SkyTracker employs radio frequency sensors at strategic locations around an airport and determines the location of both the UAS and the operator.  http://www.uasvision.com/2016/02/22/anti-drone-system-for-airports-passes-tests/?utm_source=Newsletter&utm_campaign=02145de55d-RSS_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_799756aeb7-02145de55d-297556397