초록 ▼

The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are us

The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are used with the smoothed baro-inertial output from an inertial reference system to provide 3 dimensional constant rate of descent approach procedures to replace non-precision approach procedures based on constant barometric altitude step approaches. The horizontal positions used as reference for the stored terrain altitude profiles are obtained from a prior art navigation apparatus. The integrity of all measurements is assured by using long term averages of the Kalman filter residuals to detect failures. In addition, the estimated baro offset at the runway is compared for consistency with the baro offset obtained by the pilot from the airport by radio.

대표청구항 ▼

[ What is claimed is:] [1.] A method for determining a vehicle's altitude above a predetermined reference level utilizing values of navigation quantities from one or more external sources, an altitude being referenced to the predetermined reference level unless otherwise noted, the method comprising

[ What is claimed is:] [1.] A method for determining a vehicle's altitude above a predetermined reference level utilizing values of navigation quantities from one or more external sources, an altitude being referenced to the predetermined reference level unless otherwise noted, the method comprising the steps:(a) obtaining values of a plurality of external-source navigation quantities at periodic input intervals, the external-source navigation quantities including a first external-source vehicle altitude;(b) obtaining observations at periodic observation intervals of one or more observation quantities, at least one of the observation quantities being a function of a second external-source vehicle altitude, an observation interval containing one or more of the periodic input intervals;(c) deriving correction data at the periodic input intervals from the observations of step (b);(d) obtaining values of one or more corrected or computed navigation quantities at the periodic input intervals using the correction data of step (c), the one or more corrected or computed navigation quantities including a corrected first external-source vehicle attitude.