Completely Out of Control
I’m not sure if I can describe this correctly but basically, I’ve pieced control together over a 40 acre site for the last 5 years using mostly standard and robotic total station and hopefully growing levels of understanding. I recently got a couple R8-3’s and am playing with them using a TSC3 and Access 2017.
Yesterday I set a job up initially as 1.0 scale factor only and COGO settings set to “ground”, knowing that a site calibration would probably create a transformation. I set the base up over one of the control points (local coordinate system), did the autonomous HERE and did my first HV calibration on our site vertical benchmark. That put my CAD in the ballpark on screen and I went and shot corners and CPs that I had located before. I moved through seven CPs taking ‘observed control points’ on them, then started playing with calibration pairs. I don’t remember when in the process I was prompted for a projection but I do remember accepting Transverse Mercator and setting the geoid as well.
The goal was to check in to as many previously shot corners and control points as I could in an afternoon and see if I could get my gnss control to match (or provide an adjustment to) my piecemeal control.
In the end, the best I can get playing with calibration pairs is that I’m off of all CPs by 0.06-0.18 with a 17.8″ rotation and a SF of 0.99970924 (local CSF is 0.999985… but I don’t think that’s relevant because it’s a calibration calc).
Question is, and maybe I’m answering it by writing this: If I want to export ground coordinates should I eliminate all the calibration points except for the initial “known” benchmark shot? This would presumably bring the SF back to 1.0
Next question is: How best to go about shooting ground distances with GNSS if you’re not shooting on SPC and adjusting in post? Do I calibrate to a single known point, then shoot a corner or two and do a ‘manual’ rotation to get best fit before proceeding (assuming it’s reasonable)?
I think in general I’d like to either spend the time figuring out my own LDP or shoot everything on SPC and translate as needed for mapping.
Unfortunately I don’t own TBC or StarNet yet so can’t even do that very efficiently and, probably like most of you, certain things like this I need to know that I know and when I know that I don’t I live bugged.
Mahalo.
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