Additive Constant

Maybe the Check & Adjust?

How accurate were your temperatures??

Or maybe you can correct the 2mm with a bogus temp setting?

An error in temperature manifests as a PPM error (i.e. scale), not an additive error. But, shooting between two points only it is not apparent if it is constant offset or scale. To check for a constant offset error, set 3 points inline (distance should be small to eliminate any scale error), then shoot all three distances (i.e. A-B, B-C, A-C). The constant error (which ALSO INCLUDES ANY ERROR IN PRISM OFFSET) is AC-(AB+AC). This works best if you know for sure what the prism offset is. 

We actually went to a CBL yesterday as required by a contract. We consistently get a 4 ppm scale error. This baseline has 4 pillars, so there is no centering error. Here are results using two different instruments over the last few years. 

I also took the same S6 to the baseline at NGS Corbin and got -1.0 ppm and +0.0003 m constant error. 

So I believe that the baseline has a slight bias. I will note that it is set on the downstream side of a large earth dam with a water reservoir behind it, so the weight of the dam and the water behind it could have caused some deformation. The line is between the road and the earth dam on the south side of the reservoir. 

Note that 1° C (1.8° F) error in temperature causes a 1 ppm error. Temperature varies slightly near the ground, so it is difficult to get near 1° C accuracy

@landbutcher464mhz 

Temperature introduces a ppm error, not a constant.

Posted by: @micheal-daubyn-2-2-2-2

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I generally do my own servicing, so I'm hesitant to send the instrument in for service.

Just how are you doing your own service?

What is the pedigree of the TS16.  Did you purchase it new or used.  If it was used, I would definitely want to have it in for a checkup and cleaning.

The regular servicing is just a cost of doing business.

You can adjust all of your prism constants by 2.03mm but it won't change any reflectorless shots, assuming you're seeing the difference there also.

@lurker I did consider that, but for the amount of frustration it would introduce into my life I think I would rather pay for the service.

Posted by: @john-putnam

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The regular servicing is just a cost of doing business.

I would agree with that if I thought the price was appropriate. Unfortunately, I'm am in Oz, and we only have one authorised Leica dealer for the entire country. And trust me- they price accordingly. Even NZ has more than one authorised dealer.

As far as I am concerned, if the instrument passes the baseline and runs true after a check & adjust cycle, then it is only a matter of lubricating the gears and worm drive(s) on the servos. That's what I do. If you are brave enough and careful enough with the seals on the side covers then it isn't such a big job.

Mick

Posted by: @landbutcher464mhz

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How accurate were your temperatures??

As mentioned, my error was picked up by eye and confirmed via the EDM baseline calibration spreadsheet. We took atmospheric readings at each end of each pillar reading. My error is a constant, and therefore not introduced by any temperature error. 

Mick

Posted by: @timd1971

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Maybe the Check & Adjust?

I searched there. There is nothing EDM related.

I'm pretty sure that the only additive constant setting would be as a prism type constant.  I haven't checked on my TS16 yet, but suspect that, like my old Topcon, there is the ability to edit existing target profiles or create custom profiles.  That's where you'd account for an additive constant.

As far as I know the instrument constant is set at the factory and should not change unless the instrument is damaged. But I could be wrong. 

I would do the three point test I mentioned above to see if the prism offset is correct. Keep the distances short and no scale bias will enter into it. I found that our -30 seco mini prisms are actually -29. And our -40 Trimble monitoring prisms are indeed -40. 

Posted by: @john-hamilton

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I would do the three point test I mentioned above to see if the prism offset is correct. Keep the distances short and no scale bias will enter into it. I found that our -30 seco mini prisms are actually -29. And our -40 Trimble monitoring prisms are indeed -40.

Looks like he already went to a baseline to do that: (from OP) "I ran the TS16 over an official 7 pillar EDM baseline and ran the data through the spreadsheet and my issue was confirmed- my TS16 has an additive constant issue of 2.03mm."

@john-hamilton The AC is adjustable - and needs to be adjustable - to cancel out manufacturing flaws or discrepancies. The question at hand is whether or not the end users has access to that adjustment. It's beginning to look more and more like we don't.

Regarding the prism issue, I mentioned in my original post that I ran the instrument over a 7-pillar baseline along with a buddy's TS15. The spreadsheet that you enter the raw obs into spits out the corrected prism constant as well as the AC. Only my instrument had the AC error. The TS15 did not. Again, my TS16 also measured long compared to my own TS15 and two of my 1200s. The prism is fine. I have a constant error that is not related to a prism constant.

@eapls2708 I think calling it an additive constant assumes that the prism offset is correct, which may not be the case

Posted by: @micheal-daubyn-2-2-2-2

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Even NZ has more than one authorised dealer.

No, just Global Survey for Leica gear. ~1k per robotic total station service, takes them a day per instrument.

@lukenz I thought CRK were in Auckland as well?

For NZ$1000 it would be cheaper for me to fly across the ditch and do it in NZ........even with airfares and accommodation.

@john-hamilton

a) The fact that I compared 4 instruments means that it actually doesn't matter if the prism constant is correct or not- the TS16 shoots long, and it is a constant. The prism constant could be zero, -34.4 or +34.4 and it wouldn't matter over a single baseline. The TS16 shoots long.

b) The spreadsheet I use differentiates between the prism constant and the additive constant. You don't actually tell it what your prism constant is. The spreadsheet figures it out.

c) The TS15 that ran over the EDM baseline with my TS16 produced a result suggesting the prism constant was the same as mine (it was the same prism for both instruments of course) but its AC was hovering around zero mm while the TS16 was a tad over 2mm.

@micheal-daubyn-2-2-2-2 

Looks like they are but not selling survey gear based on the website.  I thought ~1k a service was a fair wack, what do they charge your side?