ABSTRACT
The command and control functionality of unmanned aircraft systems allows operators to know what is happening on board the aircraft while flying. Focus will be given to radio frequency (RF) data links, because they are the most common form of communication for unmanned systems. Other mediums such as tethered cables and beams of light are sometimes used for information transfer. Regardless of the underlying navigation technology used for controlling the unmanned aircraft, the primary method for an operator to create navigation commands for the aircraft is to use a graphical map with waypoints to mark the course of the aircraft. Virtually all civil unmanned aircraft use line of sight (LOS) RF communications for their command and control data link. LOS in the context of RF signals simply refers to a direct path between one antenna and one or more others.
