A SCHEME for estimating aircraft velocity directly from airborne air-to-ground range measurements is discussed. The idea is based on the premise that the motion of an aircraft can be represented by a polynomial in time, having stationary coefficients over intervals relatively long compared to the measurement sampling interval. The coefficients of the polynomial are estimated by processing range measurements. Radial velocities to two known radio stations at a given location of the aircraft are sufficient to determine aircraft velocity in the plane containing the aircraft and the two radio stations.The results of a study showed that with favorable data rates, a worst case trajectory can be fitted very accurately by a series of connected third order polynomials in time.A proposed two-stage Kalman-Bucy filter implementation for estimating the ground speed vector from aircraft heading information and data from two VOR/DME stations, is described.

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