US Survey Foot - State Plane Coordinates

Changing to IF doesn't make sense to me in the situation you're describing. Not unless California is codifying the change.?ÿ

A letter from the NGS SPC2022 Project Manager (Scott posted this on the CLSA board):

Hi Scott,

You are correct, NGS (and NIST) are?ÿNOT?ÿtelling states that use the U.S. survey foot (sft) for SPCS 83 (or SPCS 27) to start using the international foot (ift) at this time, despite deprecation of the sft on 12/31/2022.
States currently using the sft for SPCS 83 should continue to do so. The ift will be used for all zones in every state for SPCS2022 (and every other component of the National Spatial Reference System), but that wonƒ??t be implemented until 2025.
The reason for continuing to use the sft for SPCS 83 is that it is an existing ƒ??legacyƒ? system, and it would cause too much disruption to change the foot definition. NGS will always support the sft for SPCS 83 in states that have officially adopted the sft for SPCS 83, even after SPCS2022 has been implemented. The same is true for SPCS 27 in all states.
More information and resources about this topic that you may find helpful are given below. Since this is a recurring topic of confusion, please feel free to share this information far and wide!
ƒ?› You may have already seen the ƒ??final determinationƒ? Federal Register Notice (FRN) on deprecation of the sft issued on 10/5/2020 ( https://www.federalregister.gov/documen ... urvey-foot). But if you have not read it closely and in its entirety, I encourage you to do so. It contains a lot of information that may answer your questions. The FRN includes information on the continued use of sft for legacy applications (such as SPCS 83). That is stated in the last paragraph of the ƒ??Notice of Final Determinationƒ? section; in items #1 and #2 in the ƒ??Counterpoints to Feedback Expressing Oppositionƒ? section; and in the second paragraph of the ƒ??Implementation Summary and Actionsƒ? section.
ƒ?› The legacy issue is also addressed in the 10th FAQ on the NIST website ( https://www.nist.gov/pml/us-surveyfoot/ ... tions-faqs) and in the 11th FAQ on our ƒ??new datumsƒ? FAQs web page ( https://geodesy.noaa.gov/datums/newdatu ... tums.shtml).
ƒ?› The 40 states that officially adopted the sft for SPCS 83 are listed in Table C.1 of Appendix C of NOAA Special Publication NOS NGS 13, ƒ??The State Plane Coordinate System History, Policy, and Future Directionsƒ? ( https://geodesy.noaa.gov/library/pdfs/SP_NOS_NGS_13.pdf ).
ƒ?› Information on NSRS legislation that includes foot definitions is available under item #5 on the new datums ƒ??Get Preparedƒ? web page ( https://geodesy.noaa.gov/datums/newdatu ... ared.shtml). There is a legislation template ( https://cdn.ymaws.com/www.nsps.us.com/r ... -Templ.pdf), as well as actual new legislation from several states that can serve as examples ( https://geodesy.noaa.gov/pub/SPCS/ExampleLegislation/ ).
ƒ?› The final determination FRN is itself not actually a law, although Congress has passed several laws giving the National Institute of Standards and Technology (NIST) the authority to maintain national standards of measurement. These and other related federal laws are given in the initial sft FRN issued on 10/17/2019 ( https://www.federalregister.gov/documen ... urvey-foot).
People will continue to use SPCS 83 at least until SPCS2022 is rolled out in 2025. Those states using the sft for SPCS 83 should continue to do so. That means they should continue to use the sft in their equipment and associated software (such as GIS and CAD). Situations may occur after 2022 where an organization uses custom (non-SPCS) coordinate systems. In such cases, my recommendation is to use the sft if it is also being used for SPCS 83. Trying to manage a partial switch (where some things use the ift and others use the sft at the same time) could cause confusion and lead to mistakes. This is in keeping with the ƒ??orderly transitionƒ? idea stated in the final determination FRN. We understand that the transition may take some time for certain organizations, and thatƒ??s OK. The most important part is that it occurs in an orderly fashion. Over time use of the sft will diminish, and we expect that to accelerate after SPCS2022 is released in 2025.
On Nov 10, I also be gave a webinar on deprecation of the sft and the status of SPCS2022 ( https://geodesy.noaa.gov/web/science_ed ... 2022.shtml).

@jim-frame?ÿ

Thanks.?ÿ This makes sense.?ÿ ?ÿI am in NY/NJ and it is similar.

I'm not a surveyor, but now and then I look at fairly recent surveys as a Vermont justice of the peace. The ones I've seen for single residential lots do not have any state plane or latitude/longitude information on them. As best as I can recall, they mentioned feet but didn't distinguish between survey feet or international feet. Of course, the equipment that was used probably couldn't distinguish the two in that situation.

Suppose one were converting such a survey, dated January 4, 2023, to SI units. Just as a matter of being formally correct, would one use the international foot conversion factor because the drawing does not involve SPCS and except for legacy applications, the survey foot should not be used, according to the federal government, which has the constitutional authority to set the standards for weights and measures? Or should one use the survey foot conversion factor since Vermont uses the survey foot for SPSS (and just ignore that the survey doesn't involve SPSS)?

An alternative is to just do whatever you want and in some appropriate place write a statement that it doesn't matter because the difference is undetectable.

A related issue is if a survey firm has a standard layout for drawings that contains a statement that survey feet are used, should it be changed for non-SPSS drawings to either say international feet, or just feet?

The difference between the US SF and International foot is about 0.01' in a mile. Immaterial for most boundary surveys in urban areas. This change has nothing to do with boundary surveying, despite some of the claims that were made during the FRN public comment period.

@spmpls You are correct unless using a SPC zone that have false easting or false northing values in the hundreds of thousands or millions. Then the difference between the international foot and US survey foot does make a difference.

Melita,

Absolutely that is where the difference is magnified enough to make a significant difference. I was trying to address the comments from ashton regarding the reporting of feet on Vermont residential lot surveys.

Scott

I suspect that for most firms, there will be far more internal problems than external problems.

Whether a project is conducted for topography, right-of-way, control, boundary, construction, etc., the vast majority of US practitioners tie their work to a geodetic datum and work in a projected coordinate system?ÿ where computations are performed in meters, but displayed in feet.

I don't see many surveyors who operate in a total coordinate-free world.

The software cares, even if the practitioner does not.

And it begins. ?ÿThis will keep a lot of us in business because one could using international feet and other us sft. ?ÿWhat a cluster this can cause. I saw this from larger multi state firms during my time doing support. Company come from South Carolina international foot to work in Georgia us sft ring ring i am missing the monument by x feet in x county. Ok ck your units. They are feet. Which foot. The one I always use in South Carolina. Ok so change units to usft ok how does it check. ?ÿGreeaaat just like frosted flakes and tony the tiger sais. ?ÿI have to agree above that NGS has repeatedly stated you should continue on usft on nad83 if that is what you are using. ?ÿMake the switch with new datum.?ÿ

And it begins. ?ÿThis will keep a lot of us in business because one could using international feet and other us sft. ?ÿWhat a cluster this can cause. I saw this from larger multi state firms during my time doing support. Company come from South Carolina international foot to work in Georgia us sft ring ring i am missing the monument by x feet in x county. Ok ck your units. They are feet. Which foot. The one I always use in South Carolina. Ok so change units to usft ok how does it check. ?ÿGreeaaat just like frosted flakes and tony the tiger sais. ?ÿI have to agree above that NGS has repeatedly stated you should continue on usft on nad83 if that is what you are using. ?ÿMake the switch with new datum.?ÿ

Ift and USft mix up is something to watch out for. I've seen it both ways, international feet applied in a state using USft and USft applied in a state defined as international.?ÿ

Always be on the lookout for it, the new data should make the change simple: all states in international foot.?ÿ

The difference is about 2ppm, if you're surveying boundaries more accurately than that; I tip my hat to ya!

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Here is something I suggest. ?ÿI have been on this both ways and i will personally build a small spreadsheet randomly taking coordinates from each county and converting both ways from meters to usft and international foot. And when new datum comes out i will do it again. Why. It will keep Murphy away. ?ÿAnd when i am called by one of my crew chiefs and he sais i am not hitting x companies control i can simply look and say you are x feet off ok well i will call the surveyor because he used his left foot instead of the right foot no big deal. ????. I did this in previous states and kept a ellipse to ortho heights sheet and navd88 to ngvd29 and nad27 to nad83 i have seen all of these intertwined. I still have 3.28083333333333333 in my brain how will i ever get it out and use only .3048. It does not compute ?????ÿ

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Guess thatƒ??s something else to watch out for. ???? If I recall, Trimble DCƒ??s would allow you to select units when you create a job regardless of projection used. Iƒ??d assume other brands allow this as well? Iƒ??ll have to check to see if Topcon will. ?????ÿ

If I recall, Trimble DCƒ??s would allow you to select units when you create a job regardless of projection used. Iƒ??d assume other brands allow this as well?

I guess there could be some exceptions, but in my experience most software packages work and compute everything in meters under the hood, so it's easy to incorporate alternate units by using a conversion factor at the time of display or user input.