I'll go on record, no one is really getting that kind of accuracy, and for almost all projects, it really isn't needed.
Storm sewer, sanitary sewer, culvert??ÿ Might as well record to the hundredth--the next best option is a tenth.
In some sewer projects I've done as well as concrete slabs/gutters, showing inverts to a tenth would jeopardize passing inspection (not to mention flow). 1/2% for 25' is 0.125 (0.13) but rounding that to a tenth blows it.
With the rod tilted, and sometimes guessing what you're resting on, broken pipe, covered with crap, etc, it's tough to pretend to get that kind of accuracy.?ÿ
I've seen guys spending time, trying to compensate for tilt, and record numbers that show flow running opposite from reality, and you can clearly see that one pipe is lower than the other, but their notes say otherwise.?ÿ Oh, well
In the grand scheme of things; if you think all of your measurements are within a hundredth, you're kidding yourself...
If you're using the right tools, to get inverts, you will get pretty close.
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It said "recorded to" not "guaranteed accurate to".
Looser than hundredth would not have to be tenth. It could say 0.02 or 0.05 or other I crement.
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It always amazes me how they calculate the slope of a pipe run between manholes with only two pieces of data, disregarding the 200 to 300 feet in between. Theoretically that may be fine for a design.
The only way to "as-built" a pipe run is to make measurements as it is built. Making observations at the top of the pipe, and subtracting the thickness and diameter will give you the invert, alignment, and actual proof of how the pipe was constructed.
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Historic boundaries and conservation efforts.
Any of you old farts remember Lamping and/or Mooning a sewer line installation? ?????ÿ
It said "recorded to" not "guaranteed accurate to".
Looser than hundredth would not have to be tenth. It could say 0.02 or 0.05 or other I crement.
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Well yeah, no kidding.?ÿ You get the pedantic point award.
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Makes just as much sense as reporting a property boundary to the 0.01' (which is none).
This is one of the fallacies promoted by our profession.?ÿ We consistently claim to be perfect measurers as that is what most clients believe us to be.?ÿ They don't understand all the mumbo jumbo speak we use and translate that involves title, physical evidence, parol evidence, perpetuation, and a host of other terms they assume attorneys are the only ones that understand.
The flattest sewer and storm I??ve commonly staked is in the most mountainous state I??ve lived in. If you are surveying for design err on the side of low on the outlet and high on the inlet. Better they design it a little bit to flat than a little bit to steep. ?ÿEvery measurement has error. ?ÿYou??ll still get your full moon. A good construction surveyor is going to verify both.
Looser than hundredth would not have to be tenth. It could say 0.02 or 0.05 or other increment.
I record to the nearest 0.01', but I annotate to the nearest 0.05'.?ÿ Even with the Chrisnik Pipe Mic (which I only use if I'm opening a bunch of MHs), I don't think I get any better than 0.05' accuracy.?ÿ The leg flexes a bit, and plumbing the rod bubble while reading the rod (manhole hook laid across the rim) introduces additional error.?ÿ But in 40+ years of dipping manholes, I have yet to have an engineer complain that my inverts aren't accurate enough.
The only way to "as-built" a pipe run is to make measurements as it is built. Making observations at the top of the pipe, and subtracting the thickness and diameter will give you the invert, alignment, and actual proof of how the pipe was constructed.
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Oh no!
All that tells you is the "as-laid" situation. Trench was then backfilled and construction traffic probably ran over it.
In any case, as others have said - read to 0.01' but state quoted values only accurate to 0.05'
where I live curb is frequentyly laid at 0.5%, street's strip-paved with side ditches at 0.3% and larger 48" & 54" RCP sewer outfalls are laid on ridiculously flat slopes so that you can run them for miles and miles along a stream or creek's watershed before a lift station is needed - just has to be done that way but it works. Even a recent smaller outfall of 24" was laid at 0.15% at times in order to maintain adequate vertical separation where needed or be deep enough to run that sewer to an area further up the reach and lower than what's in between potentially. Throughout my limited career I've always heard other engineers (typically at firms that performed the engineering & project's surveying) want to refer to these plans as record documents rather than as-built plans. Essentially it's a record of what that particular survey crew shot that particular day. They some times better understand that no two surveyors are gonna agree exactly on everything and I have seen it too where some streets' utilities or subgrade were not properly bedded or compacted which later on led to settlement. Some may get upset at this and say it's lack of diligence or improper procedures in surveying but it's the truth if the field crew happens to shoot something good on one particular day only to come back years later and note the same vertical isn't holding true anymore due to changing site conditions and circumstances. Some times it was best to put a record document note stating such and noting the day that the surveying was performed.
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as the project engineer before, I have seen 4 different 3man crews all from the same firm's survey department go out to "as-built" shoot the inverts on dual 72" RCP in large precast storm manholes close to 8' interior diameter that were close to 23' deep (large industrial project close to 80 acres). On certain instances, the field book's level notes by the different party chiefs agreed within 0.02' on the same inverts and at other times as much 0.18' out. This required one man down at the invert holding a 4' or 6' masonry level in the invert of the pipe where the other end had a piece of flat bar stock screwed to the tip so that the grade rod could be supported by it at the same elevation. Man up top at the grate or MH rim would do his best to level up the grade rod while the part chief was booking rod readings. I had doubts to the contractor that did the work as they bid it much cheaper than any of the local outfits and laid it much faster. But hey - the GC got exactly who they wanted at the price they wanted. Being that I wasn't comfortable with the results nor the work of said contractor I left the record documents up to the firm owner to decide on. But the project got it's map recorded and the CO awarded and it's functioned just fine for several years now
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While some might say this is sloppy surveying with that sort of variation, I'd gladly ask how close do you often agree with another surveyor's wide open & easy boundary survey - given changing sites and some times just flat out lack of agreement? Much less the task of shooting inverts over 20' deep with it requiring 3 people at times and being confident in your results? Do you have it in the budget to shoot said inverts multiple times on projects such as these? Most don't I'd wager.
While I agree on any inverts on an as-built being actually accurate to 0.01'?ÿ You can use a hidden point routine in SurvCE or record the data and use a spreadsheet. I think this is much better than sloping poles and other +/- methods.?ÿ
That's a handy routine, it's rarely used in my experience. Trimble Access has it embedded as an observation type.