Surveying drones can produce high levels of accuracy.

However, not every project requires 1mm precision level, and a range of 15-20mm - achievable with the use of a UAV and ground control - is sufficient.

It does depend on the task at hand.

For some applications, like checking crop growth, or construction progress, high relative accuracy is sufficient.

For other jobs that also require high absolute accuracy, there are drones equipped with Real-Time Kinematic (RTK) and Post-Processed Kinematic (PPK) capabilities. When paired with a few Ground Control Points, survey-level accuracy can be achieved.