Imagine that you are flying a model helicopter or a drone. You are there with the auto controls. You switch them on. The rotors start to turn, gradually increasing their spin. You watch, then push the control for lift. Your helicopter rises, hovers, then at the next command moves forward. Oops, it didn't go high enough. You quickly move the joystick and the drone rises to fly above the obstruction. Finally it's in the air, moving at speed above sand dunes, hills and valleys—sending back pictures as the landscape unfolds.