@dmyhill - agree there completely. I see way too many these days who just trust the automatics of GPS for fine grading streets or other subgrade crucial surfaces with newer dozers outfit with automatics that are advertised as being capable of such. Then the paving crew shows up to complain about the uneven grade rocking the paver's screed or somebody will say the pavement thickness in the asphalt reports wasn't to spec when in my opinion it wasn't an issue with the paver's screed adjustment while moving but rather relying on the wrong equipment for the job - so use the motorgrader and free-hand it the last tenth or so! those crusty old timers did it for eons while walking to work uphill both ways in the rain so you can too ????ÿ
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Plus GPS/DTM model builders don't usually think like a grade foreman does or how the guy running the paver will make his pulls while moving down a street, at an intersection or through a parking lot's short run of spaces. Some smaller contractors in parking lots are ok with the GPS/DTM model getting them close enough on the stone subgrade elevation then they'll pull string line from lip of curb to lip of curb and have somebody check subgrade depth with a folding tape. But if you did that and the parking lot was supposed to have an inverted low for a paved swale through it?ÿ that is vertically lower to say an drop inlet then would the string line method actually work from curb to curb? no probably not. But did the GPS/DTM model even reflect that intent if the engineer's proposed contours didn't show that inversion? my money is on Murphy's law and the "CAD guru model builder" never having actually pulled string lines through parking lots, busted out a carpenter's level to check fall, setup lasers for slopes or shot grade for days on end when the grades don't work out haha - I'll try to stop now as I don't want to hijack a good thread on something else