Rather than deliberately degrade excellent observations, isn't it more likely that a less effective and hence cheaper sensor is used to read the circle.
Why would a manufacturer build a universal system and then degrade its ability to function in order to make less money?
:-S
Scott Zelenak, post: 374367, member: 327 wrote: Rather than deliberately degrade excellent observations, isn't it more likely that a less effective and hence cheaper sensor is used to read the circle.
I don't see why. If this were the case then the difference between the 1" and 5" model should be the cost difference between a 'cheap' and 'less cheap' linear 128 pixel CCD/CMOS array. The cost difference between Leica's 1" and 5" model FAR exceeds any extra cost that using a less-cheap CCD array would add. What do you imagine the price difference between 2 slightly different quality linear CCD arrays is? you can buy a fully functioning, whole camera with millions of pixels for well under a hundred dollars. I can't imagine the volume cost of the sensor would be represent much of that price.
Why would a manufacturer build a universal system and then degrade its ability to function in order to make less money?
:-S
Well they don't have to. And I'm sure the other instrument manufacturers will be more than happy if one of them left the 5" segment of the market alone. If satisfactory margins are still there on your universal instrument when sold as a 5" model then why wouldn't you increase your exposure, market share, turnover, profits etc. by going after the 5" segment of the market? How are you making 'less' money then? Not everybody who would purchase your 5" model at a 5" price will bear the not-insignificant price increase to purchase your 1" model if it were the only one you made.
A accurate anglular value is intentionally down graded by introducing an error? Unless the manufacturer stated that, proving that would be hard, a NIST level problem.
Larry Scott, post: 374372, member: 8766 wrote: A accurate anglular value is intentionally down graded by introducing an error? Unless the manufacturer stated that, proving that would be hard, a NIST level problem.
Proving any unique position regarding the undisclosed method used to produce an instrument that slots neatly into a specification would be a NIST level problem no?
I'm probably unique in here in that I've actually had a crack at it. And taken a position, which is arrived at through research and experimentation. At least on the Leica 1200 and TS15 series instruments. I can't speak about other manufacturers strategies for providing different specifications.
I don't know what you'd consider an NIST level effort, but I've put in more effort than most chasing the real errors in our company's own total stations. I posted a great deal of my methods and findings here in various threads to support my conclusions. They were also seemingly confirmed by a poster here called surveythemark(?) who was/is a Leica tech/sales person (or something) who stated something along the lines of: the instruments are manufactured to the same spec and it's the software that determines whether they are sold as 1", 2", 3" or 5" models. I hope I'm not misrepresenting or misunderstanding his post from about a year ago.
Upon review i think it would be more like a post-graduate uni student problem to test the accuracy of the encoder as suitably accurate angle-reading setups exist against which to compare the encoder track's accuracy. For example, a google search will turn up a paper testing the errors in the angles produced by a Leica laser tracker by comparison with another, higher accuracy encoder setup. If then you managed to confirm the accuracy of the encoder you'd have to dream up some scary mechanical scenarios to explain a regular, repeating, ever present, sinusoidal directional error (again, I'm speaking Leica specific).
I apologize. I'm sure you're applying a high science. And measuring a hundred angles to the marks on an Invar leveling rod, many times, may show a pattern.
And I realize that the plates are probably all made in the same process to be 1" grade. And failing testing, they would be used in a lower order gun, and to be consistent, a series of rounding off may be req'd to be consistent.
Micro radians are tough to hold on to.
Larry Scott, post: 374377, member: 8766 wrote: I apologize.
Even if facetiously, apologising for what?
Perhaps you misread my tone or intent. Talking about this stuff on the Internet now is good sport and nothing more. I was taking the time to fully lay out my position to you as you seem like a tester yourself and might get something out of it. none of that post was a veiled or direct dig at you, your knowledge or experience.
Micro radians are tough to hold on to.
im sure they are
Conrad, post: 374378, member: 6642 wrote: Talking about this stuff on the Internet now is good sport and nothing more. I was taking the time to fully lay out my position to you as you seem like a tester yourself and might get something out of it.
One of the nicer refinements of your test method was the design of the targets you employed. As I recall, it was basically a line that changed thickness in discrete steps, sized so that one fo the steps would match the space between the split wires in the instrument reticle. Would you be willing to post an image of those targets you used? Was it essentially just a thin wedge that the printing process reduced to pixelated steps?
Now that I think about the problem a bit more, the simplest approach would be to use my Zeiss Th2 (assuming the lubricants on the motions haven't stiffened too much since I last used it more than a decade ago) to calibrate a target array to values with standard errors of about 0.5" and then compare the Sokkia CX-105 to reality.
The one refinement would be to have a fixture by means of which the CX-105's mounting can be rotated about the same center +/-0.1mm.
Conrad,
I follow your thinking in reply to my post but not the manufacturers thought process involved in instrument specifications.
If any manufacturer could produce 1" instruments at 5" instrument prices, why not dominate the market with 1" instruments at 5" instrument prices?
I should have taken more business courses in college...
John Wetzel, post: 374337, member: 11747 wrote:
All the digital total stations I ever used had separate upper and lower motions, and wrapping angles on those works very well to get angles that are at least twice as good as the least count, and you only need to wrap the angles four or five times (direct or direct and reversed depending on how good your controls needed to be).
I've never heard of that. Is there any way to know whether my GTS 255 has such "upper and lower" motions? I've always thought modern total stations just had one disk of glass for each axis.
Conrad, post: 374350, member: 6642 wrote: Kent, as I mentioned unthread, I now believe (due to more looking since my testing ended) the circle is pure, and that the 'errors' are injected by software alone. Something like:
Hz(display)=Hz(pure)+sin(multiple*Hz(pure))*[amplitude]
Where [amplitude] is the desired spec.
Conrad:
I've re-read that fabulous thread on your tests. The bottom line, it seems is that one might not even need to hack the manufacturer's firmware (which would most likely be illegal anyway), to gain the benefit of the higher precision capability; If one knew physically where on the instrument the crossing of the "sine wave" was, would not one only need to set the horzontal to zero, then post process all directions by the formula?
I understand that it'd be a lot of work, and of academic, not commercial value. It'd probably be more cost effective to just pay the manufacturer to do it (by reason of buying a 1" instrument).
It sure is fascinating though.
Obviously too much time on my hands today....
What would be the reason a manufacturer could not produce (at least to the limits of human sensibility) a zero second instrument?
Scott Zelenak, post: 374421, member: 327 wrote: Obviously too much time on my hands today....
What would be the reason a manufacturer could not produce (at least to the limits of human sensibility) a zero second instrument?
Good question, but why does it need to be limited to human sensibility. I thought no one looks through total stations any more, opting instead for the robotic type. If lasers are talking to the targets, why couldn't things get down to the 1" region?
rfc, post: 374410, member: 8882 wrote: I've never heard of that. Is there any way to know whether my GTS 255 has such "upper and lower" motions? I've always thought modern total stations just had one disk of glass for each axis.
If you only have one motion in the horizontal axis, it's an upper motion. A 'set' instrument.
A two motion instrument (in the horizontal axis) has an upper and lower like a T1.
Scott Zelenak, post: 374408, member: 327 wrote: Conrad,
I follow your thinking in reply to my post but not the manufacturers thought process involved in instrument specifications.If any manufacturer could produce 1" instruments at 5" instrument prices, why not dominate the market with 1" instruments at 5" instrument prices?
I should have taken more business courses in college...
hey Scott, I didn't study marketing or business so I'm just spitballin'. But I don't accept the premise of a 5" instrument production cost; as if somehow it is even a noticeable difference at large volumes to 1". Or that it could be cheaper when compared to the costs of having unique tooling and maybe unique assembly lines. If you aren't tooled for the different models then we're back to the only difference being a few component specifications.
If you are going to manufacture instruments that truly are sorted based on mechanical imperfections then you will have some that don't meet your lowest spec. And you've just blown the whole cost of producing something you can't sell if you only sell 1" instruments. There isn't a market for 5" garbage anymore in your world; you killed it!
It seems self evident to me though that there exists a whole range of people with a whole range of finances willing to pay a whole range of prices for differing reasons. Why leave all that money in their pockets? And why then engage your other established, well-credentialed and capable competitors in a race to the bottom? I'd imagine all of them can do the 1" model just as easily. You aren't guaranteeing yourself anything in the way of market share because they'll do the same in your world.
Besides, if you do that then apple will probably come in and start producing iStations: 0.9" Instruments in rose gold, in perfect white boxes designed in california that open perfectly, and laugh at you while selling them for 10x what you do.
rfc, post: 374413, member: 8882 wrote: ...If one knew physically where on the instrument the crossing of the "sine wave" was, would not one only need to set the horzontal to zero, then post process all directions by the formula?
Set to zero, or not. If you know where it crosses (and i do by way of simple pen marks on the upper and lower halves) then you can pos-process (like me) against the circle reading at your crossing. You just subtract the circle reading at the sine zero crossing from your other processed directions while post-processing. For me it's better because I work with azimuths in the field; I don't want to be using absolute circle directions.
Kent McMillan, post: 374401, member: 3 wrote: One of the nicer refinements of your test method was the design of the targets you employed. As I recall, it was basically a line that changed thickness in discrete steps, sized so that one fo the steps would match the space between the split wires in the instrument reticle. Would you be willing to post an image of those targets you used? Was it essentially just a thin wedge that the printing process reduced to pixelated steps?
this is my 'stepped A'
The intention was that at there would be a gap somewhere up or down the target that would be a perfect fit at any distance. In practice you only need a few steps if you know the ranges you will be sighting at. I'd have preferred a slim, smooth triangle target to sight at but my printer wasn't capable of the resolution I wanted to produce a visually smooth diagonal at the ranges I was working at .
These 'stepped A' targets were sufficient, but I kept looking for better and the last ones I was using were just black blocks separated by white spaces of varying width. I'd produce a small group targets with varying widths, pick the best width from the instrument and scribble out the others in that group. The scribbling out also was useful in that the pen scribble gave me something quite fine and textured to focus to. I wasn't able to detect distance-dependant errors due to focusing and didn't attempt to model them either. To be honest, I'd landed in 'precision crazy-town' and didn't think about pushing it any further. For example, here is my final error fit for our TCRP1205+ R1000. The standard deviation of these residuals to the best fit curve is a bonkers 0.18".
Conrad, post: 374465, member: 6642 wrote: this is my 'stepped A'
The intention was that at there would be a gap somewhere up or down the target that would be a perfect fit at any distance. In practice you only need a few steps if you know the ranges you will be sighting at. I'd have preferred a slim, smooth triangle target to sight at but my printer wasn't capable of the resolution I wanted to produce a visually smooth diagonal at the ranges I was working at .
Yes, that was the target design I thought I remembered. Very well adapted to minimizing pointing error over close-range sighting distances. It's a keeper.
Conrad, post: 374465, member: 6642 wrote:
I wasn't able to detect distance-dependant errors due to focusing and didn't attempt to model them either.
Conrad:
1. How tall are those? Did you print them on a laser printer and attach them to something?
2. Your statement about distance-dependant errors raises a question I've been meaning to ask for a long time, but never got around to it:
Is the EDM in a modern total station dependent on the optical focus of the gun? Is that what you're referring to above?
rfc, post: 374484, member: 8882 wrote: Conrad:
1. How tall are those? Did you print them on a laser printer and attach them to something?
From memory they wouldn't be more than 5mm tall and they were printed on a cheap laser printer and stuck to the brick wall of the Conrad Precision Measurement Laboratory/Garage.
2. Your statement about distance-dependant errors raises a question I've been meaning to ask for a long time, but never got around to it:
Is the EDM in a modern total station dependent on the optical focus of the gun?
No I don't believe so. I believe the path that the EDM signal takes through the telescope is all in front of the focusing elements.
Is that what you're referring to above?
No. I'm referring to the kind of error you'd get if the line of collimation of the crosshairs were not intersected perfectly in space by the standing axis of the instrument. This would mean that you'd be observing from a position offset (eccentric) by some distance from the standing axis. At longer distances you'd create an angle so small between the crosshairs, target and the standing axis it'd be undetectable but at shorter ranges you'd see it growing. If you sighted targets at progressively closer distances in face left and right, and noted the differences you might see them growing as the target got closer. Weighting direction observations in a least squares adjustment by including a centering error would effectively mask the growing, one-sided bias of this kind of systematic error in a single faced half arc, and reading two faces should eliminate it, but if you wanted to be hardcore you could attempt to map it and remove it before adjustment. Also adjusting the focus of the optics can apparently result in collimation changes within the optical train.
I think you might get something out of this paper
https://www.fig.net/resources/proceedings/fig_proceedings/fig_2003/TS_12/TS12_3_Martin_et_al.pdf
rfc, post: 374413, member: 8882 wrote: If one knew physically where on the instrument the crossing of the "sine wave" was, would not one only need to set the horzontal to zero, then post process all directions by the formula?
I understand that it'd be a lot of work, and of academic, not commercial value. It'd probably be more cost effective to just pay the manufacturer to do it
No actually it was more cost effective to have me do it as the boss paid me nothing to do it! But I don't mind; it was a good learning experience.
The post processing is of very much, real world value to us and, with my spreadsheet, takes just minutes at most for a days work. Just thismorning one of the other surveyors reported before and after miscloses on a job of 40mm and 3mm respectively for a traverse of over 1km. So it's as much real world value as actually having a 1" instrument after the fact. Which is of little value for live work like stakeout, though I could handle that too if I absolutely knew where I was going to be set up beforehand.
