Abstract: Apparatus, and a corresponding method, for generating navigational data to aid a pilot in landing or taxiing an aircraft in poor visibility conditions. Radio-frequency (rf) beacons at predetermined locations around an airport runway or taxiway are separately modulated to render them uniquely identifiable from the aircraft. A fixed array of receiving antennas on the aircraft has multiple, angularly spaced antenna beams that substantially overlap each other in coverage, such that a signal received from one of the beacons will in most cases be received in more than one adjacent receive beam. Signals received in each beam are processed by a fast Fourier transform module to separate signal components from the various beacons; then an interpolation process determines the arrival angles of the signals by comparing the amplitudes received in adjacent receive beams.