This means that no part of the vehicle can be more than four miles away from where you are standing when operating it.
If you have an unmanned aircraft system (UAS), you must keep it within your line of sight. Keep Your Drone Within Your Line Of Sight
This distance requirement does not apply to law enforcement officials operating an unmanned aircraft for official business purposes in cases where: You also can’t fly over any persons who are not involved in your operation of the drone. You must stay at least 400 feet from any structure, vehicle, or person not associated with the operation of the aircraft.
