Setting Ground Control
More in depth information on ground control can be found here.
GCPs should be shot and marked with high precision and accuracy
The visual representation of the GCP should be completely unambiguous and easily identifiable from the drone pictures
If using a tile or something movable as a GCP, be sure it is anchored to the ground so it cannot easily be moved.
Be sure you set your ground control only in areas you plan on flying directly over.
Try to put GCPs on low and high elevation points in the project if possible
Set a minimum of 5 GCPs per flight battery used (Non RTK drones only)