Activity Feed › Discussion Forums › GNSS & Geodesy › Nad27 to nad83 ncat
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@mightymoe i see what you are saying now. That most definitely could be true of points that have moved or whatever. The point was only as good as the last time it was measured. In my case once I reverse engineered there scaling the coordinates it was bang on less than .15 ft most were less than a tenth. Only one was about.15 ft . So ncat was correct and tbc now is. At least in my area. But I ended up not being able to hold the true values as its all relative to the scaled coordinates. But I promise you everything i saved has a big note stating it. It site control not nad 27 or nad 83. Lol.
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3 feet? Check on the US feet, Int’l feet thing before going further.
Ellipsoid, US feet, and why aren’t you just doing a local calibration anyway? Who knows how well they fit the actual datum.
-All thoughts my own, except my typos and when I am wrong. -
@dmyhill I was almost ready to do that. But its very linear and once i started investigating and following what all had been done prior it was easy to figure out. And now its all cleared up and in the clients hands. Hopefully i will get to redo all the control so its correct. I tied it all down and did what was needed.
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I’d be skeptical of creating a custom calibration or transformation unless I had plenty of monuments to go off of. As a general rule if a someone wants NAD27 they are getting NCAT- or TBC-converted values based off of a good, solid NSRS survey, plus a narrative explaining the pitfalls of NAD27.
It’s rare that clients actually, truly need NAD27, and if we can get them in a meeting prior to finalizing the contract, it’s not uncommon to convince them to go with a more reliable datum, or at the very least deliver both current NSRS as well as NAD27.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman
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