Options for surveying large concrete structures?

[StructureMan44]

On an outdoor 100ft long concrete foundation supporting large machinery, what options are available to determine variation in the top surface in addition to traditional surveying (total station, pole, etc.)? I have a structure that was built about 6 years ago that recently has started to form puddles on the top surface after rainstorms. I’d like to determine the variation in the top surface and measure it periodically to determine if it’s getting worse (possible excessive creep).

 

[Canuck67]

No direct experience with it, however, testing and inspection companies are usually setup to measure floor flatness (F-numbers), which would not provide elevations, but would provide relative measurements. I believe it works from a set of long straight edges and measurements are taken in a circular fashion. If benchmark locations were identified, they could be re-measured at intervals.

 

[jgailla]

http://www.ribmc2.com/estref/popular_conversion_files/concrete/slab_flat.html

Most construction materials testing/geotech engineering companies should be able to do these.
I've only seen it used on slabs and I don't think it's applicable to your issue.
If it's a strip footing couldn't you just set a benchmark and get a vertical point every 5 feet or so?
If you're worried about differential settlement you may not even need a permanent benchmark.

 

[Brad805]

You could rent a 3D laser scanner or hire someone to do it. We have rented them. They are becoming more popular.

 

[oldestguy]

Don't use a construction laser "level" . The accuracy usually is too crude for what you need. What's wrong with a traditional transit-level? Remember they can be off also, if not in adjustment. Verify that with the two peg method. Of course you know what I mean? Right?

 

[CarlB]

You could use a digital manometer, such as this one

http://prolevel.com/

I've seen some literature that says they are accurate & repeatble to 1/8" or less.
If floor area is congested, may be simpler to use this than surveys relying on line of sight.
You'd want a datum point in the building that isn't moving, as a reference for successive surveys.

 

[cvg]

lidar scan is quick and easy
a 10 foot straight edge might also be useful, they are commonly used for checking pavement flatness

 

[StructureMan44]

Thank you all for the feedback. I'm making a list of the available options and researching which make the most sense for this situation. Is LIDAR the same as 3D laser scanning?