Help me explain this in a different way:
Scenario is a single point static survey submitted to OPUS. While the base station is collecting data, you are out and about collecting RTK points.
You submit your session to OPUS and receive a solution and then take the SPC and apply it to your calibration to get x,y,z of your RTK points.
If you don’t apply the point scale to your 1 point, you are on grid with ground distances to the RTK points, right? Or am I just having a mental issue today.
I think you have it backwards essentially. The purpose of 1 pt calibration is to give you surface coordinates over a small area near the calibration pt. Applying a scale factor on top of a calibration would be taking you away from the surface. A recommended alternative would be to configure the sytstem to the state plane zone. Then if you must adjust due to grid - ground distortion apply a 1/combined scale factor (from the OPUS report) to the state plane grid to translate to ground. We prefer this alternative to calibration. I always like to inspect the scale factor on the OPUS report and decide if there is enough distortion to worry about. Example: Combined scale factor 0.999975 = 25 ppm = 2.5 hundredths in 1000 ft. Does the scope of your project demand such accuracy or are you just planting two bit rebar for property corners? If your scope demands more accuracy you might want to put down you RTK and slowly back away and rethink your process.
I do this all the time, but typically only when doing a topo in a remote area with no vertical control for miles, or if I want to check something that seems funny, or needing to convert local published 29 to now required 88 datums. In Trimblese it's called RTK with Infill to set up the base. The rover is just regular RTK.
OPUS will give you all that great stuff for that one point, including your combined scale. But you want to calibrate to ground, so if you apply the scale factor to the SPC & calibrate to those coordinates you are kidding yourself. You are no longer on SPC. You may as well use 10,000/10,000/OPUS derived Ortho elevation as your N,E,Z.
Another thing is whenever I utilize OPUS I always run it on at least 2 points, then you have a check. They'll usually be within a couple tenths vertically, so pick one and call it good. Horizontally, usually within a few hundredths.
So calibrate horiz & vertical on one point, and horiz only on the other. Now you have a basis of bearing. Ideally they are intervisible so when somebody sets up a total station to stake something, they'll be good to go. Hopefully you won't get that phone call about the 0.04' vertical difference they see.
Good luck
> If you don’t apply the point scale to your 1 point, you are on grid with ground distances to the RTK points, right?
No, you are on grid with grid distances to the RTK points.
That is, assuming the shift was on the order of a few feet. If you are shifting coordinates hundreds of feet you will have errors in the measurements.
