I distinctly remember the answer to a question that my professor asked one day in grad school. Too bad I don’t remember the question. It was somewhere along the lines of “Why should we accept this result?” Several students tried to answer the question with an analytical or calculated result. But no one got it right. The answer, according to the professor was “Because it’s good enough.” His point was that we may never find the true answer, but the answer we got is close enough.
I am reminded of this a lot in our work. We deal with software that calculates at a ridiculous precision level – something like 16 decimal places. Yet we deal with disciplines like surveying and civil engineering, where sometimes ½ of an inch is an acceptable tolerance. We often assist a construction surveyor and I can’t help but laugh sometimes at the level of precision he is okay with (see ½ of an inch above), especially when the civil engineers that created the plans were probably fretting over a lost 1/100 of a foot somewhere.
To me, this is one of the things that separates an inexperienced surveyor or civil engineer from an experienced one – understanding when the answer or result is “good enough.”
Civil 3D helps a little with putting precision in perspective; because you really can’t cheat or fudge with the software. The labels are a result of the design. The invert elevations shown at a sanitary sewer structure are a direct result of the pipe slopes, lengths and starting elevations that you entered. If that invert elevation is off by 1/100 of a foot from your design, with previous software you might recalculate everything by hand (If it’s off by 1/100 of a foot, maybe it’s really hiding a egregious error! Engineers are a paranoid sort). But in Civil 3D, you know the pipe slopes that you entered are solid, you know that the manhole locations are solid, and you know that the starting elevation is solid. If that invert looks off by 1/100 of a foot, it’s probably a rounding error. Let it go. It’s good enough!