SPCS 2022 - Get Involved

Shawn, thanks for the detailed information.?ÿ?ÿ

Its still relative to that monument in the ground - isn't it??ÿ Or, is it relative to those SV's overhead?

I can see a rewrite/revision/addition of boundary law in the near future to address issues such as these considering the use of SV's for precise positioning.

No revision of boundary law would be needed.  I don't get why people think a revision of law would be needed.

I don't see any pressing need to change the rules of comparative dignity of calls, but maybe someday. Monuments will always hold (at least for many years) because they are tangible and require no effort on a layperson to recognize them as the boundary. A coordinate still requires the application of special knowledge. Maybe someday a coordinate will supersede a monument when coordinates can be determined with no effort on the part of a layperson. As for bearings and distances... perhaps coordinates should start to weigh in more heavily. Bearings and distances held above area and coordinates because bearings and distances were directly observed while area and coordinates were derived from the raw bearings and distances. But today, for many of us, there are no measured bearings and distances, we're determining coordinates and the bearings and distances are derivatives of the coordinates. But generally, since we're using electronic means to convert between them, there is likely not going to be a discrepancy anyway. 

Now, the definition of the new SPCS zones will need to be codified in State statute. For some States it will be a legislative effort and for others it will be administrative, through some appointed bureaucracy. This has nothing to do with laws related to boundary construction though.

The 2022 SPCS is to be an XYZT system. Using it for boundary control? Hmmm, I'm not feeling that, it's going to be difficult enough for design/build.

I'm not sure how time (velocities) will be handled. I don't know if NGS will periodically pick epochs or if everything will always be current epoch. Either way, I suspect users can select a specific epoch and keep everything relative in their work. It may even be that States can codify a specific epoch as part of the SPCS definitions. Just spit balling.

I do not see the order of dignity of calls to change.

That would be after deed calls are required to be GPS locations.

That will certainly drive lawyers, abstractors and other title mappers up the wall because they can not check the quality of the description or write their own.

0.02

Regarding reference epochs and changing coordinates in 2022, I just found this from a recent paper by NGS:?ÿ

Blueprint for 2022 Part 3: Working in the Modernized NSRS

https://www.ngs.noaa.gov/PUBS_LIB/NOAA_TR_NOS_NGS_0067.pdf

?ÿ

NGS made a commitment to estimate NSRS coordinates at reference epochs (spaced every five years, beginning in 2020.0.) Only by sheer happenstance would a survey take place on January 1, 2020 (or 2025, or 2030, etc.) Therefore, these Reference Epoch coordinates will consist of Final Discrete coordinates and/or Final Running coordinates in combination with the Intra-frame Velocity Model. To execute such a plan requires answers to at least the following questions: 1) When will the coordinates be computed? Before the Reference Epoch? After the Reference Epoch? 2) What data will be used? 3) If, after you have computed the Reference Epoch coordinates, you acquire new data that influences your last Reference Epoch estimate, will you update the coordinates? If so, does that not destroy the entire purpose of those coordinates? 4) What about points with substantially ƒ??oldƒ? data (for example, 20 years or more)? Will NGS continue to estimate Reference Epoch coordinates every five years? Would that not add exponential uncertainty and therefore uselessness of the estimated coordinate? The following plan for Reference Epoch Coordinates is tentative, but it answers the above questions and reflects the current direction we are heading. First, for every Reference Epoch, there will be a unique project: the ƒ??Reference Epoch Computation Project.ƒ? We will compute the vast majority of Reference Epoch Coordinates for the most recently passed reference epoch during the Reference Epoch Computation Project. Each reference epoch computation project will begin two years after the most recently passed reference epoch and will end no more than three years after the most recently passed reference epoch. Example: The ƒ??2020 Reference Epoch Computation Projectƒ? will begin on January 1, 2022 and end no later than December 31, 2022 and produce the vast majority of 2020.0 Reference Epoch Coordinates NGS will provide to the public. It will use data submitted to NGS through December 31, 2021. It will be our policy that, for a given point and a given reference epoch, the Reference Epoch Coordinates will never be changed, with one exception: to correct a blunder. This does not prevent us from adding new points to a Reference Epoch later (especially true considering the massive amount of work to process all historic data in 2022 for the 2020.0 reference epoch). But once computed, a Reference Epoch coordinate will stand in perpetuity. The above details were laid out to make a few things clear: 1) We recognize the strong reliance our NSRS users have on Reference Epoch coordinates in the immediate future,
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2) We recognize frequent changes of Reference Epoch coordinates can cause confusion and job difficulties for NSRS users, 3) We recognize tools, such as NADCON, require definitive Reference Epoch coordinates as input to their creation, and frequently changed Reference Epoch coordinates mean a large pool, rather than a definitive set, will be available. Therefore, the above workflow means marks will never (blunders aside) have more than one set of Reference Epoch coordinates for any given Reference Epoch. From a practical standpoint this means NGS is expecting (and in fact encouraging) a five-year cycle of re-surveying activity at any marks users find particularly useful, in order to keep their Reference Epoch Coordinate uncertainty perpetually small. Without such re-surveys, the Reference Epoch coordinates on points will still be computed, but will gradually become dominated by the propagation of uncertainty in the IFVM throughout the years.

This is a great paper with a lot of information and contains some general overviews of more in-depth papers. The prospects for OPUS are pretty exciting. It also sounds like the passive monuments will be created by us and disseminated by NGS, which is pretty cool.

I believe NGS plans to disseminate their data with the major tectonic plate motion compensated, so to that degree the coordinates of a point will remain nearly fixed at the IGS values they had at some stated epoch, similar to how NAD83 coordinates on a point remain fixed.  IGS marches on, of course, at a few cm/year, so there may be updates after several years to a new epoch.

At the best levels of accuracy there will be small local/regional differences that don't match the overall tectonic plate, due to it not maintaining the same apparent pivot point or warping or whatever, that can be corrected for with additional data.

Bill,

You might find this to be of interest (assuming you haven't already read it).

https://geodesy.noaa.gov/TOOLS/Htdp/Htdp.shtml

Loyal

Thanks @shawn-billings for posting link, very interesting and exciting changes to come at NGS.  Still pondering the GPS month  and processing schedule decisions, and how they would impact project planning.   Sounds like there is flexibility to find their way and some things not set in stone yet. 

Yes. That part seems somewhat prohibitive, but not terribly so.

It appears NGS has decided to perform the plate transformation about the Euhler pole and apply motion functions (local velocities) as well. It also appears that NGS will recalculate points every five years starting with Epoch 2020 sometime in 2022.

Loyal: unfortunately it appears they have abandoned HTDP despite the fact that it is critical for transforming between frames and epochs. I use it all the time for transforming RTX to NAD83 (2011) and also to meet special datum requests from clients. My only real complaint about it (other than it is being discontinued) is that the velocities were "hard-wired" in to the executable rather than being a lookup that could be done to an online maintained file that was regularly updated. So, whenever there was a major earthquake, it required a new version of the program rather than just a new version of a data file. 

I was told recently by someone at NGS that the transformation that Trimble uses to go from ITRF to NAD83 (2011) in the RTX processor does NOT work well in Oregon (and probably other places near the plate boundaries as well) because they are not using HTDP but rather a rigid transformation. 

I will be at the summit next week, hopefully they will announce a replacement for HTDP. 

During my remote presentation at the summit on Monday, I will briefly touch on a dynamic datum modeling tool we have conceptually developed in California. We are working with NGS to pursue the possible next steps for development. Regardless of how much movement over time the NGS is able to model out for the majority of CONUS for NATRF2022, we will still have to manage substantial horizontal velocities that can be quite differential over relatively small areas, tearing epoch date coordinates apart rapidly. Then there are those pesky earthquake things.

you Texas surveyors may not have been required to place state plan coordinates on your plats, but may jurisdictions in Virginia have required same.  Try educating the attorney's team that even though the coordinates are different, it is the same corner - you should be able to tell I am not fond of placing precise dynamic data on a plat and I consider coordinates dynamic no matter how minute the difference may be.

Dignity of calls - I think courts will (some may have already done do) assign a value/dignity to a coordinate.  Current priority works well when monuments and their references are still in.  Does not work so well with coordinates.  Eventually this will all settle out but will take time to do so.  I do think the trend is moving away from a monumented boundary system to a coordinate based system - may not be in this century but it will likely happen - probably when all the surveyors are gone.

I'm OK with it as long as they set 0 degrees longitude through my office, let everyone else move towards or away from me. ???? 

Who says we are moving away from Europe, why can't we say Europe is moving away from us.

The argument against a coordinate being the only know place and value of a clients boundary corner is that it is nothing more than an office survey and that does not satisfy the basic rule that a surveyor has actually been to the property and left footsteps to follow.

By not placing a monument at all corner of the client's property, the surveyor has not met the Texas BOR requirements, the Veterans Land Board and the HUD surveys.

I do not know of a buyer of property that does not want to see the physical location of their monuments and in some instances a marked boundary line defined on the ground.

The middle men such as lawyers, realtors, bankers and title people only want to get the paperwork correct. They usually insist that they are not interested in monuments being set because they do not care and want a surveyor to put their profession in jeopardy.

As I have found, not all states did actually require survey monuments to be set in the past.

In the present that appears to have changed.

In Texas we are required to state that our point of beginning is located in relation to a monument at the record corner of the parent tract of land and to a Headright monument for better reference and give the basis of our bearings in a manner that can be repeated on the ground in the future.

I only deal in metes and bounds, so in the areas of Texas when dealing with Townships and Sections, many of the same requirements are as in other states. My last survey inside a Township was in 1983 and it was simple as all the monuments were in place.

There are many forms of application that will satisfy the requirements for a metes and bounds survey, as long as there is a defining method that shows an actual bearing and distance between the points that are used as that basis of bearing.

Where is grid north compared to where grid north has been since 1927?