How is everyone dealing with the different Reference Frames: NAD83(86), NAD83(HARN), NSRS2011? OPUS is spitting out NSRS11 and all the CORS Stations ditto. So how about your data collector's NAD83 flavor? And TBC? AutoCAD Civil 3D? Are you noting the Epoch on your Records of Survey? Have I been gnawing my knuckles over nothing?
Dave
davidgstoll, post: 324162, member: 6999 wrote: How is everyone dealing with the different Reference Frames: NAD83(86), NAD83(HARN), NSRS2011? OPUS is spitting out NSRS11 and all the CORS Stations ditto. So how about your data collector's NAD83 flavor? And TBC? AutoCAD Civil 3D? Are you noting the Epoch on your Records of Survey? Have I been gnawing my knuckles over nothing?
Dave
It's not an issue with the DC. The ellipsoid is the same so it's simply the "latest and greatest" false northing and easting. That being said, there was nearly no movement from NAD83(CORS96) Epoch 2002.0 to Nad83(2011)Epoch 2010.0000 so I don't even notice it and that was the projection that OPUS began transmitting when we started using it. For the record, we state what realization of NAD83 we are on just to keep folks clued in 40 years from now.
We don't have any other older NAD83 grid jobs. Everything else was NAD27 tied to whatever monuments we could find because the clients wanted it on NAD27. So, in short, we see zero difference. If the new realization that the NGS puts out makes a large shift (which I don't think it will), THEN we will have to figure out a way (other than rotation and translation) to get back to the stuff from 2000 forward.
Thanks Kris. I've heard there's little difference between CORS96 and NSRS11, but how about the difference between NAD83(86)[Classic?] and NSRS11? I've got some older drawings in C3D, using both Low Distortion Projections and State Plane, in NAD83(86). If I add some OPUS Coords or run my rover off a CORS Station, will I be mixing Apples and Oranges?
Dave
Dave,
Why don't you run some numbers through the chain of:
NADCON (1986 to HARN)
GEOCON (HARN - but it's the "latest" HARN for the state to NSRS2007)
GEOCON11 (NSRS2007 to 2011)
Melita
Melita,
A good idea, but I don't know how to go about getting answers I trust. Civil 3D's HARN and NSRS definitions are wonky. My attempts thus far have failed. And the online NGS "converters" are unfathomable.
Does ArcGIS do coordinate transformations on points? Or is it strictly for GIS stuff?
Dave
Kris,
Great. Now I also have to worry about "Absolute Antenna Calibrations", whatever those are.
"The absolute antenna calibrations may differ from corresponding relative calibrations up to several centimeters so users should ensure they are using the appropriate set of calibration values associated with the particular reference frame that they are working in."
...and IGS and ITRF Frames. Does it ever end? I think I'll just go back to 5000,5000.
Dave
The closest I have to a point converter would be to use a web page based on a geometry service, but it's not straightforward either. I wasn't suggesting mass conversion of data when using the NGS tools, but just a point or two to get a feel for the offsets in your area of interest.
It's not too difficult to get points into a shapefile using ArcMap although you need decimal degrees or projected coordinate values. Create a text file something like:
ID,latitude,longitude
1,34.284729,-117.488291
In ArcMap, under the File menu, select Add Data and select Add XY Data.
Browse to the text file. If you use latitude and longitude for the column headers, the tool should automagically pick them up.
For the coordinate system, the tool will default to the ArcMap data frame's coordinate system. If you want to change it, or the data frame's is unknown, use the Edit button. When you OK the dialog, a layer will be created with the points from the text file.
To save the data as a shapefile, right click the layer name in the table of contents and choose data, export data to start an export tool.
Melita
Depending on what you are doing you are definitely mixing apples and oranges. From Gavin's link:
Be glad you aren't working to the west:
We started with HARN. HARN was good, especially for us L1 users, with limited access to CORS (nearest station to us back then was 60 miles away). The nearest HARN station was 7 miles away. Then we invested in dual frequency gear. OPUS was a diamond. By then CORS96, Epoch 2002, was the standard. Then came NAD83(2011 Adjustment), Epoch 2010. HARN, back in the day, was based on two 4 hour sessions on a monument. We've got hundreds of hours on our own monument "POST". The POST position was determined originally in 2000 by observations to local HARN stations. Then we determined it relative to CORS96, Epoch 2002, which I believe was later referred to as NSRS(2007). Sigh. Am I making any sense?
POST coordinates:
HARN:
N 6835851.505 usft
E 3100685.732 usft
U 402.979 usft
H 96.562m
Texas Coordinate System of 1983, North Central Zone, US Survey Foot, NAVD88
CORS96, Epoch 2002:
N 6835851.443 usft
E 3100685.776 usft
U 403.02 usft
H 96.455m
Texas Coordinate System of 1983, North Central Zone, US Survey Foot, NAVD88
NAD83(2011), Epoch 2010:
N 6835851.451
E 3100685.82
U 402.961
H 96.450m
Texas Coordinate System of 1983, North Central Zone, US Survey Foot, NAVD88
Each were determined by observation, not by adjustment from models.
The CORS96>NAD83(2011) coordinates were in very good agreement with HTDP, meaning that HTDP agreed with the many hundreds of hours of direct observation used to determine the CORS96 position and the NAD83(2011) position.
The HARN position is a little more nebulous. Remember, the HARN were originally based on 2 four hour sessions. By today's standards Whooptie-Doo.
So you're better off, in my opinion, using locally established offsets between HARN and current CORS NAD83(2011), if you want to get all of the goodie out of the transformation.
Our old work, based on HARN, we apply a N -0.054', E +0.088, and U -0.018' shift from HARN to 2011. This was derived internally.
One more thing to note from the coordinates above. Notice that the ortho height remains consistent, even though the ellipsoid height changes fairly substantially. This is a good reminder that Geoid models include both geoid separation values AND adjustments between current ellipsoid values and historic sea level heights. For example HARN ellipsoid height above is a decimeter from the CORS96 and NAD83(2011) ellipsoid heights, but the ortho heights are reasonably consistent. This is why it's important to use a geoid model that is consistent with the NAD83 adjustment being used.
As has been stated, the shift can be significant. The realizations we have used are different by over 10 times our error budget on some projects.
Thanks All! You've been most helpful.
Gavin,
Thanks for the link. I got confused and thought you were Kris. I'm feeling my way around the new site. I miss the "indented" format of the old site.
Dave
Bear in mind that the definition of NAD83 has been the same since day 1 back in well 1983, even though we didn't see coordinates until 1986, thus NAD83(86). Anyway as far as CAD, etc. goes I believe if you set up a project in say NAD83 SPC, the coordinates are going to be whatever realization (I call them flavor) of NAD83 you input into the project.
A lot of software packages may have other picks for NAD83, BUT I believe very few really have any shift or transformation capability, even though they may re-label your output. I say this because NGS nor anyone else has ever published a standard transformation between all of the later realizations where the shifts are minor. NADCON software by NGS (and implemented in various other packages such as CORPSCON, etc.) would do a NAD27->NAD83 and NAD83->NAD83(HARN), after that you are on your own, there is no official way to get further into the future than NAD83(HARN). I know between different HARN realizations like say here in Oregon from NAD83(91)->NAD83(98)->NAD83(CORS96)->NAD83(2007)->NAD83(2011) is a do it yourself project.
The only way to do these transformations is to locally create a transformation in your area by developing your own as Shawn detailed they have done, any off the shelf software that says it is doing these is likely lying to you. In fact I just ran into this with a package I use, the NAD83(2011)->NAD83 transformation is ZERO even though the coordinate output is re-labeled, you need to not fall into the trap of thinking these subtle transformations are really more than a re-labeling effort to make the metadata for GIS input look "right" (at least in most cases these has been my experience).
SHG
Shelby nailed it. I forgot to include the original NAD83(86) which still used classical triangulation in the adjustment (along with new VLBI, GPS, etc. observations). We never really worked with NAD83(86) as the HARN was in place when we started playing with geodetic positions. There's enough noise in the precision of each point in NAD83(86) and HARN that no transformation model is going to be as accurate as a roll your own, in my opinion. Between NAD86(CORS96) and NAD83(2011), HTDP seems to be very accurate, at least in the slow moving North American plate.
I know Topcon Tools will transform any geographic input from WGS84 to the flavor NAD83 you pick. Of course it starts with the erroneous assumption that any geographic input is in fact WGS84, then proceeds to improperly transform everything. When you try to talk to them about it you get that Dorothy feeling when toto pulled back the curtain...
davidgstoll, post: 324182, member: 6999 wrote:
Melita,And the online NGS "converters" are unfathomable.
Dave
Dave,
I'm sorry to hear you find our tools "unfathomable". I grant you they can be improved and we have begun doing so this year, but it is a long process. Still, they are available and are doing the exact job you're looking to do. As such, Melita's advice is sound. However, the connection through the HARN (the post-1986, pre-2007) part of NAD 83 is a bit too "loose" in GEOCON version 1.0 and version 1.1. That has been corrected in GEOCON v2.0, which will soon be on the NGS Beta website for public use.
A quick summary:
NADCON will convert NAD 27 lat/lon to NAD 83(1986) lat/lon
NADCON will also convert NAD 83(1986) lat/lon to NAD 83("HARN") lat/lon
GEOCON v1.0 or v1.1 will convert NAD 83("HARN") lat/lon/h to NAD 83(NSRS2007) lat/lon/h
GEOCON11 v1.0 or v1.1 will convert NAD 83(NSRS2007) to NAD 83(2011)
Notes:
1) Due to the decades of time, and different personnel involved and multiple updates to HARNs, including the FBNs and all the "feathering" between HARNs as they are released, I can not guarantee that "HARN" in NADCON means the same as "HARN" in GEOCON v1.0 (or v1.1).
2) The "HARN" in GEOCON v1.0 or v1.1 really means "the most recently published post-1986, pre-2007 coordinate on a point". This was chosen because there was anecdotal evidence (at the time of the creation of GEOCON) that users were not picky about whether a point was from the HARN, from the FBN, from a mix of the two or even from a feathering to another state's HARN. That is now viewed as generally untrue. Feedback from users indicated a very STRONG sense of user knowledge about the "datum tag" being used on points in their state. As such, when GEOCON v2.0 comes out, it will strictly adhere to only those datum tags which could be considered "supported" by users in that state. GEOCON v2.0 will support rigid transformations from a specific HARN year either into NSRS2007 directly (if there was no significant FBN update to the HARN in that state) or *through* the FBN and THEN into NSRS2007 (in those states where the FBN was a significant update to the HARN). Nonetheless, this rigid adherence to a specific datum tag (year) in GEOCON v2.0 does not guarantee that it will line up with the same data exactly as used in NADCON. That lack of clarity needs to be updated, and should be in the next year or so.
Please look for an announcement about GEOCON v2.0 and know that, at the very least, it will clearly and in a well-documented way, get you from each state's original post-1986 realization into the 2011 realizations in a consistent way.
Dru Smith
Chief Geodesist, NOAA's National Geodetic Survey
Dru,
Thanks for the detailed post, and information on the upcoming GEOCON(11) v2.0!
Shawn,
"So you're better off, in my opinion, using locally established offsets between HARN and current CORS NAD83(2011), if you want to get all of the goodie out of the transformation."
Yes, that's the kind of rubber-to-the-road info I was looking for.
Tom,
"The realizations we have used are different by over 10 times our error budget on some projects."
Let Kent tighten things up for you with StarNet. You'll be golden. 🙂
Shelby,
"...any off the shelf software that says it is doing these is likely lying to you."
I'm already skeptical by nature. But I'm sure now that I don't want to "mix" coords from different realizations in the same drawing.
Dru,
Thanks for catagorizing the different CON's. I'll give them another try, and I look forward to trying out GEOCON v2.0.
Gavin,
I was just kidding about 5000, 5000. I LOVE using the different projections which allow you to bring in GIS Shapefiles and Aerials.
Dave
