I'm sure you are aware of the upcoming move by NGS to go to a national reference frame equivalent to IGS and not NAD83 to be called NATRF2022.
FYI, from as near as I can tell the new NATRF2022 will be accessed through the National CORS that will likely have dynamic values from the constellation much like Yehuda's paradigm at the CSRC. This is different from NAD83 where the National CORS were the realization of the datum on the planet and had nearly zero error and values related to an epoch date. The epoch date of the NATRF2022 will be the date of the survey. From as near as I can tell from easy chair in retirement.?ÿ 🙂
As I think I understand it NGS will provide a correction for tectonic drift, so you won't?ÿ be stuck with that 2 cm/year change in coordinates.
I am not looking at 2022 from the standpoint of creating a reference frame.?ÿ I'm surveying sites and local areas. I want my stuff on the grid to facilitate the use of GIS resources in the design process. I need to establish control for pre-design topo and boundary that will still be there some years later when things go to construction. And preferably still there for many more years so I can hook onto all that work and extend it for the next job across the street and up the block.?ÿ
Relying on ties to a constantly evolving national reference frame to do this may be theoretically possible, but probably just too complicated in practice. The local monument is still king and always will be. From my perspective 2022 will just be another iteration of geodetic adjustment.?ÿ OPUS will report a position and I'll use it. The important thing, for me, is not to mix and match different adjustments.
All this ellipsoid definition, etc. is interesting. For some purposes, not mine, it is really important. But for most of us it will just be another day at the office.?ÿ ?ÿ ?ÿ ?ÿ
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"The local monument is still king and always will be."
Until it is destroyed and not there any more...
"The local monument is still king and always will be."
Until it is destroyed and not there any more...
I'm not talking about NGS brass. I'm talking about the control monuments and boundary marks we all place around our project sites.?ÿ ?ÿ
I have a number of sites where I do biennial deformation surveys (39). Everything is now tied to NSRS. But, having coordinates that change due to reference frame drift is a non-starter. My solution is to have a local tangent plane coordinate system at each site, tied to a stable monument, not a coordinate. So if the NATRF coordinates for a reference monument change, I don't care, the local coordinate (1000N/1000E for example) for that monument stays the same.?ÿ
I could be mistaken, but I thought I read that NGS debated this and for some of the reasons stated above decided to fix NATRF2022 to the North American plate and hold CORS stations, for instance, to an epoch date just as they do now.
With any luck at all I'll be retiring when they roll that out. I don't want to have to explain to people why I can't relate it to Geoid99.
Sorta/kinda.
My understanding is that everything will be moving with ITRF, but they have a model that will remove?ÿalmost?ÿall of the movement on the "stable" part of the NA plate. The NATRF coordinates will be a result of this time dependent model. They want to make as much of it appear to be stationary as possible.?ÿ
But I could be wrong...I have yet to hear (and I have been to many presentations over the last couple of years) a totally convincing explanation.?ÿ
I am looking forward to an updating of CORS coordinates. One thing I do when doing deformation surveys at large dams is bring in GPS for an external "stability" check. But, a couple of the CORS around here are quite a bit off from the published positions, for example PAGW and WVCV. So if I fix those along with others I get large residuals in the adjustment.?ÿ
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Yes, I can compute new coordinates using the time series, but that is difficult to explain to the end client engineers...I really would like to know why these two stations seem to be offset the same amounts from other nearby stations
"With any luck at all I'll be retiring when they roll that out."
I believe that the adoption date of the 2022 datum will be my retirement date. Not 100% sure yet, but I'm leaning that way - 51 years will have been enough for me!
I'm a little disappointed by the lack of clarity regarding dynamic coordinates. Some resources indicate that it will be basically like ITRF, some that it will start at ITRF and then be somewhat stabilized by the Euler pole rotation transformation. But it's still kind of murky.
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I plan to adopt it shortly after it's introduce, however, for those that don't want to make the jump, I think NAD83 will be around for a long time. There are some industries that are still relying on NAD27 today and it's been obsolete for more than 30 years.
(More from the armchair)
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IMO, Geophysicists have different needs than Land surveyors for accessing a recognized reference frame.?ÿ While geophysicists need dynamic coordinates for things like crustal motion, plate tectonics, and possible early earthquake warnings to name a few.?ÿ In most instances dynamic coordinates don't work very well for Land Surveyors.
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Why??ÿ Well quite a bit of the work LSs do is creating topographic maps and laying out construction sites.?ÿ I worked for a big DOT (Caltrans) and we had large projects that benefited from State Plane Coordinates where the curvature of the earth needed to be accounted for.?ÿ So, base maps and top maps were created early in the project and then used by planning, hydraulics, geotechnical, and Design to name a few to create plans for a project to be constructed.?ÿ From the time the original maps were created until the start of the project could be up to and beyond 10 years.?ÿ Utilizing a dynamic coordinate may introduce several feet in error from the plans based on the original mapping.
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Secondly, RW Record maps (maps showing all of the property rights a DOT owns) may have a relationship to a reference frame.?ÿ Continually redoing those maps as a new reference frame or epoch date is created is unrealistic.?ÿ In that instance the best bet is to not use SPCs.
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The subject of dynamic coordinates (not related to ITRF but within a particular epoch date) has been around where I live for some 15 years.?ÿ It came to real focus when Network RTKs started to proliferate.?ÿ Our local Spatial Reference Center was creating a network of continuously operating GPS stations but didn't want to utilize an industry (Leica, Trimble, Topcon) Network RTK solution but wanted to utilize a paradigm that provided dynamic coordinates and elevations on an epoch by epoch basis (1,5,10 sec?).?ÿ That would be good for geophysicists but not LSs.?ÿ So, they would twice yearly meetings on all things Reference Center related.
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Unfortunately, communication of these ideas is not the strong suit of those creating dynamic coordinates.?ÿ At one of those meetings the Director stated that his epoch by epoch values were better.?ÿ So, I asked the question, "how are they better for most of the work land surveyors do?"?ÿ He got red in the face, stormed around, and shouted at me, "I'm not going off on tangents here."?ÿ Needless to say, I was a little confused as to how that was going off on a tangent and completely unconvinced as to what he was trying to communicate.?ÿ Clearly, his listening skills needed work.
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Better communication is paramount.
There are some industries that are still relying on NAD27 today and it's been obsolete for more than 30 years.
The 6th largest city in the U.S. still uses NGVD29 vertical datum...!
Coal mines around here still often use NAD27.?ÿ
The City of Pittsburgh coordinate system is based on NAD (predecessor to NAD27), which is shifted by about 93 feet from NAD27 and about 151 feet from NAD83. That does not mean any of it is wrong, it just means that users must be aware (most are not). Their vertical datum is based on the 1912 adjustment (Sandy Hook Datum), which is 0.266 feet above NGVD29 and 0.275 feet below NAVD88.
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There are some industries that are still relying on NAD27 today and it's been obsolete for more than 30 years.
The 6th largest city in the U.S. still uses NGVD29 vertical datum...!
The Washington Suburban Sanitary Commission uses NGVD29.?ÿ When NAVD88 rolled around they had 50+ years worth of as-built information in 29 and decided that continuity was more important.
The Washington Suburban Sanitary Commission (WSSC) is a bi-county political subdivision of the State of Maryland that provides safe drinking water and wastewater treatment for Montgomery and Prince George's Counties in Maryland except for a few cities in both counties that continue to operate their own water facilities.
The commission is one of the largest water and wastewater utilities in the United States. WSSC serves about 1.8 million people in an approximately 1,000-square-mile (2,600 km2) area. It owns and manages about 10,000 miles (16,000 km) of water and sewer mains
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The City of Portland uses a datum adopted in 1895.?ÿ It's in between NGVD29 and NAVD88 numerically. The City of Vancouver, Washington uses an early local adjustment of NGVD29. Most of the other local agencies (including the counties that Portland and Vancouver are in)?ÿ use a post WW2 adjustment of NGVD29.?ÿ No doubt they will continue to do so after 2022.?ÿ
It should be noted that there is over 3 feet between '29 and '88 around here.?ÿ The provisional 2022 elevations given in the OPUS extended report are closer, much closer, to '29 than to '88.?ÿ?ÿ
FWIW,
The links below provide some information about the issues raised in these posts. SNARF is a project started in the early 2000s to detail approaches to obtain a ??Stable North American Reference Frame.? The first two NGS references are on their web site. The last and most relevant is a link to handouts at a FIG Conference in 2017. You can use this link to navigate to the associated paper. I could not find this on the NGS site.
https://mcraymer.github.io/geodesy/pubs/snarf_gsd2006.pdf - SNARF presentation by Craymer
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https://www.ngs.noaa.gov/datums/newdatums/NSRSModernizationNewsIssue8.pdf - Note section on Euler poles
https://geodesy.noaa.gov/PUBS_LIB/NOAA_TR_NOS_NGS_0062.pdf
http://www.fig.net/resources/proceedings/fig_proceedings/fig2017/ppt/ts05c/TS05C_roman_8841_ppt.pdf - Dr D Roman??s handouts at FIG 2017 in Helsinki
Taken from the Executive Summary of NOAA NOS NGS TR62.
There are a number of sites with information about the maths involved. Search for No-Net-Rotation Reference Frames. As indicated in an earlier post, much of this work is relevant to geodesists and geophysicists.?ÿ
Hope this contributes,
DMM
Thanks, Mike,
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I looked through all of the highly technical links complete with colorful pictures and saw that, IMO, the communication of this change was geared towards phd people and each other.
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I've sat through those types of presentations on a number of occasions and have followed along fairly effectively (Math degree from Berkeley and involved with geodetic survey for decades) and, yet again, think that there is no discussion about the issues related to Land Surveying and no real attempt to reach out to Managers and Executives of organizations that may benefit from it.?ÿ Or guidance documents on big organizations making the change and how, if they do, it affects legacy documents, as-builts, etc.
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It's as if they are talking to themselves or have no interest in communicating effectively to non phd types and those that hang around the edges seem to do so to feel apart of some elite group.?ÿ None of that helps.?ÿ But, hey, they have a committee!!?ÿ
I don't understand the level of angst some folks are having over this change. I have been following this subject for years now, and I don't see?ÿanything SUBSTANTIALLY different than what we have been doing all along. Yeah State Plane Coordinates are going the change, but that happens all the time (out here in the West), and maybe (MAYBE) "some folks" are going to have to do some "extra" studying (most of which they should have been doing all along), but when the dust settles, we will ALL be better off.
I have projects spread all over the Great Basin defined and "controlled" by NAD83 LDP(s), and NONE of those North/East values will change more than MAYBE a millimeter or two (if that).
The Vertical "change" on the other hand is going to be a little tricky for some projects, but it's certainly not the end of the world.
Metadata will be critical, but that has been the case FOREVER anyway.
Just my 2-bits,
Loyal?ÿ?ÿ
I have a fairly low level of angst related to the change. I have a very high level of angst regarding the fact that most of the surveyors in my world have no idea how to deal with SPC's in ANY system. I just read a very lengthy, detailed note concerning SPC's, scale factors, low distortion projection parameters, etc. on a topo survey of a ?ñ0.3-acre lot. The author had absolutely no idea what the note meant or why he put it on the drawing. There aren't any coordinates, bearings or distances shown! This is the norm in area...
I have a fairly low level of angst related to the change. I have a very high level of angst regarding the fact that most of the surveyors in my world have no idea how to deal with SPC's in ANY system. I just read a very lengthy, detailed note concerning SPC's, scale factors, low distortion projection parameters, etc. on a topo survey of a ?ñ0.3-acre lot. The author had absolutely no idea what the note meant or why he put it on the drawing. There aren't any coordinates, bearings or distances shown! This is the norm in area...
I hear ya Jim, I encounter the same thing all the time.
IMO, the level of ignorance?ÿwithin the "profession" concerning State Plane Coordinates (or ANY projection for that matter) is almost beyond belief. It may be worse in some areas of the country than others, but I'm not too sure about that.
Loyal?ÿ
