ESRI 102733 correct units

Units should be “ift” international foot
1’ = 0.3048 meters exactly

This is legal unit of measurement in the State of South Carolina

Hi, @EBE111057
It looks like ESRI:102733 indeed has US survey foot unit of measure. You can make sure of this here.

But there are also available another coordinate system with required parameters. Please, check out EPSG:2273(NAD83 / South Carolina (ft)) maybe that’s the coordinate system you’re looking for.

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ESRI is wrong. This and other projection parameters issued by them have been a source of contention with surveyors and software developers for years. Apparently they don’t know how to either comprehend or read and refuse to change parameters published by them when shown correct data


Pages from NOAA_Manual_NOS_NGS_0005 page9.pdf (146.8 KB)

ESRI is not the know all in geodetic datums and projections

Thanks for providing another projection. Even this one should be labeled “ift” instead of “ft”

I think for South Carolina you should be using one of these. The U.S. State Plane system does not use IFT so it is either M (no label) or FT (USFT).

image

There might be instances of where HARN is used so be aware of that. I have a couple of people that I have been working with that have hit HARN on projects that absolutely should not have been using it.

All our projects are based on NAD83(2011) coordinates EPOCH: 2010, NGS’s current realization. Most of the latest adjusted passive stations and ALL CORS are referenced to this datum. HARN stations are on a different datum and were the product of early GPS use. Some have been adjusted to the current datum, others not. Knowledge of the different datums and projections used by NGS is often not known to the common land surveyor who is still surveying in the 80’s.

The SPCS83 manual and NGS data sheets specifically states the difference between meters, usft and ift units.

I live and work in SC and have been a licensed registered land surveyor since 1985. As stated earlier and in the SPCS83 manual, the international foot “ift” is the legal unit of measurement in SC. I use it everyday

Thanks for the clarification and credentials. As I stated I work with a few people in SC that have different use-cases and I work in Texas so our use is even further off. I now understand the reference to international feet, but that EPSG is from 2007 correct? Does it us a specific transformation that you have to use? Otherwise it is not 2011 and is outdated. State law defines system in International feet, not USFT. Federal definition is metric - see CRS code 32133. For applications with an accuracy of better than 3 feet, replaced by NAD83(HARN) / SPCS.

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Since this has turned into a rather big discussion, I’ve decided to make it a separate thread. Thanks for the tip, @EBE111057. Right now it’s easier for us to build coordinate system support around the registries, but we understand that sometimes they may not accurately represent the actual state of things.

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I hadn’t seen those Michael. I’ll review and see how they compare. If there’s a question on parameters, I usually refer back to the SPCS83 doc. One good thing about the new 2022 datum for the US, it’ll all be “ift” in the CONUS

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I can’t wait for it! :star_struck:

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South Carolina Statute Title 27 Chapter 2 Section 27-2-50 and Appendix C in NOAA Special Publication NOS NGS 13 both identify the international foot as official unit of measure for (NAD83) SP SC. Interestingly, I’ve never seen the “ift” designation before (but it makes sense); instead, just “ft” for the international foot and either “sFT” or “USft” for the survey foot.

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Yep, exactly. Look at a typical datasheet for the stations and CORS in SC, the sheets show either “meters” or “ift”. I had a surveyor argue about our listed coordinates on a project, he had been using “usft” for ties to passive NGS stations for years. He never could understand why his positions didn’t match until I showed him. Coordinates will differ significantly if mixing units.

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