The Gibbsboro Joint Surveillance System ARSR-4 radar is used for USAF air defense and Federal Aviation Administration (FAA) air traffic control. The ARSR-4 radar is a three-dimensional system providing azimuth, range and 3-D height. ARSR-4 radar data provided to military end users includes search radar 3D height. Radar data provided to FAA end users is void of search radar 3-D height, but includes weather messages that are not distributed to the military end user.
Also:
http://en.wikipedia.org/wiki/ARSR