hearing this, I immediately felt that this might be some of the reason my points were not checking in with one another.
However, Mr. Trent (as I said earlier) assured us that this was not the problem therefore we were left with egg on our face
trying to figure out how to get this thing to work.
How about a list of "special" states that use IFT for Horizontal and USFT for elevation....
[sarcasm]Montana- A special place....[/sarcasm]
Field Dog, post: 363241, member: 9186 wrote: Prior to receiving your email, we had talked with Mr. Trent and he assured us that we need not worry about the difference between U.S. and int'l foot.
This is one example where experience trumps expert education. As long as you're dealing only with distances, Mr. Trent was correct. But you were dealing with very large coordinate values and you saw a problem firsthand. When you inversed a pair of bad coordinates, the problem likely went away. That is, the distances were unaffected.
The Table 1 from the POB article is not entirely up to date. Before retiring from NGS I was the keeper of all things dealing with State Plane Coordinates. Vermont uses the U.S. Foot as defined in their state statute while the states of Maine, Nebraska, Utah, and West Virginia all adopted the U.S. Survey Foot as their official conversion from meters by publishing the change as a notice in the Federal Register.
base9geodesy, post: 363263, member: 7189 wrote: ... by publishing the change as a notice in the Federal Register.
Does a West Virginia surveyor need to be aware of the date of that change?
August 17, 2007 -- http://www.ngs.noaa.gov/PUBS_LIB/PublicationofNorthAmericanDatumof1983StatePlaneCoordinatesinFeetinWestVirginia.pdf
I love the way you guys call it the "international" foot when its only the US that uses it 🙂
jim.cox, post: 363271, member: 93 wrote: I love the way you guys call it the "international" foot when its only the US that uses it 🙂
After the misery of the metric wars of the 80's, I'm good with either foot, but I prefer the US one, can't understand Montana's reasons, they should just use the us one like everyone else.:-S
The use of the term "international" for the foot is derived from the 1959 Federal Register Notice by the Bureau of Standards (now the National Institute of Standards and Technology - NIST) which describes the new relationship between the yard and the meter and defines the new yard as the "International Yard" and hence the foot becomes the "International Foot" -- http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf
base9geodesy, post: 363284, member: 7189 wrote: The use of the term "international" for the foot is derived from the 1959 Federal Register Notice by the Bureau of Standards (now the National Institute of Standards and Technology - NIST) which describes the new relationship between the yard and the meter and defines the new yard as the "International Yard" and hence the foot becomes the "International Foot" -- http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf
I might add that it was based on an international agreement in 1959 to define the foot, which supposedly overroad the previous foot definition of 39.37" = 1 meter. NAD'27 feet were, obviously based on the older definition. Since it is most detrimental in the case of State Plane Coordinates, it was already defined in North American Datum.
jim.cox, post: 363271, member: 93 wrote: I love the way you guys call it the "international" foot when its only the US that uses it 🙂
When I worked in Canada it was frequently necessary to convert new building plans and old survey records in feet to metres, and we always used the international foot definition to do it. We didn't know there was any other option.
Personally, I do not understand the reason for anyone hanging on to the old foot defined at 39.37/1200. American industry in 1933 decided the exact conversion 1 inch = 2.54 centimeters was what they'd use. Why, why do surveyors in the year 2016 hang on to a nearly 100-year old conversion. It is long past time to switch to meters!
http://www.pobonline.com/articles/91503-letters-december-2007
Personally I don't care so long as whichever one is in use is clearly and unambiguously specified. My own preference is for meters.
I suspect the International foot was created as part of an attempt to promote the metric system by confounding us with dueling foot units.
Accuracy was certainly not a motivation.
JAC
see also the NGS video http://www.ngs.noaa.gov/corbin/class_description/NGS_Video_Library.shtml&apos ;">Two 'Right' Feet? Understanding the Difference Between U.S. Survey Feet and International Feet (2:39)
The list is correct with respect to SC, International Foot.
astrodanco, post: 363336, member: 7558 wrote: Personally I don't care so long as whichever one is in use is clearly and unambiguously specified. My own preference is for meters.
Meters aren't going to be all that helpful for the property owner who needs to figure out how the new proposed zoning ordinance, with property line offsets, is going to affect him, or be very helpful for the property tax listers who need to enter the area of the lot in acres.
Feet is such a superior unit for measurement, it would be a shame to discontinue using it:-(
spledeus, post: 363167, member: 3579 wrote: My first run in was in RI. 3 firms performing layout work and one used I.Ft. We were the last and the building did not match the driveway by 1.1 feet. Nice and small RI...
What is the biggest difference in SPCS conversion from meters? I get about seven feet here.
Either Nevada East (false northing) or Michigan North (false easting) with 8 million. Nevada East wins out as the northern border is around 28.9 million feet (either one). Let's call it 8.8 million meters.
8800000 / 0.3048 = 28871391.076 iFt
8800000 * 3.28083333333333 = 28871333.333 USFt
57.743 "feet"