b.  Concerning a precision radar approach (PAR),  it is the point where the glide path intercepts the  landing surface.  (See ICAO term TOUCHDOWN.)  TOUCHDOWN [ICAO]- The point where the  nominal glide path intercepts the runway.  TOUCHDOWN RVR - (See VISIBILITY.)  Note: Touchdown as defined above is only a datum  and is not necessarily the actual point at which the  aircraft will touch the runway.  TOUCHDOWN ZONE- The first 3,000 feet of the  runway beginning at the threshold. The area is used  for determination of Touchdown Zone Elevation in  the development of straight-in landing minimums for  instrument approaches.  (See ICAO term TOUCHDOWN ZONE.)  TOUCHDOWN ZONE [ICAO]- The portion of a  runway, beyond the threshold, where it is intended  landing aircraft first contact the runway.  TOUCHDOWN ZONE ELEVATION- The highest  elevation in the first 3,000 feet of the landing surface.  TDZE is indicated on the instrument approach  procedure chart when straight-in landing minimums  are authorized.  (See TOUCHDOWN ZONE.)  TOUCHDOWN ZONE LIGHTING - (See AIRPORT LIGHTING.)  TOWER- A terminal facility that uses air/ground  communications, visual signaling, and other devices  to provide ATC services to aircraft operating in the  vicinity of an airport or on the movement area.  Authorizes aircraft to land or takeoff at the airport  controlled by the tower or to transit the Class D  airspace area regardless of flight plan or weather  conditions (IFR or VFR). A tower may also provide  approach control services (radar or nonradar).  (See AIRPORT TRAFFIC CONTROL SERVICE.)  (See APPROACH CONTROL FACILITY.)  (See APPROACH CONTROL SERVICE.)  (See MOVEMENT AREA.)  (See TOWER EN ROUTE CONTROL  SERVICE.)  (See ICAO term AERODROME CONTROL  TOWER.)  (Refer to AIM.)  TRACK OF INTEREST RESOLUTION- A TOI  will normally be considered resolved when: the  aircraft/object is no longer airborne; the aircraft  complies with air traffic control instructions, aviation  regulations, and/or issued flight restrictions/security  procedures; radio contact is re-established and  authorized control of the aircraft is verified; the  aircraft is intercepted and intent is verified to be  TRACK OF INTEREST (TOI)- Displayed data  representing an airborne object that threatens or has  the potential to threaten North America or National  Security. Indicators may include, but are not limited  to: noncompliance with air traffic control instructions  or aviation regulations; extended loss of communica- tions; unusual transmissions or unusual flight  behavior; unauthorized intrusion into controlled  airspace or an ADIZ; noncompliance with issued  flight restrictions/security procedures; or unlawful  interference with airborne flight crews, up to and  including hijack. In certain circumstances, an object  may become a TOI based on specific and credible  intelligence pertaining to that particular aircraft/  object, its passengers, or its cargo.  TRACK [ICAO]- The projection on the earth's  surface of the path of an aircraft, the direction of  which path at any point is usually expressed in  degrees from North (True, Magnetic, or Grid).  TRACK- The actual flight path of an aircraft over the  surface of the earth.  (See COURSE.)  (See FLIGHT PATH.)  (See ROUTE.)  (See ICAO term TRACK.)  TOWER EN ROUTE CONTROL SERVICE- The  control of IFR en route traffic within delegated  airspace between two or more adjacent approach  control facilities. This service is designed to expedite  traffic and reduce control and pilot communication  requirements.  TRACEABLE PRESSURE STANDARD- The  facility station pressure instrument, with certifica- tion/calibration traceable to the National Institute of  Standards and Technology. Traceable pressure  standards may be mercurial barometers, commis- sioned ASOS or dual transducer AWOS, or portable  pressure standards or DASI.  TOWER TO TOWER - (See TOWER EN ROUTE CONTROL  SERVICE.)  Pilot/Controller Glossary Pilot/Controller Glossary  8/15/19 12/31/20  PCG T-5 