The NAV Marker Transmitter is a small tracking device of the United Nations Space Command. They are small devices, relatively the size of a tick, and can be discreetly attached to an object and will Broadcast the location of that object to a nearby UNSC Heads-up display calibrated to their frequency. NAV Marker Transmitters have been used by SPARTAN-II's during operations, such as the raid on United Rebel Front Jefferson Station.