GRAVITY-FIELD CONVOLUTIONS WITHOUT WINDOWING AND EDGE EFFECTS

A new set of formulas has been developed for the computation of geoid undulations and terrain corrections by FFT when the input gravity anom alies and heights are mean gridded values. The effects of the analytic al and the discrete spectra of kernel functions and that of zero-paddi ng on the computation of geoid undulations and terrain corrections are studied in detail. Numerical examples show that the discrete spectrum is superior to the analytically-defined one. By using the discrete sp ectrum and 100% zero-padding, the RMS differences are 0.000 m for the FFT geoid undulations and 0.200 to 0.000 mGal for the FFT terrain corr ections compared with results obtained by numerical integration.