Not to be argumentative...
> but my 5" Total Station doesn't suck...
ha ha, I'm sure she's lovely!
Don't worry about the thread title; obviously such a subjective description of a good scientific instrument was a bit tongue-in-cheek.
Mine doesn't suck either....
Except for the software in it. That sucks big time.
Kent, the network adjustment was minimally constrained so the position for each round was recomputed from all available data.
Just about my procedures, I know they aren't optimal. I've tried to strike a balance between precision, accuracy, quantity and reading time. The world below 0.1 mm is probably not as stable as I'd expect (I don't really know though) and I'm just going by gut instinct that I may not collect enough or be stable enough for long enough during a set to conduct perfect testing. Everyone should take it as its offered, which is not perfect.
For a follow up verification I've devised a way to set out a know angle of sub-second precision which will allow me to test a single angle over any section of the circle. But as a billable member of staff it may be hard to find the time to conduct the full scale test in the field, on an overcast day.
On a side note I enjoy your contribution to these threads and the discussion certainly stirs the remaining brain cells I have.
Cheers.
The Leica Patent
From the patent:
>Sources of error, such as, for example, circle graduation errors, can also be determined and appropriately corrected by mapping of the total or substantially total graduated circle coding. In the case of total mapping, a unique code assignment is also always ensured, with the result that—as mentioned above—code elements can be dispensed with. In angle-measuring devices according to the invention, it is therefore possible to use code carriers having less complex codes, which facilitates production and reduces costs.
Why bother if the circles just roll off the production line and are graded? "cool, look a 1" circle, oops now a 5" circle, darn this machine, it doesn't like Mondays! somebody's getting a 5" jigger today!"
The Leica Patent
The more I read patents dealing with angle encoders for total stations, though, I think that patent is probably too new for your instrument. There is an older NASA patent that may describe the circle in the 1100 and 1200 series instruments.
Apparently, there was a major improvement in the technology when an absolute circle design that didn't require reading quite a few different sectors of the circle was developed. It looks as if the NASA design figured out how to code several tracks worth of data onto one.
> On a side note I enjoy your contribution to these threads and the discussion certainly stirs the remaining brain cells I have.
Thanks. I find the test results you're getting fascinating. The more I learn about the circle encoding system that is possibly used, the more I'd suspect that what is happening is that circle eccentricity may be shifting the code on the circle in relation to the reader/detector and the angle error is more an artifact of the reader misalignment.
I don't know whether or not you're read accounts of the Leica TPM used to automatically test total stations and theodolites, but using that, the folks at Leica can run one of their total stations through its paces in about 45 minutes or less and presumably generate really excellent parameters for the software corrections. That is probably at worth at least a grand in value added.
Leica TPM
If the TPM is the machine mentioned in the white paper for the TS30 then yep I've heard of it.
McMillimeter
O.K., maybe that was a poor example:-P
Still holding my sides here, you guys are a tough crowd.
I never thought that I would find myself on the same side as Keith, but the point is, as Maria Muldaur once said:
"it ain't the meat, it's the motion."
By which I think she meant to say:
"It ain't the measurement, it's the monument."
And I believe that Keith will back me up on that...both actually,
Don
Norman,
I would be glad to jump but this one is very long and I am just reading through hitting the highlights now. I could very well jump on the Leica band wagon here and throw out allot of links. I may try to just start a new thread in the next day or so when I have time to focus on what I know about the products I use and sell. There are quite a few Leica white papers that are worth a read. They cover the whole unit from angles, EDM process, and compensators.
I will add a few things on some highlights I have picked out:
1. Instruments like the Leica TPS1200 and now the new Viva TS11 and TS15 are all built the same. They could all be 1 second instruments. It is just the software that controls whether it is a 1", 2" 3" or 5" instrument.
2. All instruments are put through a environmental chamber after initial assembly. This done for many quality control reasons. One of the things is to stress the instrument and then it is placed on a calibration machine to find the individual electronic corrections needed for that instrument. Sort of like a finger print for that instrument.
3. The TPS1200, TS12, TS11 and TS15 have two scanning systems on both the horizontal and vertical cricles. One of the reasons is to measure and circle eccentricities. The TS30, TM30, TS50, TM50 and MS50 models all have 4 scanning systems on both circles to further enhance measuring circle eccentricities.
4. All of the mentioned instruments including older models all have the capability to perform a field calibration on the instrument to determine the needed electronic corrections for temperature changes and physical change in the instrument due to use.
5. The dual compensator actually uses a pool of oil in the system that measures the inclination values that is affected very little by temperature.
The reason for listing the info is just to provide some information towards the discussion. I think the thread has allot of good information and discussion. I always sya that part of surveying is knowing how close is close enough. It depends on the suvey. It is always good to know how to survey anything from +/- 0.01 ft versus say +/- 1 ft.
McMillimeter
> "Measure it with a micrometer,
> mark it with a chalk,
> cut it with an axe."
> An admonition to mantain a consistent degree of precision throughout the analysis, design, and construction phases of a project.
- From the book "Foundation design", by Coduto, Donald P.
> 1. Instruments like the Leica TPS1200 and now the new Viva TS11 and TS15 are all built the same. They could all be 1 second instruments. It is just the software that controls whether it is a 1", 2" 3" or 5" instrument.
Hello surveythemark,
Thanks very much for your input. I'm pleased that it seems my experimentation probably revealed, in some part, real effects from the circle and was not mathematical garbage. I'm not really a fan of the whole "whoopsie! there's a 5" circle" proposition being the SOLE determining factor for instrument accuracy. I think what you said validates that belief, yes?
I ran this software proposition past a couple of Leica techs but they didn't seem to know, or wouldn't confirm it. I hope they didn't think I'd be upset at Leica. We payed for a 5" jigger, we didn't expect to get a 1" model.
And the title of the thread was purposely attention grabbing; I don't think the product 'sucks' as such. I am grateful they all come with the same spec EDM though. All my years of use and testing suggests to me that it is immensely precise.
> I ran this software proposition past a couple of Leica techs but they didn't seem to know, or wouldn't confirm it. I hope they didn't think I'd be upset at Leica.
One thing I'm curious about is whether the H1 and H2 parameters for your 1200 series instrument are separate corrections for each of the two circle reading points or whether they refer to first and second-order (i.e. 2pi and 1pi-radian harmonics) corrections.
McMillimeter
> "It ain't the measurement, it's the monument."
Yeah, but considering there are dang few indestructible monuments it's kind of dumb (or worse) to pretend that the measurements that perpetuate their positions aren't at least equally important.
As for Maria Muldaur, she's now 71, but you can console yourself with her measurements from 40 years ago, right? :>
McMillimeter
> > "It ain't the measurement, it's the monument."
>
> Yeah, but considering there are dang few indestructible monuments it's kind of dumb (or worse) to pretend that the measurements that perpetuate their positions aren't at least equally important.
>
> As for Maria Muldaur, she's now 71, but you can console yourself with her measurements from 40 years ago, right? :>
Good job on googling Maria, but your argument is weak.
Who ever said that monuments are indestructible? Measurments have always been accepted as a poor substitute for reality.
I don't mind at all that people play with math, I've always loved it myself, but don't think that proficiency in manipulating numbers has any relationship at all with boundaries.
Don
It's been a long time since I did it.
My goal was simply to demonstrate that there was a problem with the instrument, rather than quantify the problem. As such my test was quite basic so I didn't have to get too involved explaining it to my equipment supply company.
I simply set two targets (Leica professional circular prisms on legs) about 100m from the instrument and about 90º apart. Instrument and targets were setup in the shade and conditions were good.
Then I turned several sets of angles between them. Once I'd done the first set, I took the instrument off the tribrach, and rotated the base of the instrument 120º and placed it back on the tribrach. Then I turned another set of angles, before repeating twice more - once for the third 120º sector, and once again on the original sector to check for movement.
This meant I had 3 sets of angles, read from different parts of the circle.
I also repeated the procedure at the same time, using the same setup, with an instrument I knew was good (TCRP 1203 3").
The results, as I recall, were very, very clear :D.
Wish I could find my results.
Pretty much identical to the field test that finally showed me we had a systematic 'error' in our 1205+.
Cheers.