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Converting between the various NAD83 adjustments
Does anybody know of a conversion program that converts between the various adjustments of the NAD83 datum? Corpscon just gives you 2 choices between the NAD83(1986) and a generic HPGN adjustment. Here in Florida, we went through a number of adjustments over the past few decades (1990, 1999, 2007 and 2011). Any ideas?
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13 Replies
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Javad. You input dates, for ITRF, and the velocities. Tell it. It does it.
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Nate The Surveyor, post: 350091, member: 291 wrote: Javad. You input dates, for ITRF, and the velocities. Tell it. It does it.
The various adjustments should have nothing to do with velocities, should they? Doesn’t NAD83 assumed a fixed plate (unless you are in California)? The different adjustments are just that. In Florida, I believe the 1990 adjustment was the first statewide adjustment with GPS Vectors included, the 1999 was the second statewide adjustment after all of our various countywide denisification projects were done and the 2007 was the nationwide adjustment (not sure what the 2011 adjustment was for).
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How about looking at the NGS data sheets for some HARN/CBN/FBN stations around your area to see how much the superseded values shifted with each adjustment, and interpolate for your desired location.
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Bow Tie Surveyor, post: 350090, member: 6939 wrote: Does anybody know of a conversion program that converts between the various adjustments of the NAD83 datum? Corpscon just gives you 2 choices between the NAD83(1986) and a generic HPGN adjustment. Here in Florida, we went through a number of adjustments over the past few decades (1990, 1999, 2007 and 2011). Any ideas?
Have you looked at the Geocon software at NGS?
Here is the link: http://www.ngs.noaa.gov/web/news/NGS_Announces_Improvements_to_GEOCON_and_GEOCON11_Software_Transformation_Tools.shtml -
Bow Tie Surveyor, post: 350092, member: 6939 wrote: The various adjustments should have nothing to do with velocities, should they?
I guess you are right. I was thinking of something else. I should re-boot me brain more often!
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bow tie,
we use leica geo office software here. it has a module called datum and map transformation. similar to what bill said, above, you can look up the various stations around you and set up an interpolated transformation with that. other software likely has a similar possibility -
Bow Tie Surveyor, post: 350092, member: 6939 wrote: The various adjustments should have nothing to do with velocities, should they? Doesn’t NAD83 assumed a fixed plate (unless you are in California)? The different adjustments are just that. In Florida, I believe the 1990 adjustment was the first statewide adjustment with GPS Vectors included, the 1999 was the second statewide adjustment after all of our various countywide denisification projects were done and the 2007 was the nationwide adjustment (not sure what the 2011 adjustment was for).
I use the published values, then make the adjustment, from NAD83(86) to (2011).
To move from one to another is tricky and for small values it’s going to be very frustrating.
If you want to switch from older to newer control it’s best to do it on-site, just be very, very careful.
Much chaos has been done by people layering new control over old.
You also need to be aware of the differences between HARN in your area and CORS.
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Look at the Beta GEOCON 2.0. I think it has exactly what you’re looking for:
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Dang bowtie, I was looking for the same thing! Good post.
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Bow Tie Surveyor, post: 350092, member: 6939 wrote: The various adjustments should have nothing to do with velocities, should they? Doesn’t NAD83 assumed a fixed plate (unless you are in California)? The different adjustments are just that. In Florida, I believe the 1990 adjustment was the first statewide adjustment with GPS Vectors included, the 1999 was the second statewide adjustment after all of our various countywide denisification projects were done and the 2007 was the nationwide adjustment (not sure what the 2011 adjustment was for).
There are regional velocities along with the plate velocity. The plate velocity is determined by the 14 parameter ITRF>NAD83 shift (7 parameters for dX, dY, dZ, rotX, rotY, rotZ, scale, and 7 parameters for rate of change in each of the first 7). The 14 parameter transformation treats the entire plate as homogenous. However HTDP (Horizontal Time Dependent Transformation) takes into account observed regional motion. When using HTDP, it is important to input the proper NAD83 epoch (ie 2002, 2010) to reflect the proper epoch date for the regional velocities.
You can think of it as being on a boat out to sea. The various elements of the boat remain in the same relative location generally. The front seat is so far from the stern. The transom is so wide, etc. But the boat flexes slightly in reality, so that even though the relationship is generally true, it’s not exact. The HTDP velocities estimate this flexing on a continental scale.
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Hey Bowtie, did you ever figure this one out?
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The latest tool is https://www.ngs.noaa.gov/NADCON5/index.shtml Apparently still Beta?
At the time of the start of this thread, I don’t believe NADCON 5.0 was around, I have checked a couple points and it seems to work well. I believe that this software uses a gridded table of differences to move between flavors, so use with that in mind, but I think for a cm or two it works very well.
SHG
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I thought it came out of beta in December but the website hasn’t been updated to reflect that yet. I can’t find the reference though.
There was an announcement about a beta version of NCAT, NGS Coordinate Conversion and Transformation Tool, that incorporates NADCON5 and these tools:
- XYZ Coordinate Conversion (XYZWIN 2.0)
- Universal Transverse Mercator Coordinates (UTMS 2.1)
- State Plane Coordinates, NAD 83 (SPC83 2.1)
- State Plane Coordinates, NAD 27 (GPPCGP 2.0)
- U.S. National Grid (USNG 2.3)
That announcement was sent out on December 14, 2017.
I’m just one of those evil GIS people. Bwah-hah-hah! Seriously, I do coordinate systems and transformations at Esri.
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