Height measurement accuracy improvement due to the shape of envelope echo signal

The accuracy of pulsed radar altimeter depends on the shape of average envelope echo signal. Radar cross section of Earth surfaces effects the shape of impulse response. The article describes the method to reduce the effect of the shape of average envelope echo signal using correction factors. The modeling of envelope echo signals was made by using a facet model of plane surfaces for two types of radar cross section. The method of echo signal front slope least squares approximation was used for elevation measurement. Theoretical analysis of elevation measurement distribution show unambiguous dependence between elevation measurement relative error and coefficient of leading edge approximation. Besides, values of elevation measurement relative error form two groups depend on types of radar cross section. Correction factor was calculated by applying exponential function least squares approximation of elevation measurement relative error. Dividing the height measurement by a correction factor results in a decrease in the width of elevation measurement distribution significantly. Thus, proposed method can improve the accuracy of flight altitude measurement. Correction factors can be determined by mathematical modeling on production stage. In addition, presented method requires minimal extra computational cost of multiplying the elevation measurement by coefficient.