I have heard that most (all?) bar code level rods come from Nedo, irregardless of whether it is for a Trimble, Leica, etc. And they are not interchangeable.?ÿ
I have a 4 m bar code wooden rod (four sections) for a Dini12 that I bought when it was still Zeiss (probably bought in the early 2000's). The rod does not say where it was manufactured. I also have three 3 m invar rods, and they all say made in Germany.?ÿ
So my old 4 m rod has been very good, and agrees well with the invar rods. The bar code is starting to become scratched off in places, particularly right about where we usually read it (around 2 m). So I bought a new one.?ÿ
First of all, the joints/clamps are not the same quality as the old rod. And the leveling results were not good, so I stopped using it. But the old rod is getting worse, so I compared each section (0 to 1 m, 1 m to 2 m, 2 m to 3 m, and 3 m to 4 m) of the new and old rods to the invar rod. And then I ran between my pedestals, which are 140 meters apart with an elevation difference of 15.7 meters. Balanced shots, stable turns. I got a difference of 13 mm between the run with the invar (loop closure +0.0002 m) versus the run with the new wooden rod (loop closure -0.0003 m). So I computed corrections for each section of the new wooden rod, and applied them to each sighting. The corrections for the old rod are in parenthesis
0 to 1 (zero offset): +0.0005 m (+0.0002 m)
1 to 2: -0.0012 m (-0.0006 m)
2 to 3: -0.0017 m (-0.0003 m)
3 to 4: -0.0027 m (-0.0014 m)
Once I applied the corrections, the agreement was much better, 0.003 meters.?ÿ
I wonder if the Nedo wooden bar code rods are now made in China? I can definitely see the difference in quality and the calibration results of the old versus new rods.?ÿ
One interesting thing I found from this recent survey is that we had previously run between the pedestals in 2015 using the same invar rod. The difference was 21.5 mm, and I had always assumed that these two pedestals (4' in the ground, 3' above ground, filled with concrete) were stable. In 2015 we also ran to two nearby high voltage electric monopoles with massive concrete foundations. They prove that the upper pedestal is stable at the less than mm level, while the lower one (possibly on old fill) is the one that moved.?ÿ
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Another thing I always wanted to find out but even the distributor could not answer. Do you need to calibrate the rods? My bar code staffs are 3-part detachable. I rarely use the 2nd/3rd legs because most runs are on relatively low variation routes. I have often wondered if the part where the legs interconnect would cause any variation in the readings? Since we are talking of getting accuracy on the 0.003m/loop then it means the interconnection would be the weakest link in the whole system.
For: John Hamilton, your post above leaves a lot of questions. But first if you read the Specifications for Electronic Digital/Bar-Code leveling
you will see that for 1st, second and 3rd order leveling that the rods must be one piece. So you are trying to compare a 4 meter 4 section rod
with a one piece 3 meter rod ( which as you say did agree close at one time,?ÿLUCK). If you use a rod that snaps together then you must be
doing less than 3rd order work (by the FGCS specifications).
Questions.?ÿ When you use the DiNi 12 to you have curvature & refraction?ÿ?ÿON or OFF ??ÿDo you let the instrument adjust to ambient temperature?
Do you use a 30 meter?ÿmax sighting distance (recommended for digital/bar-code levels)? Do you use a umbrella to protect the inst.?
You make a statement; "difference in quality and the?ÿcalibration results of the old versus new rods" You are not calibrating anything you?ÿ
are?ÿcomparing.?ÿIf you want to calibrate the rods (bar code) then you must turn the rods and instrument into a National Lab.
Last comment, you talk about your pedestals?ÿ and you assumed?ÿthey were stable; 4 foot in the ground, 3 foot above. Well I guess you
will not assume anymore(?) Question: what was the diameter of your pedestal?
?ÿ
JOHN NOLTON
@jt50 Your question "Do you need to calibrate the rods" answer NO.
Since you are using a 3-part rod and that is not allowed by the FGCS spects. to do 3rd order or above leveling you only need the
Manufacturer's standard.
JOHN NOLTON
I am not interested in running 1st or 3rd order following FGCS standards. What I am asking is, how will the connecting part of the rods affect the stated accuracy of digital levels in day to day level runs. Most digital levels using standard fiberglass interconnected rods have published accuracies of 1.5mm/km double run which falls above 3rd order precision. They never address how the interlocking rods will affect accuracy.
@jt50 I think you must read your post again. I answered your very FIRST Question. See your first line above. I forgot to answer
your 2nd question; " I have often wondered if the part where the legs interconnect would cause any variation in the readings";
that's in your 2nd and 3rd line above. Its sometime referred to as Junction error. Your answer is YES.
JOHN NOLTON
Sometimes if you don't know the answer it's also ok to say I don't know the answer to your question and just shut up than to bring up terms like Junction Error that really does not contribute to the discussion.
@jt50 John Nolton knows more correct answers than you'll ever have questions for.
Maybe you need to learn how to ask questions.
The question was not directed towards him in the first place. He interjected about FGCS standards which was NOT in my question. Maybe he needs to learn to read and answer the question directly. What's the use of knowing the answers if he can't even share those on such a simple question?
Not every discussion needs to be a graduate school thesis defense.
As I stated, I have three 3 m invar rods, two of which were calibrated at SLAC and the other is manufacturer calibration (the latter is OK for 2-II). I also have two 2 m invar rods.
Yes, the joints are the problem. I used to use a Leica digital level in the early 90's, those rods were very bad over time, the joints would get loose. I made it a point to buy a new rod every year. The Zeiss/Trimble seems to be a better design, the 4 piece rod has remained very stable over time. But it seems the new 4 piece is not as stable, hence the reason I ask if they changed manufacturing locations.
And when I say I calibrated the 4 piece rod, it is not a formal calibration, it was simply to get a measure of the discontinuity at the joints. I modified my processing program that reads the digital file and outputs a field book format to apply the corrections in the processing.
pedestal...one is 12" diameter (the stable one), the other is 6" diameter
Yes, the joints are definitely an issue. I can remember in the old days before digital levels when using a philadelphia rod, they were adjustable at the joints. But, the only way we had to adjust them was using a steel tape, and we could get them probably ?ñ1 mm (0.003'), but not really any better. The new digital rods are not adjustable at the joints. That is the reason I compared them against a one piece invar and computed corrections to be applied to each section.?ÿ
Last year I purchased a lighted one piece rod (not invar). I was very disappointed with the accuracy (compared to a one piece invar), and returned it. I didn't expect it to be as accurate as invar, but it was significantly off. I contacted the manufacturer, they said it was "within spec".
In my area (western PA and West Virginia), there is a lot of relief, and you can pick up significant error when going up and down hills. If you run up a large hill using a folding rod, and then back down, there will be usually the same amount of high rod/low rod shots, and the errors will cancel out and give a very good loop closure. But the elevation at the top can be significantly off, I have seen errors in the 10 to 20 cm range on long uphill runs. Those situations are important to have the invar equipment.?ÿ
I do not see many people out running levels with invar. So I believe this is an issue that many are not aware of. Or don't care about.?ÿ
We run a lot of high accuracy leveling for deformation surveys, that is why we have the 5 invar rods I mentioned, plus a 0.5 m invar strip that is used for vertical set marks. However, many of the earth dams we monitor have pins inside an outer pipe, and the invar will not fit inside the pipe, so we use the folding rods. But, the accuracy requirement is less for earth dams compared to concrete structures, and they are very flat, so the pins are all at the same elevation and the issue of the joints does not enter in.?ÿ
I think we tried to use 2 legs in one of our level run on hilly roads. The safety engineer advised us not to use it because it may touch some low electrical wires located along the sides of the road. You are correct that errors made on the 1st run may be cancelled out by the return run so you may think that everything is calibrated. For critical level work, we are required to make a 3rd run on a different day & time and see if this agrees with the previous loop. If outside of the required precision then we need to rerun the 3 lines.
While I?ÿ cannot say with certainty where the Trimble rods are manufactured, the packaging definitely says "DE Germany."?ÿ That could be where they are manufactured, but it could also only be where they are boxed up for distribution.?ÿ
