Using drones for stockpile measurement

Our aggregates quarry still measures stockpiles with manual surveys once a month, and the figures often differ from sales records. A contractor offered drone surveys that produce volume calculations within a day.

We like the speed and safety benefits, since surveyors no longer need to climb the piles. However, we need to understand accuracy, licensing rules for flying near public roads and whether to buy our own equipment. Has anyone brought drone surveying in-house, and was the learning curve manageable?