Propeller Aero

It depends on the project pace. Large earthwork is often flown weekly or biweekly; for monthly billing, at least once a month aligned with the pricing cycle so the numbers mean something.

A traditional total station has higher single-point precision but can only measure the points it surveys. Aerial survey has full coverage with slightly worse single-point precision, but computing overall volume is actually more reliable. It depends on whether you're measuring points or volume.