Ground to Grid Question

eight miles or 0.8 miles? if there are no specifications on the project, why not state that the survey is published in ground coordinates?

my guess is it would also depend on the nature of the project and the end result of the survey...

Posted by: @muncle56

I've been asked to convert the entire job to SPC...

I would ask the person/entity requesting this why they want it in SPC and what they intend to do with it. Once most of my clients are properly educated, they often drop this requirement.

Yep, your plan is good.?ÿ Don't overcomplicate it.?ÿ There are lots of good reasons to have a job in SPC.

Sorry, I know similar questions to this have been asked on this forum

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Iƒ??m sure similar questions are on the licensing exam too. And Iƒ??d suspect reference books are in your office.?ÿ

and always publish your metadata so others can convert from grid to ground and back, et cetera

The procedure you proposed would work, but I would be uncomfortable with RTK Control. If you have additional receivers, static the endpoints while simultaneously occupying various horizontal and vertical control in the area. You can verify the middle points with RTK. Then you can certify an accuracy beyond your required without a lot of work. If you only have one receiver, OPUS four points, it will take you all day, but any mistakes will show up.?ÿ Good Luck.?ÿ

Project is 0.8 miles long and 0.2 miles at it's widest.?ÿ Results will be given to a consultant who will then pass it off to their surveyor who will then do additional topo and location work (no boundary work as far as I know.) This will all then be given to the consultants design team.?ÿ Site is a park like setting which is being updated.

For now I think they just want to overlay aerials with the ground work, but eventually there will be layout involved.

I think I would apply the ground-to-grid scale factor on the traverse legs only, easy to do.?ÿ If elevations are important, run differential levels between the control points.?ÿ Do a graphical rotation of your open traverse control points in Civil3D between your GPS observations.?ÿ Then back to business as usual, occupying your control points for RTK and total station work.?ÿ

Keep it simple, don't over-complicate it if you don't have the experience and back ground. Stay within your comfort level and you will sleep better at night knowing that it's right.?ÿ Level loops don't lie, and a couple tenths horizontally doesn't hurt anything unless you are construction staking.?ÿ ?ÿ?ÿ

Call up a few local surveyors, who work regularly in SPC. A short consultation with them, maybe repeated, to check your work is really in order here.

You can figure out alot, but a double check will help here.

N

I'm in NY and can help. If the nearest RTN base is farther than 5 miles then NYSNET may not be sufficient to get you on SPC, as the error ellipses may likely introduce a false scale factor. It also depends how far you from the center of the state plane zone. I suggest you locate coordinate pairs at each end of the traverse, preferably with four simultaneously running recievers for an hour. I have eight GNSS just for this purpose. Then post process the static wirh the EDM using LeastSquares. Are you in NY east or NY Long Island zone?

In many states applying SPC to a project falls within the bounds of professional land surveying.?ÿ If you are being asked to do so and are not licensed, you are setting yourself up for trouble.?ÿ If you are licensed and are struggling with this process you need to put the rover away for a bit and get yourself spun up on basic geodesy principles, GNSS basics, reference frames, and coordinate transformations.?ÿ But rest assured probably 80% of daily GNSS users have know idea what is really going on under the hood.?ÿ

Your probelm is a basic geodetic control procedure.?ÿ There are a lot of manuals out there that provide step by step best practices.?ÿ A word of advice...be very careful translating and rotating in C3D.?ÿ There are 4 principles to a reference frame: orgin, X,Y,Z, Scale, and Reference Point.

It should work to do what you're wanting to do.

With such a small job tying in the beginning and ending points, then doing an align will "get you close".

Some checks in the middle and you'll be golden, it's not that complicated really. If you get SPC on two points and rotate/scale down it's how many jobs have been converted to SPC control for many years. Not the perfect for sure, but it's not worth resurveying it.?ÿ

You don't have to get into the weeds of the computation that create SPC, that was the entire point of the system and why it was set-up the way is was,,,,,,,,wwwwaaaaayyyyyy before GPS existed. It's intended to be used as a simple system for surveyors to be on a Geodetic system without all the difficult work involved in running a geodetic survey, it's done for you. Frankly, today it's button pushing, not like it was in the old SPC days and even then most didn't get into geodetic computations, they surveyed conventionally and reduced distances using a chart in a SPC book to get grid scales and divided the radius of the earth (20,906,000') by the radius plus the elevation. That's all there was to it. Very few surveyors ever translated from LAT, LONG to SPC or from SPC to LAT, LONG.?ÿ

Be sure to use the correct scale factor. Not always scale down from ground to grid. I live a mile from the edge of SPC zones and it would be scale up from ground to grid. In some areas down the CSF may equate 1:10000, if in high elevation it could be even worse.?ÿ

Itƒ??s 2022, this is a barely an SIT question.?ÿ

Posted by: @larry-scott

Itƒ??s 2022, this is a barely an SIT question.?ÿ

There was a time before you knew everything too...

@michigan-left?ÿ
he working fee for service with RTK.?ÿ

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For 0.8 miles I would think 5 to 10 geodetic points would be way overkill.?ÿ Three (3), two for translation rotation and scale with a third as a check.?ÿ Best practice would be to reduce and adjust the conventional control network on the grid.?ÿ Most of the major survey based software will allow you to enter scale factors for processing on grid.?ÿ Once you have a good grid based adjustment then you can bring it down to ground.

Posted by: @leegreen

Be sure to use the correct scale factor. Not always scale down from ground to grid. I live a mile from the edge of SPC zones and it would be scale up from ground to grid. In some areas down the CSF may equate 1:10000, if in high elevation it could be even worse.?ÿ

I think you mean if in low elevation it might get larger than 1. ????

There are a lot of possible reasons to place a project on state plane, and the phrase "on state plane" can mean very different things depending on those reasons. It also only encompasses the horizontal datum; vertical is another matter entirely.

Sometimes a simple translate/rotate is good enough. Sometimes a scale factor is needed. Other times the situation necessitates a full-blown network adjustment, or least squares/Helmert transformation of coordinates.

I second the suggestion of @stlsurveyor to do some reading up on geodesy, GNSS, transformations, etc. Knowledge of those topics should be second nature for any licensed land surveyor or geospatial professional.

No matter what you do, document it thoroughly as you have discussed. I would suggest placing a disclaimer stating what the original specifications and intent of the project were, that your data are not intended to be used for any other purpose, and if they are going to be used for another purpose it is the responsibility of the end user to validate the data and take on any liability.

A lot of folks think that survey control is absolute and/or perfect. A little metadata [CYA] up front will go a long way towards helping you out if someone down the line tries to use your data for something it shouldn't be used for.