US Survey Foot and Low Distortion Projections

[avoidthelloyd]

Some of you have already experienced what is coming to Oklahoma. New low distortion projections and the discontinuation of the US survey foot.

What are your experiences and thoughts on how to handle your old data? Let’s face it, a lot of you are high mileage and you have floppy disks in that drawer there next to you that still work on that computer with the monochrome monitor in the corner. Haha.

How have you adapted to new conditions? Is the LS setup and ready for this? Are the settings available? Do you do anything manually?

I appreciate any thoughts. Thanks!

 

[Shawn Billings]

That's a great question and has a lot of nuance. The short answer is that I don't believe any manufacturer is ready for the new 2022 reference frames or the new projections that will accompany them. Mostly this is because the transformation software doesn't exist yet and the projections have not been formally released by NGS yet, so there really isn't anything a manufacturer can release at this time in preparation for 2022.

For now, surveyors should spend some time reading the blueprint documents from NGS: https://geodesy.noaa.gov/datums/newdatums/policy.shtml

Second, surveyors should begin improving their metadata today. If your surveys don't presently attribute the distance units, you should begin now. The difference between US Survey Feet and International Feet is 2ppm. No one will see 2ppm in distances shown on most surveys. You won't see 2ppm in an EDM measurement unless you're doing industrial metrology. But 2ppm gets significant when reporting coordinates valued in the millions. A coordinate of 1,000,000 will differ by 2 at 2ppm.

As was pointed out in the North Carolina unit discussion, surveyors in States with the US Survey Foot should continue using the US Survey Foot with State Plane 1983 coordinates, and switch to International Foot when using 2022.

I'll try to share more details on what 2022 will bring and what surveyors need to prepare for as time allows. Great questions.

 

[avoidthelloyd]

" surveyors should begin improving their metadata today. If your surveys don't presently attribute the distance units, you should begin now. "

Thanks. Please elaborate. What does 'attribute the distance units' mean?

 

[Shawn Billings]

What does 'attribute the distance units' mean?

That was poorly worded on my part. I mean that surveyors should put on their maps and reports that the distances are expressed in US Survey Feet, or in International Feet. The unit has probably always seemed axiomatic, but now we see that in the future the units are not a given.