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Abstract

A system for flight inspection of radio navigation aids is disclosed in which a interferometric trajectory reconstruction technique (ITR) is employed. The ITR system combines data from a ground-based reference unit at a fixed location with data from a mobile unit on the aircraft. Single-frequency Global Navigation Satellite System (GNSS) receivers in the units provide a sequence of measurement data for each navigation satellite in view. Additional data is collected from the aircraft's radio altimeter when the aircraft passes over the threshold of the runway. The aircraft's trajectory is determined at the end of the time interval under analysis, after all measurements have been received. ITR employs a unique procedure to establish the exact distance from the aircraft to each of several GNSS satellites using both pseudo-range and carrier signal information. The aircraft's position is determined from these distances using a least-squares adjustment procedure. The ITR distance-determination procedure is based on the fact that the aircraft-to-satellite distance is proportional to the total phase of the carrier signal. The total carrier phase consists of an accumulated phase and in initial integer ambiguity. While the accumulated phase is measured directly by the GNSS receiver, the integer ambiguity is resolved by using an iterative search for the correct integer set within a search volume defined by the a-priori uncertainty in aircraft's position. The ITR system uses the aircraft's radio altimeter to constrain the search volume.

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First Claim