Activity Feed › Discussion Forums › Strictly Surveying › Traverse network – leveling instrument after change of station
Traverse network – leveling instrument after change of station
rplumb314 replied 2 years, 9 months ago 18 Members · 33 Replies
Being pedantic, you can’t “calibrate” a tribrach, all you can do is “adust” it.
For precise work I always carry a separate traverse baseplate which has a plate bubble. This is used to exactly level each tribrach when it is centred on first setting up. Ignore the tribrach bullseye bubble, but if that is out then mark the tribrach to be adjusted when you get back to the office (because the plate bubble can be rotated through the quadrants you know that the tribrach is truly level). When the instrument goes on it should only need a tweak on the footscrews to be level. If it, or the backsight target needs more than a touch on the foorscrews then you know the legs have settled or the tripod has been knocked.
@john-hamilton Star*Net Pre-Analysis and figuring out what Degrees of Freedom you need to achieve your desired standard error is a beautiful thing that I just got a grasp of as we had to achieve 3mm at 95% on our Dam Deformation tri-lateration surveys for the USACE. I thought there was no way it could be done when I had shots as long as 17,950′. It came up to be 6 DOF per point from 3 different control monument towers. (18) measurements per point total.
If we are being pendantic…
????
https://www.merriam-webster.com/dictionary/calibrate
cal?ú??i?ú??brate | ??ka-l?-??brtcalibrated; calibratingDefinition of calibrate
1: to ascertain the caliber of (something)2: to determine, rectify, or mark the graduations of (something, such as a thermometer tube)3: to standardize (something, such as a measuring instrument) by determining the deviation from a standard so as to ascertain the proper correction factors4: to adjust precisely for a particular function5: to measure precisely (especially : to measure against a standard)-All thoughts my own, except my typos and when I am wrong.To be fair, we might say that the calibration of “calibrate” has been calibrated differently over the years…
But that would be a stretch (perhaps another calibration?) of the word.
-All thoughts my own, except my typos and when I am wrong.pendantic?
I’m with Mr. Mills on this. “Calibrate” may be technically correct but in this context “adjust” is a better word to use.
@norman-oklahoma
Item 3 in the definition is probably the one to use in survey, where we determine the corrections to be applied on a blanket basis to the readings taken with a particular instrument/accessory combination.
For a level, you can only check and adjust. You can’t easily have a correction value to apply to the readings (yes, that can be done – I’ve had to do it when observing into tunnel kilns while they are still hot, where the refraction due to the heat gradient is large, but I don’t recommend it as a career!)
For an EDM you can calibrate as well, so as to have a method of correcting the distances – subject to it being used with the SAME prism. You can, of course, also check each individual prism so that you also have a calibration constant for those.
The critical thing with a “calibration” is that the operating set-up is with the same accessories as the calibration (or using the same reflective surface if on a non-contact instrument (try yours on a dark blue card, a white card and a red card).
“Calibrate” implies that you are making the device perform the same as some other other device – equalizing individual units. “Adjust” implies making the device conform to some natural physical property, ie/gravity.
@norman-oklahoma
Correct, and neatly put.
@norman-oklahoma
Question: What does the Thesaurus eat for breakfast?
Answer: A synonym roll.
Historic Boundaries and Conservation EffortsWhat is another word for Thesaurus?
This is how I do it, as soon as I set up I shoot foresight so that the stations are at there most accurate over the point, measure intermediates and switch stations, if the compensation is of 30 seconds out when set up on the next station I analyze the accuracy needed but most of the times I would relevel and re-center if over 30 seconds. Keeps everything tight, no worries, if its under 30 seconds when your put the jigger on the next station then play on son!
Also to eliminate taping height error’s I always shoot an intermediate point that I can see from next station and transfer/ height from that point, or at least check that your getting similar heights from next station, this keeps everything consistent through you’re traverse and gives you a nice little closing height error.
I have never used a TS16 and know nothing about them. But 20″ or 30″ of angular error is a lot.
I just downloaded a user manual for the instrument. Three out of four models of TS16 have an automatic target aiming function. For the instruments with that function, it evidently doesn’t work properly if the compensator is turned off. The manual says (page 55):
“If the compensator and the horizontal corrections are activated in the instrument configuration, every angle measured in the daily work is corrected automatically. Check whether the tilt correction and the horizontal correction are turned on.”
It also says:
“The results are displayed as errors but used with the opposite sign as corrections when applied to measurements.”
This sounds as though the instrument might display something like +20″, meaning there is an error in that amount, and that the 20″ should be subtracted from the measured angle. Again, I have never used this instrument, so I don’t know for sure what that means.
Perhaps someone who is more familiar with the TS16 will be able to explain this better.
Log in to reply.