Survey Quality Control???

[jimwaa]

I've been asked to develop a quality control system for the survey of a construction site. Is there any method or publications that are being used for Survey QA/QC?

 

[unioncarpenter]

Is it too late to comment on this thread?

 

[jimwaa]

No, its not too late. Please comment away.

 

[tsgrue]

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First, I suggest you speak with a land surveyor licensed in the project area about this matter. This may fall under “practice of land surveying” laws in the project area. It might require certification by an engineer or land surveyor licensed in the project area. If the project is critical enough to require a QA/QC plan for construction surveying, then input from am engineer or land surveyor experienced with this would seem to be well worth it.

I suggest you review the following US Army Corps of Engineers manuals:

EM 1110-1-1002 CECW-EP Survey Markers and Monumentations
EM 1110-1-1003 CECW-EE NAVSTAR Global Positioning System Surveying
EM 1110-1-1004 CECW-EE Geodetic and Control Surveying
EM 1110-1-1005 CECW-CE Engineering and Design: Control and Topographic Surveying

These can be download from: "

http://www.usace.army.mil/publications/eng-manuals/em.htm".

I also suggest contacting the National Geodetic Survey (NGS,

http://www.ngs.noaa.gov)

and Federal Highway Administration (FHWA,

http://www.fhwa.dot.gov)

for assistance. The US Army Corps of Engineers Topographic Engineering Center and your State Department of Transportation may also be able to provide assistance. I think the USEPA has guidance on this for landfill construction and TVA, USBR, and/or USACE have guidance on this for dam construction.

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tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

http://hhwq.blogspot.com

 

[unioncarpenter]

I was control for my last project, which was 150' deep, and 350' wide. The project involved approximately 100 columns, and 40 - 50 corners. Very few of the columns were in line, so setting hubs, batters boards, pulling strings and dropping a bob were out of the question. We bifurcated the job lengthwise, and established control points at each side to cut any error in half. If I could get a precise pk or scribe in concrete, I would drop down into the site to be closer to the action. My work was checked by an independent surveyor and found to be +/- 1/8".


If I were to start over, I would first, have the instrument calibrated, then set numerous control points in places which will remain undisturbed for back-sights, and establish some angle back-sight checks if you have some immobile structures nearby. A preponderance of places to check your setup is crucial. I had the advantage of having a second instrument available which I could set up and double check my working instrument occasionally.


I was involved in another project in which there was a question as to the precision of the layout work midpoint in the job, two survey crews were called in, and in the end, all three were different. I am completely self-taught, so I defer to tsgrue for what would be a proper, and most importantly legal, QC system.

 

[msucog]

from my construction experience, i was a field engineer on some large projects. prior to anything, i had every instrument calibrated (during construction, only a very select handfull of people could even touch the instruments). we had the PLS come in and stake out a half-dozen control points in different parts of the site. from there, i started my layout by checking their points, elevations etc (they do make mistakes occassionally too), and then stake my own control points around (also hid a handfull of points away from the work areas). for elevations, i establish the jobsite elevation and set my primary elevation pin in an area that will have no fill placed anywhere around it.

for each and every footing, i input all those points in to my data collector. i also input critical column line intersections as well as any control points. the very first pour, we made sure to pour footings on both ends of the buildings. the next morning, i would double check all the footings that were poured and scribed my control points at the anchor bolts as well as 1-2' offsets (can't see the scribes one the column is in place & used 1-2' offset so that i could still see the line once the slab is pour around the column blockouts). once my control is started and checked in initially, it does not change. accumulated error is hard enough to keep in check on very large sites much less if you change your reference or have other crews come in and cause even minor adjustments or errors. build everything relative to my initial control. my superintendent insisted on batter boards so we argued and cussed each other and i finally put something that looked like batter boards out on the site (by the end of the first week, every one of them had be hit and were out--duh! i would never trust a batter board except for "in the ballpark" measurements).

as contruction goes forward, follow basic surveying rules: check, double check, double check your double checks, check every measurement on the plans and tie them back in to the other measurements, have multiple backup points (don't paint them orange--that'll surely cause someone to hit them), and confirm multiple backshots everytime you set up. be picky about measurements. don't overwhelm yourself with 47 control points because you'll soon be pulling your hair out as soon as something doesn't check in. set you about 1/2 dozen control points in each major area and always use those points. as soon as one does not check in, i either figure out what the problem is and correct my setup/measurements or don't use it all. it's ideal if you can set all your control points on the front end of the job. if they're right at the beginning, it should be easy enough to be right at the end.

as soon as walls and slabs are poured, set 2' offsets for the column lines and set your 4' above finished floor marks. be careful with long walls (use multiple setups to mark your points or you'll end up with a vertically curved lines--and it doesn't have to be as long as you'd think before you start messing up since it's usually tied more to the optics than curvature/refraction error). again, follow good, basic old-school surveying tactics.

and last and most importantly, hire a good field engineer/surveyor. they're worth their weight in gold. hell, i took a 20% pay cut to be a geotechnical engineer...go figure.