@fugarewe this shows why the understanding of the difference between a DATUM and Projection and coordinate system(s) need to be understood at a basic level. Especially state plane coordinates and utm. You might not have said it directly but you indirectly you pulled the wool from the eyes.
You may survey in an infinite number of projections using NAD83(2011). Right there in TBC is an option to create your own. In fact there are two options to do that, maybe there's more, I've only used the default TM projection and the Coordinate System Manager. The underlying NAD83 data in MA is the same as in PA, if I'm understanding your comment correctly.
Why can I survey with the data collector explicitly set to the ellipsoidal NAD83(MA2011) but not the ellipsoidal NAD83(PA2011)?
What DC and version are you using? I don't remember seeing the plate designations in earlier versions, but I always set up templates when the controllers were updated so I rarely looked at the other datums. Trimble cleaned up the datums and zones last year (v2022.10 update), but generally kept the nomenclature.
These days, all the coordinate systems in the NAD83 groups state (2011) without a plate designation:
If you are surveying on the Pacific or Mariana plate, there's no need to specify MA2011 or PA2011 in the controller, because when you set up your base, you input the coordinate that you want everything referenced to, because the computations are still the same no matter what plate you are on.
The controller isn't messing with those values, unless you tell it to by using a datum transformation and a custom system. (Or unless you are doing an RTX survey, which is whole 'nother ball of wax.)
There is an option to apply ITRF to NAD83(2011) to the project. However, when I try to use that option and state plane it seems to simply switch that out and apply NAD83(conus). The Global and Local coordinates are identical so I guess it isn't transforming ITRF to NAD83. Maybe I'm doing it wrong.
I am really confused by all of the varying discussions of reference ellipsoids. WGS84 is the reference ellipsoid for nearly every raw satellite’s reception and all of the CORS station. NAD83 is a coordinate transformation on a different ellipsoid. Lat and Long from autonomous WGS84 positions are EASILY converted to any of the NAD83 adjustments. Autonomous positions can be just as accurate as whatever number your fancy receiver displays. WHERE THE HECK DO YOU THINK ORIGINAL CORS POSTIONS COME FROM. Sorry, I just wanted to make sure you heard me. I may have gotten some nomenclature items above wrong, but the gist of my diatribe is correct.
The "ITRF to NAD83" option disappeared in a recent update to Access.
With the release of TBC 5.90 and the support of NGS NCAT NAD83 transformations under the hood, I am hoping that Access will soon follow suit and allow users to modify the datums during NAD83 job setup. It already does that for the UTM projections, so the functionality is there...
I am really confused by all of the varying discussions of reference ellipsoids. WGS84 is the reference ellipsoid for nearly every raw satellite’s reception and all of the CORS station. NAD83 is a coordinate transformation on a different ellipsoid.
Computations done on the WGS84 ellipsoid are, for all practical purposes, exactly the same as the same comps done on the GRS80 ellipsoid.
Autonomous positions can be just as accurate as whatever number your fancy receiver displays. WHERE THE HELL DO YOU THINK ORIGINAL CORS POSTIONS COME FROM.
A CORS that has been tracked for years and years is a little different than a base receiver grabbing an instantaneous autonomous position and locking it down for the remainder of a day's survey.
In any case, published CORS positions are adjusted, not autonomous, and we typically hold those published positions during processing while perhaps using the short-term time series for standard errors.
Did the earth axis never shift prior to groundwater pumping? One year they say axis shift caused the Ice Age. Another year they say dead dinosaurs and vegetation ended the ice age and started global warming. Later years they say the Ford Explorer exacerbated global warming to the point we had to change its name to Climate Change. Now moving ground water to the surface to transvaporate, has caused the earth to shift back. Should I go buy snow tires for my Ford Explorer since the Ice Age is coming back?
WARNING: Sarcastictic non-politcal humor, I believe none of the above post, hmmpt. I hope Gary doesn't mind me stepping on his post. Without it, I would have not known of that particular scientific thought. It may not appear so, but I found it very interesting.
I am really confused by all of the varying discussions of reference ellipsoids. WGS84 is the reference ellipsoid for nearly every raw satellite’s reception and all of the CORS station. NAD83 is a coordinate transformation on a different ellipsoid.
Computations done on the WGS84 ellipsoid are, for all practical purposes, exactly the same as the same comps done on the GRS80 ellipsoid.
Autonomous positions can be just as accurate as whatever number your fancy receiver displays. WHERE THE HELL DO YOU THINK ORIGINAL CORS POSTIONS COME FROM.
A CORS that has been tracked for years and years is a little different than a base receiver grabbing an instantaneous autonomous position and locking it down for the remainder of a day's survey.
In any case, published CORS positions are adjusted, not autonomous, and we typically hold those published positions during processing while perhaps using the short-term time series for standard errors.
Both start from an autonomous postion. It is the same thing, just a longer observation time. 15 minutes of static is the same as 2 hours of static, just longer and more precise. Autonomous positions are just as accurate as a NAD83 position, its just the value that is different.
Where did that original CORS value come from? Of course it is adusted, just like your traverse gets adjusted. The value may change, but it is still just a nail in the dirt measured with the same two angles and same two distances.
The CORS Stations that I use get revised annually from new autonomous postions.
@oldpacer Concept seems reasonable enough. Take a spinning ball and redistribute a significant portion of mass from a small area to all areas of the system and this should cause a change in the axis of rotation. i would think it would simply be a calculation of the mass needed to cause x amount of change. Someone probably can't directly attribute the pumping of ground water to the change in the axis of rotation but they certainly could model the amount of mass needed to be moved in order to cause the change.
@lurker I had to stop thinking of all of the varibles, my head was starting to hurt. Compensating magma movement, China population, tidal redistribution pulling the moon out of orbit, all of my control points no longer accurate. Blam.
I wonder about volcanic eruptions. It could be argued that magma stays earthbound, but there's a heckuva lot of water vapor and gases being thrown out, too. Ash that was concentrated in a small space is redistributed worldwide.
But maybe the solution is to have farmers 180 degrees around the earth from our midwest to draw out an equal amount of water.
Both start from an autonomous postion. It is the same thing, just a longer observation time. 15 minutes of static is the same as 2 hours of static, just longer and more precise. Autonomous positions are just as accurate as a NAD83 position, its just the value that is different.
Where did that original CORS value come from? Of course it is adusted, just like your traverse gets adjusted. The value may change, but it is still just a nail in the dirt measured with the same two angles and same two distances.
The CORS Stations that I use get revised annually from new autonomous postions.
I think we are discussing two different things. I'm not against using autonomous positions, and I don't disagree that autonomous positions will converge over time. (They can, however, bounce around a lot more or a lot less depending on where the receiver is and local conditions.) I was focusing on the implications of selecting one system vs another in the software.
The NGS doesn't typically revise NCN positions on a yearly basis. Usually it's only when a new antenna is installed, or it drifts by several cm. Are you using local/state CORS?
I wonder about volcanic eruptions. It could be argued that magma stays earthbound, but there's a heckuva lot of water vapor and gases being thrown out, too. Ash that was concentrated in a small space is redistributed worldwide.
But maybe the solution is to have farmers 180 degrees around the earth from our midwest to draw out an equal amount of water.
Austrailia could become a rainforest again, all in the name of saving the planet.
Both start from an autonomous postion. It is the same thing, just a longer observation time. 15 minutes of static is the same as 2 hours of static, just longer and more precise. Autonomous positions are just as accurate as a NAD83 position, its just the value that is different.
Where did that original CORS value come from? Of course it is adusted, just like your traverse gets adjusted. The value may change, but it is still just a nail in the dirt measured with the same two angles and same two distances.
The CORS Stations that I use get revised annually from new autonomous postions.
I think we are discussing two different things. I'm not against using autonomous positions, and I don't disagree that autonomous positions will converge over time. (They can, however, bounce around a lot more or a lot less depending on where the receiver is and local conditions.) I was focusing on the implications of selecting one system vs another in the software.
The NGS doesn't typically revise NCN positions on a yearly basis. Usually it's only when a new antenna is installed, or it drifts by several cm. Are you using local/state CORS?
NGS and CORS Station are two differents things on two different ellipses. Go to a CORS Station that you use. In the archives, you can find the value they used last year and the year before. If reprocessing old data, you need to use that years data. I am not trying to be a butt, I do a good job of that without trying, but there is info in this overall post that I dont believe to be accurate, or more exactly, not stated correctly.
FWIW, any visit to Australia should include visits to the Gondwana Rainforests. Lovely, lush, verdant with abundant wildlife.
Wooah, had no idea. See what a little groundwater will do.
I did not realize this was an old post. There are broken links embedded in some replies.
For the Helmert transformation parameters used by the US NGS for NAD83 #### to ITRF #### see: https://geodesy.noaa.gov/CORS/news/historical_helmert.shtml
NGS and CORS Station are two differents things on two different ellipses.
There may be other CORS from sources outside the NGS, but there is a single NOAA CORS Network (NCN).
The NGS does not change the published values for the NCN every year. They spell out pretty clearly under what conditions those values might change.
Go to a CORS Station that you use. In the archives, you can find the value they used last year and the year before.
The nearest NCN CORS to me is SEDR. Its value has been modified three times per its coordinates page link.:
If I pull data for SEDR from three years ago, the .DS datasheet I get has the exact same coordinates as it does today. The RINEX header has the same information.
The short-term and long-term time series shows how the daily solution compares to the published solution, but the published solution is not being modified year-over-year. It explicitly shows their variation with respect to the last adjusted position (MYCS2).
Now, if we are talking OPUS solutions, those positions are computed in ITRF (currently ITRF2014) at the current epoch (technically the middle of the observation) and transformed back to NAD83(2011)[2010.00]. But that's a different application and a different workflow.
As autonomous positioning relies on the broadcast ephemeris, users interested in its accuracy might want to view this article: https://iopscience.iop.org/article/10.1088/1757-899X/631/4/042013/pdf