Quarry client wants monthly volume reports. They've been doing it with GPS surveys and getting results they trust. Now they want to switch to drones for speed.
First comparison: our drone volume was within 2% of their GPS survey on a 50k cubic yard pile. Client says that's not good enough, wants 1% or better.
Is 2% reasonable for photogrammetry volumes? What are you guys seeing in terms of accuracy on stockpile work?
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Sign in2% on a 50k CY pile is actually very good. That's 1000 CY difference which sounds like a lot but consider the inherent error in GPS surveys too - they're not measuring every point on the surface.
To improve: fly lower (150ft), use 80/75 overlap, place GCPs on and around the pile, and define your base plane carefully. The base plane definition is usually where most of the volume error comes from, not the surface.
We regularly hit sub-1% on stockpiles by flying at 120ft AGL and using a consistent base plane methodology. The key is being consistent month over month so relative changes are accurate even if absolute volume has some offset.
Also, compare apples to apples. If they're comparing GPS volumes using a different base plane definition, the numbers will never match.