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So an interesting observation while surveying last week in Anoka, MN. During the workflow of bringing in some elevations we recovered (well tried) three MnDOT 3D monuments and only succeeded in recovering one. It was located at the toe of a slope and against the ROW fence. Elevations checked within .08 using the VRS. Not terrible but, not great GNSS Observation environment, and too far to run a level loop and would force crossing Highway 10 at least twice...Fast forward. Decided to run a static point for the BM. Set up an R10-2 and observed for 2.5 hrs.
Upon processing I found some interested results:
OPUS 861.12 (rapid orbits)
VRS 860.97
RTX 861.13 (.to4)
Yesterday, reprocessed OPUS with final orbits:
OPUS 861.09
VRS 860.97, 0.99
RTX 861.12 (.to4)
Scratched my head a bit as I keep getting about .012...Ah Ha! That's right! NGS measures R10-2 ARP at the bottom of antenna mount. So I re-ran everything (static) using the bottom of antenna mount (NGS ARP).
OPUS 860.96
VRS 860.97, .99. .98
RTX 860.98 (red flags galore)
So mystery solved but also confused. Why would RTX not account for NGS ARP setting on the R-10 processing?
OPUS is only as smart as button pusher. So remember a 2m fixed rod is actually 2.05m for OPUS (using R10 Frame). I have to admit, I assumed since Trimble writes metadata to .to4 files RTX would be starter than that when processing static files (sad face).
So note to self, if using RTX as sanity check, be sure to select BTM antenna mount, same for OPUS, don't ASSume.
https://rpls.com/forums/strictly-surveying/r10-antenna-measure-up-point-for-opus/
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
Posted : May 27, 2026 4:48 am
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Why would RTX not account for NGS ARP setting on the R-10 processing?
Doesn't the program have an input field for the antenna height and doesn't that same field have a drop down menu for the method used to measure the antenna height?
I don't believe the program allows for any assumptions on the antenna height, as it should.
Posted : May 27, 2026 8:51 am
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@lurker Yes, it does have drop down, but I was surprised that for static processing to RTX does default to the NGS ARP for the antenna.
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
Posted : May 27, 2026 1:56 pm
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@stlsurveyor
Are you using Trimble online survey tools or Convert2Rinex to submit your files? In either instance, when we submit the T04 from our R12s it does account for the quick release and it outputs the file with the NGS ARP height. I just checked one from the other day to verify.
With the setup I was using my height to the bottom of the quick release was 2.225m, but my submissions to OPUS & RTX via the online tool automatically corrected it to 2.275m. Convert2Rinex also outputs a file with 2.275m in the header.
Posted : May 27, 2026 2:39 pm
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How did you send data files to processing services? Through native websites or through Trimble's "processing services" uploader?
I just sent a file to both OPUS and Trimble RTX today and they both used the same target height. VRS is real-time and probably long base lines from your nearest CORS. I regularly get VRS to OPUS elevations differences of around zero to 3 inches. Because OPUS only used US satellites, I have had 2 projects in the past year that OPUS gave high errors while Trimble RTX returned a good result. So I'm not sure why you list RTX as "red flags galore". Trimble's service is excellent.
When I do a static network adjustment, my position and elevations are usually within 0.1' H&V of OPUS and RTX.
Posted : June 4, 2026 7:42 pm
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@robertusa I got "red flag galore" when I submitted the .to4 file to RTX after changing the ARP to bottom of antenna versus bottom of QR.
The position was collected with a height measured to BTM QR, but when I changed it to BTM antenna the RTX returns matched OPUS (BTM antenna) and VRS but the red flag were flown. I assume this is due to expected versus reality. No questions or concerns about Trimble writ large, I bleed Yellow, but just surprised that a the ARP difference for the QR isn't accounted for in RTX submission from raw .to4 file.
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
Posted : June 8, 2026 7:56 pm