I am working on a project where we are installing 12m high 1.5m wide glass panels. The finished iron structure should be within 2-3 mm. I use a FG-L30 nadir and zenith plummet for final check. It works precisely, but slowly. Could you recommend a similarly accurate (+/-1mm/30m) plummet, but with compensator?
You have several choices. You will find some on ebay (zenith) or you can rent one from several places.
One such place would be SwissTec in Brewster, NY. phone 845-278-2335
The last time I checked he had both the wild ZNL or the NL and ZL ; something like $80 per week.
What type of total station do you have? You can purchase diagonal eyepiece and look at the zenith.
?ÿ
JOHN NOLTON
Old Shatterhand?ÿ?ÿin my post above its SwissTek not SwissTec
?ÿ
JOHN NOLTON
It works precisely, but slowly.
Most of the time. those 2 words need to go together.
@jt50 I was thinking exactly the same. No one makes a plummet that will work any "faster" than the one he's using, considering that they're basically all the same thing.
For:?ÿ ?ÿjt1950?ÿ and?ÿ Plumb Bill
The plummet that?ÿOld Shatterhand is using?ÿDOES NOT HAVE A COMPENSATOR IN IT. It uses a 20 second bubble per 2mm
standard Wild T2 bubble. If you have to move it on the tripod you must re-level (or at least check the level) It is slow.. As he ask
is there a instrument that will give him at least the same accuracy?ÿBUT WITH COMPENSATOR.
The Wild NL and the ZL both have a compensator. The FG-L100 (same manufacture as the cheaper FG-L30) but has a?ÿcompensator
in it but is only a?ÿZenith machine.?ÿ The FG-L30 is +or - 1 mm at 30 meters.?ÿ The FG-L100 is + or - 1 mm at 100 meters.
?ÿ
JOHN NOLTON
@john-nolton Thanks for the translation! That's exactly what I mean. I use Trimble 5602 and I've already bought 2 diagonal eyepiece. The first was threaded, could not be connected to the instrument. The second one was already good with a bayonet lock but I don't know where it is now. 😥 ?ÿ But I think the direct reflex is not suitable for mm accuracy.
@old-shatterhand I looked up the spect. on the Trimble 5602 and you are correct; it not accurate for your work.
Question: can you get (borrow) another theodolite that has compensator's that are accurate to less than 1 second of arc?
One of the old instrument, Kern E2 has dual compensator that are less than 1 second. There are other theodolite's that also have
them and you can use a diagonal eyepiece to look at the zenith.
If that won't work for you then you are back to renting or buying (from ebay or other place) a Wild ZNL or ZL or
other brand. You will have to do a search and find what is available in your area.
JOHN NOLTON
I'm not sure (shooting from the hip) but I don't think any total station would be quite what you want. Most mathematically apply tilt compensation - so unless you stake to the line at a certain elevation you could dial vertical on the scope but still not be correct along the entire path. Mechanical tilt still exists as projected through the crosshair. The Wild and Leica plummets you mention have a mechanical tilt compensation mechanism much like an autolevel, and project veritcal much more accurately via the crosshair.
I assume you already knew all that. What I meant by "won't be any faster" is because there is no instrumentation that can project vertical any better than a truly mechanically compensated purpose-built plummet. So there really is no faster way other than sighting through the unit. Unless the one his is currently using (I don't know much about those) requires several more setups and checks due to inherent error.
@plumb-bill It sounds like you have never read about or used an optical plummet. I would suggest you read
the following; 1. Surveying Instruments by Fritz Deumlich page 153-156
2. Surveying Instruments and their Operational Principles by L. Fialovszky page 365-373
3. ISO 17123-7 Optics and optical instruments--- Field procedures for testing geodetic and surveying instruments--
Part 7: Optical plumbing instruments.
After that go out to the field with both kind of OP (spirit-level) and compensator and test them both for hours.
After all that you can then test a total station with diagonal eyepiece and while your at it get a old style Wild T2
theodolite with a striding level and test both of them.
JOHN NOLTON
I have used a Wild ZNL several times for accurate setup.?ÿ Not to prolong plumb upwards, and for what we were doing it was overkill, anyway.?ÿ Hope I never have to.?ÿ I don't have those books.?ÿ I'll admit I was discussing based on assumptions from information that was relayed to me.?ÿ I was told they basically work the same as autolevels, but vertically.?ÿ If that's not the case then, whatever.?ÿ I don't use them often so I don't need to know.?ÿ Don't have T2.?ÿ Would like to have one for fun if nothing else.?ÿ I have used a modern total station extensively, and I know the Trimble VX and S6 in particular apply a mathematical solution to correcting tilt.?ÿ If you use the laser oriented vertically it will introduce error compared to taking an observation to a prism along the same vertical path.?ÿ That is what I was referring to.?ÿ Never held myself up to be an expert on all things plummet - just seems (from years of experience) to me if you're trying to be super precise/accurate slow and redundant is going to be the recipe no matter what equipment you use.?ÿ If his doesn't have a compensator it sounds like it might be intrisically more accurate in a purely mechanical sense than a total station utilizing a tile sensor.?ÿ Which belies the intent of my original post, indicating that it is just going to be a slow project.
My experience with optical plummets is almost exclusively limited to those in standard tribrachs, but I did have an opportunity to use the plummet that NGS provides for calibration base line measurement once.?ÿ It made the dimple in the mark look like an asteroid crater.