Total Station Check and Adjust routines

I took it to my dealer and It was worse than when I took it in when I got it back.
I took it back made him reset it and it was still off.
Got out the manual, did it my self and it's worked great.

I check it occasionally, and it hardly ever changes.
Topcon GPT 9003, Robot

We do our Check and Adjust every 3 months or if we notice something reading 'a bit different'
Unlike most firms we don't have one machine tied to 1 crew, so often you have different machines over the same control which quickly points out if one is recording differently.

Other stuff (plummet etc) is done 6 monthly.

We do them in house, always do them after a service as well. Things seem to get 'Bumped in transit' a lot of the time when coming back from a service.

Hello rfc,

I would perform the built in collimation routine when changing instrument operators because no two operators observe a target in the same way. When I was involved in FDOT right-of-way surveys the instrument operator performed an axis test every day. You should always observe angles using FR/FL to eliminate trunnion axis error. Concerning compensation of systematic instrument errors, we took our total station to the calibration range and adjusted a series of switches under a panel on the side of the instrument to eliminate distance measurement errors.

Regards,

Mark

Hello Equivocator,

May I ask what brand of instrument you use and which company services them?

'Bumped in transit' is a phrase I've heard before. I just want to see if it's the same mob and the same misalignment problem.

rfc,

As far as I'm aware you should check and adjust all of the parameters that the manufacturer deems you worthy of running the routines on. for our instruments this is Hz and V index, tilting axis error, compensator tilt values and ATR offset Hz and V values.

Leica recommends we run the check and adjust in these circumstances:
-Before the first use
-Before every high precision survey
-After rough or long transportations
-After long working periods
-After long storage periods
-If the temperature difference between current environment and the temperature at the last calibration is more than 20°C

If the calibration values are determined accurately I can't imagine what isn't being corrected for that two faces will eliminate. Given the same number of pointings to a target in most surveying situations I don't see why you can't achieve the same accuracy as with pointings in different faces. I'm happy to be corrected though and have my ignorance fought.

Some of my colleagues were doing precision metrology in industrial settings and I don't think they ever turned a second face. All the machines they worked on seemed to work fine when they left.

I've heard that same term used by at least 3 different service providers (and from other surveyors as well.) So I can assure you it's not just the one company using it.

I think it's worth doing the adjustment if anyone, who isn't in the Surveying field, transports an instrument.... and especially after some Surveyors I have known transport it :p

> Hello rfc,
>
> I would perform the built in collimation routine when changing instrument operators because no two operators observe a target in the same way. When I was involved in FDOT right-of-way surveys the instrument operator performed an axis test every day. You should always observe angles using FR/FL to eliminate trunnion axis error. Concerning compensation of systematic instrument errors, we took our total station to the calibration range and adjusted a series of switches under a panel on the side of the instrument to eliminate distance measurement errors.
>
> Regards,
>
> Mark

What's the difference between a "trunnion axis error" and the so called Hz and V index error? They're not the same?

Taken that old girl out to a Calibration Base Line yet?

> Taken that old girl out to a Calibration Base Line yet?

Better do it soon...monitoring them is becoming a thing of the past by the responsible agencies.

I have our instruments set to remind me every 2 weeks. Once you get the hang of it, the longest part of the task is waiting for the instrument to acclimatize. You can use that time to check the tribrachs.

Better safe than sorry.

Yes Scott, or total stations make it to the baseline every year.

How often should this be done, and if done regularly, would this eliminate the need to measure FR/FL for all but the most demanding control surveys

regularly, and no

> How often should this be done, and if done regularly, would this eliminate the need to measure FR/FL for all but the most demanding control surveys
>
> regularly, and no

Thank you. All I need to hear.

Hello MightyMoe,

Once a total station has been correctly calibrated, what instrument errors do you suppose 2-face readings will eliminate that will remain otherwise uncorrected for in observations of the one face?

Hello rfc,

If you are enthusiastic enough, don't take anyone's word for it, try it out yourself. Calibrate the instrument properly. Read a bunch of angles around you to targets, at sufficiently differing elevations, in two faces, with the compensations off. Read several rounds. Reduce your angles. Turn the compensations on and re-read the angles and reduce. Make the same number of pointings in the one face rounds as you did when you were using both faces. Compare. See if your differences are statistically significant.

> Hello rfc,
>
> If you are enthusiastic enough, don't take anyone's word for it, try it out yourself. Calibrate the instrument properly. Read a bunch of angles around you to targets, at sufficiently differing elevations, in two faces, with the compensations off. Read several rounds. Reduce your angles. Turn the compensations on and re-read the angles and reduce. Make the same number of pointings in the one face rounds as you did when you were using both faces. Compare. See if your differences are statistically significant.

That's exactly where I was headed in "Total Station Direction Accuracy--Chapter 5" before I got side tracked into "Calibration". I don't really need to know if the compensations "work" or not; all I need to know is the ultimate practical accuracy the instrument is capable of, which the "Kent Test II" (5 targets, 150'distant, FL/FR measurements all around, then Starnet the daylights out of the results), will tell me.

That said, if I have time before the "soccer kids" show up and take over my test range, I might shoot a round with all compensations off or set to zero, just to see. I don't doubt they'd make a difference; why would the manufacturer have them in there? It is, after all, an electro-mechanical optical instrument. They can't all be identical and perfect out of the factory.

Stay tuned for Chapter 6. 🙂

> Hello MightyMoe,
>
> Once a total station has been correctly calibrated, what instrument errors do you suppose 2-face readings will eliminate that will remain otherwise uncorrected for in observations of the one face?

I know of one: Centering Errors. My manual says that even though the compensators can correct horizontal angles for vertical axis errors, it won't correct centering errors. If the instrument is set up with the vertical axis tilted by 1', that could result in a centering error of about .4mm depending on how high the instrument is set. At 10 meters, that's about 8" of horizontal error.

Here's what the manual says on the issue:

Technically, if the instrument has been (and remains) correctly calibrated, you shouldn't see a difference between the measurements taken with both faces, but there's one way to know for sure: Just DO it!

I know when I did the test with my last instrument, at the beginning, FL and FR readings were the same almost always. As the day wore on (instrument heated up?), they got further apart.

Other than the note above about centering errors, I'm seeing now that routinely using both faces is really a safety net.

Hello rfc,

I'm curious. How will reading 2-faces correct a centering error? Perhaps we have a different understanding of centering error?!?

I was only referring to errors that 2-face readings can correct verses properly compensated 1-face readings.

> Hello rfc,
>
> I'm curious. How will reading 2-faces correct a centering error? Perhaps we have a different understanding of centering error?!?
>
> I was only referring to errors that 2-face readings can correct verses properly compensated 1-face readings.

I partially mis-understood the question and you mis-understood (or I mis-stated) my answer.

1. Reading both faces will not correct centering errors.
2. Calibrating the instrument won't either.
3. Even if the instrument is calibrated properly, reading both faces provides additional surety in the accuracy of the readings, especially because they're done in real time, through out the day; unlike going through the compensation process, which is typically done occasionally.

I'm certainly not an expert on the matter, but it seems easy enough to test how much consistently reading both faces will help, and that's on my list of things to do.