I seem to be unable to get an accuracy on vertical of more than 8-10mm with Trimble S Series robots S5 and S6. Is this the norm for these, am I expecting too much to be sub 5mm? All prisms, rod heights, calibrations etc. are checked and correct so no need to suggest.
Is this as good as they get on vertical? I use to get sub 5mm with Topcon.
At what distance? Is it a repeatable bias or random error,?
Not enough info.?ÿ
1) what accuracy (I have a high accuracy 1" S6, for example)?
2) what length of lines?
3) D+R? How many sets?
4) measure up and measure down (HI and HT)??ÿ
I do trigs using the S6 up to 200 m without any HI's or HT entering in and match differential leveling at the mm level.?ÿ
I don't know what your bugaboo is, but the S series is a very accurate instrument, including verticals. If anything it should be better than a Topcon. You didn't mention tribrachs and tripods. Those can be a cause of error of this sort.?ÿ?ÿ
Another critical question: what prism are you using? I am assuming with autolock? You mentioned calibrations being done - was autolock calibration/collimation done as well?
Adding to this: if you're using Trimble's MT1000 (as a lot of people do) and autolock/tracking, what type of tracking are you using? As discussed relatively recently on this forum, active tracking is known to have some issues with consistent verticals as opposed to the recommend semi-active tracking when you're looking for good verticals.
You name it it has been tested. Two different 5 second robots, all Trimble gear, different data collectors, surveyors, dealers testing, distances, prisms. D&R, sets etc. Same repeatable errors on verticals both robots. I think it is as good as it gets with these.
@john-hamilton "I do trigs using the S6 up to 200 m without any HI's or HT entering in and match differential leveling at the mm level."
Would you mind describing procedure for this?
we do this to transfer elevations between points with large differences in elevation, usually on dams, like in this picture...
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Using the S6 like a level (but not horizontal sights). Setup approximately equidistant from the two points. Use the same fixed pole/prism (HI doesn't matter) at both ends. Turn several sets to each. By doing this the HI and HT do not matter at all. 1" of arc at 200 m is 1 mm. Need to be careful about intervening ground surface that could cause different coefficients of refraction for the BS and FS.?ÿ
8-10mm is an odd number. I've not seen that using my S-6 when I want it tight. Of course, there is a time when you are doing it rougher such as sub-grade stakes then a time when you want it very tight and the S6 I have does it all day long, using the prism/rod, the mini-prism even the 360 prism they all preform well, sub 5mm vertically, not 10mm. This is using the S-6 with Access or Survey Controller.?ÿ
@totalsurv are you shooting to the prism on a pole or on tripod with tri brac? Wore tips on poles can catch you out. Sounds like a measure up issue.
Trimble's MT1000 prism is only good to about 10mm anyway...
Do you get to pick the days you work the deformation surveys ? That looks like a good day for traverse, in that picture.
Traversing in the Forest vertical backsight checks are typically less than 6mm, rarely more. And we aren't trying to get good verticals. That is to a Leica style round prism on tripod/tribrach.
Trimble S6 & S7, 3"
4 sets F1 & F2 (8 pointings 8 distances), target lock mode, standard EDM
This FIG paper has a good breakdown of how various prisms, in particular 360 prisms and specifically the Leica and Trimble workhorse 360s, perform at various orientations and in various modes.
The results shown are consistent with my experience, with both Leica and Trimble gear. There are a few tricks to using the prisms effectively, but once set up they are fairly consistent. Active vs. semi-active vs. passive mode for the MT1000 for sure, and orientation makes a big difference for a couple of the Leica prisms.
That being said, sometimes instruments turn out to be lemons. It's rare among the top brands but it does happen.
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Is it a systematic D&R error? If so probably collimation needing recalibrated. I've seen it several times with Trimble robot verticals. They're usually measuring very precisely, just not accurately.
I have seen them come back from the dealers bench with poor vertical collimation calibration (nearly every time, too).
