Drone mapping caught a grade error my crew missed for 3 weeks

We were backfilling a commercial pad in Austin. The laser level said we were dead on. But the water pooled in the exact same spot every rain. Three weeks of that. Finally rented a drone with RTK on a Friday afternoon. One flight showed the whole slab tilted 0.4% toward the corner. The grade stakes had shifted during a storm. Now I run a quick drone pass after any heavy rain before we pour. Has anyone else had survey markers move like that?

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morganmartinez11d ago

We had a 2.2 acre site in San Antonio do the same thing back in 2021. The rain events were washing out the hub and nail setups on the backside of the lot where we couldn't see them from the road. It took a failed inspection to catch it, not a drone, but the fix was brutal. We ended up locking our grade stakes with concrete and then marking them with high vis paint on the rebar tops. Also, we started checking the GPS base station every morning before we shoot anything, because that thing can drift too after a heavy storm. The drone pass after rain is a smart habit, we do the same thing now and it catches maybe 1 out of 10 issues, but that one is always a money saver. Good on you for figuring it out before the pour.