GPM3 Parallel Plate Micrometer - Price: around $1,700.00
Leica NA2 Level - Price around $5,000.00, includes invar rod.
There are terrestrial (not aerial) photogrammetric techniques to that problem, and to that accuracy. However, that is with reference to something in the near distance that is not likely to have any movement. Not too difficult to do if you are interested in monitoring hundreds (or thousands) of points. For a few dozen points, it's not an appropriate technology.
have had 3 monitoring projects and on all three I used the robot. In each case hole punched from reflective target material where used. With a cordless Makita hammer drill stainless steel 5mm where drilled than glued into the railway concrete bridge piers. The piers where then pressure grouted to reinforce the foundation and in the other site the pile driving was for a new parallel rail bridge. The new piles where 120 long and never reached refusal.
The reflective dots where glued on the end of the stainless studs. The robot was positioned to shoot
The center of the reflective dots and this gives a 3D position for movement unlike digital levels.
The parallel new bridge work caused the old bridge to tilt 10 mm not a big deal the cross surface elevation was fixed with tamper and some shimming.
Monitoring is about targets and observing them so I would say little have moved except for
Target “A” N + 0.002
E - 0.003
Z - 0.004
Target “B” so on
Target “F” so on
Run a nice 1mm xyz traverse on stabile points and shoot the dots you will need a 1mm 1 sec robot
Peter K
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"Do a search for inclinometers...."
I believe you meant extensometer
Mike,
I think he may actually have meant inclinometers.
We have a "monitoring specialist" consultant who uses inclinometers and tilt meters (and liquid levels). "Apparently" they can detect 0.001" (or thereabouts) of movement if set, calibrated and maintained correctly.
(Is there an emoticon that rolls his eyes?)
The buggers are expensive to buy, maintain, and analyze properly.
And their application is limited; I wouldn't place one in an active de/construction site.
The extensometer might be useful, but it's range to a stable reference is limited to it's tape length. They are excellent in tunnel "out of round" surveys, where you only require the relative change in diameter and not absolute directional dimensional change.
In any case, not knowing more about the scenario posted here, no reccomendation is entirely appropriate.
P.S. I will be using your "zeroes" quote in the future. Nice one.
I experimented with using linear variable differential transformers (LVDTs) as extensometers, in a situation where we needed continuous digital monitoring and recording of structural displacement. I mounted three of them in mutually orthogonal orientations to monitor in 3D.
We were able to continuously monitor long-term changes between two adjacent building slabs, in a radiation environment, with a meaningful precision of 5-10 microns (about the width of a blood cell).
The limiting factor for precision appears to be the fluctuations in air temperature in the air-conditioned room in which the signal amplifiers are currently located.
- Doug
Scott
Pure straight settlement would be a an extensometer. Try googling a multiple position borehole extensometer.
An inclinometer is for slope relative to gravity.
Mike
Ahhh...
I was speaking from my experience.
I wasn't aware of the type of extensometers you mention.
Just the ones I've used.
Just proves you can, actually, learn something new.
This link may offer you some ideas, although from a quick review, it doesn't appear that they were shooting for that 0.001 number:
http://www.wmata.com/pdfs/business/ACPM_Rev4_02-16-10_FINAL.pdf
