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Setting Good Control For Large Building Layout
dmyhill replied 2 years, 8 months ago 18 Members · 47 Replies
- Posted by: @chris-bouffard
There is nothing more humiliating to a PLS than calling the contractor and telling them not to use the stakes your crew set because they are wrong.
Not for this PLS. It’s no fun to have to make that call, but it’s far more humiliating to be backcharged thousands of dollars because we didn’t do our due diligence and catch an improper calculation or cut/fill during the QC process. Errors in setup are rare, even with crews regularly resecting; it’s usually a bad office calc, or an incorrect field calc, a cut/fill in the wrong direction, or a planset discrepancy, etc.
My first party chief and mentor once told me, “a stake in the wrong place is not a mistake until something is built off of it.”
The good contractors understand that occasionally things go sideways on a stakeout, and would much prefer that a surveyor correct stake locations rather than having to rip out improvements and re-do them. The former may cost them anywhere from nothing to a few days, while the cost of the latter starts at weeks and can stretch to months. Not to mention the paperwork and bad blood that inevitably follows.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman @chris-bouffard I have to resect all the time on large sites simply due to the large amount of equipment, spoil piles, building materials, etc. in the way. I always use three points and then verify to at least two more post resection.
True story from back in the day when caller ID didn’t exist and I was nicer to unsolicited phone callers —
<phone rings>
Me: Hello.
Jackass: Hi, I’m calling to <offer something I can always live without>.
Me: No, thank you. Have a nice day. <hangs up phone>
<phone rings again>
Jackass: Hey, you cut me off!
Me: Why, yes I did. <hangs up phone again>
Jeff D.You can get in with most of the contractors, and everything’s going great, but as soon as the iron workers come in, the whole thing goes sideways. Bunch of cowboys, thinking they’re the rock stars of the show
I’ll allow that it is prudent to ensure that your crew has attained a certain level of general competence before attempting them, and that the supervising PLS establish clear procedures to be followed.
A few monitor projects one year, using StarNet and the internal calcs from the DC, I ran both resections and traverse to establish control for each point we monitored. (Meaning we established new control each day, often on the same marks, but reestablished that day from control outside of the zone of disturbance.)
Resections are better…100% better.
Other evidence? We used to run control on the curbs in subdivisions to set the mons, and balance the results in StarNet. The best practice was to place a couple of points in the middle of the subdivision that were observable from many other points. Simply shooting them in and creating that network created a night and day difference in the end product. You could run the traverses different ways and see the differences.
I am completely convinced that resections from points outside the zone of disturbance are the correct way to establish working control points. Is it possible (even easy) to get it wrong and mess it up? Yes. Build in checks. Can you get lazy and use just two points that have bad geometry? Yep. But, assuming the same level of care, resections are safer, more accurate, and more precise, in my experience.
-All thoughts my own, except my typos and when I am wrong.
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