Elevation interpolator for simulated radar display system

Abstract

A signal processing mechanism for interpolating elevation data values between successive data points of a terrain map from which a simulated radar return image may be produced employs a signal processing operator in accordance with which input data signals representative of the elevations at successive data points on the terrain map are processed, to derive a continuous interpolated (terrain map) functional characteristic. Interpolated elevation data values at one or more points between successive ones of the original data points are calculated by employing elevation values for successive data points adjacent to those data points between which the one or more additional points of interest are located. The elevations of these additional `intermediate` data points are derived using a polynomial the coefficients of which are determined in accordance with the harmonic mean, such that the magnitude of each of the elevations of the original terrain map is preserved, the slope of the interpolated terrain map characteristic at the original data points is continuous, and such that the sign of the slope of the interpolated terrain map characteristic between original data points does not change. Signal processing circuitry for executing the signal processing operator includes a coefficient calculation unit, a polynomial calculation unit and an elevation value buffer unit, the operation of each of which is processor-controlled.