The ways of the screwup are many, and varied. Suffice to say that I've seen plenty in simple traversing, too.?ÿ
I always use at least 3 points in my resections, retain the data, record check shots, etc. etc. Sometimes the results of a resection are not great, it is true. But the statistics that my dc returns on a resection actually give me more information about coordinate quality than I get by other means, not less, so I know it on the spot. I'm using at least 3 controls, all of which have to be correct, not just 1 and a BS.?ÿ I'd be very confident going into whatever court I might need to with my resectioning data.?ÿ ?ÿ ?ÿ?ÿ
imagine something going wrong with a resection, causing something to be built incorrectly.?ÿ When you are sued and explain the standard of care that you employed as being based off a resection, how do you think that will fly?
You say that as if a resection is somehow inherently "less than" a typical single-backsight setup. I would be very interested if someone - anyone - on this board can tell me exactly how a properly performed resection is less defensible than a single-backsight setup.
We employ resections, keep all our raw data and field notes, check our work in the office, and don't lose any sleep at night. I've had to prove out stake points from resected setups multiple times. Across five employers in sixteen years I can't ever recall an instance where someone attempted to backcharge us or take legal action based upon our choice of setup. It's our responsibility to choose procedures that enable us to place stakes correctly. If they turn out to be wrong, no one cares why they're wrong, and I would never argue that my choice of setup might relieve me of that responsibility.
I've personally only seen bad results when it was clearly not going to work well...I was just using it to find a control point. Like shooting 2 points no where near 90 degrees apart and staking out a control point a ways away from me just to get close enough to find it with the metal detector. I always tried to make a habit of seeing how far off it was before moving the robot to it.?ÿ
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@rover83 Just like anything else, the software is only as good as the people using it.?ÿ If you don't understand what you are seeing it falls back to the age old statement, garbage in, garbage out!
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@norman-oklahoma but you have the time in to understand the math behind it and enough knowledge to accept or reject.?ÿ You have the time and experience in to know when something just looks or smells wrong.?ÿ That's a different ball game compared to what companies are doing now, out of need to keep the work flow going they are making newbees PCs in a matter of a year or two.
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@rover83 "Properly performed".?ÿ I'm 38 years in and have so many horror stories from 6 different places that I have worked.?ÿ I have had to put the emergency breaks on far more than once and sound the alarm because a short cut that somebody tried to save their efforts in the field went south.?ÿ 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.
@350rocketmike that's a valid use if you are not staking critical construction points.
But that really doesn't make a difference whether or not it was a resection they screwed up right??ÿ
I know of an instance where a crew at our other office occupied the wrong point and backsighted, got less than 1cm error and didn't do a check. There were 2 points both basically the same distance from the backsight and they assumed they were good and laid stuff out like a meter off.?ÿ
I'll never do any layout or tie in anything without a check, either way. But if you're saying no resections because you don't trust your guys to do them right....you must also have specific instructions for them about how to backsight and check as far as good geometry goes?
As to a standard of care, it is a question of not being negligent.?ÿ?ÿDid your equipment, methods, and procedures fit the work at hand??ÿ I can do the math to calculate the errors in my measurements.?ÿ With a resection I can see the residuals of my calculation.?ÿ I do not believe that I would have a problem explaining a resection, I am making redundant observations to multiple control points.?ÿ I have also used StarNet to adjust my control network using appropriate errors and weighting.?ÿ This will again yield a report with error ellipses and testing results.?ÿ Is radial stakeout an inappropriate method to layout a building, no. ?ÿIs that how I would layout an entire building, no.?ÿ Can things go wrong, sure.?ÿ Did things go wrong when the tools were a 20? transit and a steel tape, yes.?ÿ Like it was said you can never have enough control, additionally you can never enough checks.?ÿ It is about being competent and knowing your work.?ÿ
the ??resections only as a last resort? tells me you have been at this game for a while. I was also taught that, and it comes from old school resections determined from angular values only. Assuming the geometry is good (ie: not inline or acute angles) a 4 or 5 point resection is generally really good. Modern software packages can even isolate bad control points within the resection and recalculate your position, much like GPS calibration (localization) procedures.
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.
@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.
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True story from back in the day when caller ID didn't exist and I was nicer to unsolicited phone callers --
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<phone rings>
Me: Hello.
Jackass:?ÿ Hi, I'm calling to <offer something I can always live without>.
Me: No, thank you.?ÿ Have a nice day.?ÿ <hangs up phone>
<phone rings again>
Jackass:?ÿ Hey, you cut me off!
Me: Why, yes I did.?ÿ <hangs up phone again>
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.?ÿ Bunch of cowboys, thinking they're the rock stars of the show
