OUTER MARKER (OM). An ILS navigation facility in the terminal area navigation system located four to seven miles from the runway edge on the extended centerline indicating to the pilot that he/she is passing over the facility and can begin final approach.
PRECISION APPROACH. A standard instrument approach procedure, which provides runway alignment and glide slope (descent) information. It is categorized as follows:
CATEGORY I. A precision approach which provides for approaches with a decision height of not less than 200 feet and visibility not less than . mile or Runway Visual Range (RVR) 2400 with operative touchdown zone and runway centerline lights.