"I guess you are doing the obs to submit to OPUS projects."
Yes, and running into all sorts of glitches with the GVX files coming out of Access, plus some as-yet unexplained import problems on the NGS side. NGS staff have been great in helping me debug the process, though.
You may want to take a look at this video, jump to 7:30, to find out something very interesting about Trimble's RTK 'multiple epoch' observations:
I'm not sure what he's saying.
He's saying the Trimble people told him that despite being stationary for xxx epochs of RTK measurements, only the last (best?) measurement is being stored.
Which is why it's a good idea to log raw data at the rover. Especially if you're doing long(er) epoch collection.
At least you can post process that data as a check, and it's usually better quality than the RTK shot.
"He’s saying the Trimble people told him that despite being stationary for xxx epochs of RTK measurements, only the last (best?) measurement is being stored."
I'm skeptical. Why would Trimble even have an "observed control point" category if they're having you sit on a point for 3 minutes but only storing the last epoch?
With my Javad gear, all of the epochs are weighted and go into the solution, and you can watch the resulting position change as each epoch is collected.
Yeah that's strange. Why am I sitting there for minutes when I can apparently get the same data in a few seconds?
It's 2024 and there are videos for surveyors on how to do a site calibration?
I started watching and thought it was 1996 again.
As far as the observed control RTK point. If I ever was going to do a something as regressive as a site calibration it would only be done using static data.
Site Calibration, Holy Moly.
How is that still a thing?
How about you explain to all of the plebs how you do things since site calibrations are apparently so bad.
I'm with @MightyMoe on this one. a properly setup site shouldn't require a calibration. We haven't calibrated for a very very long time. I do understand the need for it though, but that seems to mainly be driven by the software, especially for the machine grading gps setups.
The Trimble method you are skeptical of is very nearly the same thing as the Javad process.
A "Kalman Filter" is basically the name of the process that you describe for Javad.
The math of the solution improves as the algorithm iterates, and converges on the "best" solution.
In Trimble, you just don't get to see it or review it.
Javad is still storing a single position of the solution generated by the weighted measurements, just like the Trimble.
In GNSS processing, resolving the fractional part of the pseudorange was quite easy and very precise. Being sure of the whole number of wavelengths was more difficult. That's what "Fixed" used to mean, we know the whole number of wavelengths in the pseudorange, and thus we had the distance to the satellite, for any given number of satellites. The "position accuracy/precision" was not really considered.
Current RTK GNSS positioning solutions have moved away from the "Fixed/Float" nomenclature because those terms were arbitrary with respect to the accuracy/precision of the position, but made the user feel better. Current survey grade tools now reflect the measurement convergence of a solution on the most probable position with the accuracy/precision of some statistical measure with respect to many other variables that affect precision/accuracy, like all the DOPs.
He’s saying the Trimble people told him that despite being stationary for xxx epochs of RTK measurements, only the last (best?) measurement is being stored.
Yeah....that's absolutely incorrect and "Trimble people" probably means "rando dealer person". A glance at the data in TBC will show the number of epochs in the vector solution.
For observed control points, the number of epochs set in the survey style must be met sequentially, and all of them must be within the tolerances set by the user. If it's set to Auto, Access uses the expected precisions from the connected receiver, and if there are user-defined tolerances, those will be overridden.
For topo observations, there are two conditions that must be met for storage, time and number of epochs. The receiver must collect for the time specified, plus the number of sequential epochs that meet expected precisions.
With my Javad gear, all of the epochs are weighted and go into the solution, and you can watch the resulting position change as each epoch is collected.
Same thing with Trimble, although you don't see the final position changing during collection, only the realtime precisions.
@WA-ID Surveyor I was told early on that the systems running machine control needed to calibrate, I've also been told that more recent systems can handle projections and geoid models. I don't know enough about their equipment to say. So apparently machine control may or may not need to calibrate. That doesn't mean the surveyor does.
What we do is give out control for their construction purposes. It seems to work well, as long as my control is tight to their machine data all is good. So far everyone is happy. None of my control is ever calibrated so we don't need to do anything. I've got a dozen subdivisions in various stages. The first job is boundary and everything is tied to our projection data and everything follows from there. If the construction company wants to calibrate, that's on them.
But, any XYZ data can be projected to a geodetic system if the internal geometry and elevations are accurate, if it isn't then it's of no use anyway and needs to be scrapped.
Some years ago Dr. Herb gave part of a seminar about how to do it.
The violence done to the data by a calibration isn't necessary anymore with modern Geoid models.
Another thing...
Since you intend to submit RTK vectors to OPUS Projects, you will probably want to set your survey stlye up to record the QC2 (variance/covariance matrix) associated with the recorded rtk vectors.
QC1: DOP & Time.
QC2: Variance/Covariance Matrix.
QC3: Error ellipse(derived from QC2).
This may help:
https://help.trimblegeospatial.com/TrimbleAccess/latest/en/Home.htm
And back to your original question about precision warnings:
https://help.trimblegeospatial.com/TrimbleAccess/latest/en/GNSS-survey-messages-and-warnings.htm
QC1 & QC2 is stored for all vectors (except Rapid) by default.
He indicated he was using a rental.
No telling how that thing is set up.
