Abstract: An integrated navigation system is studied in which the accurate height of a helicopter hovering over the sea about l5m is estimated optimally via the Wiener filter.The height measurements are from a strapdown vertical accelerometer and a radio altimeter.The Wiener fil-ter is desigued by means of Bode-Shannon method according to the power spectral densities of random interferenees such as sea waves,radio altimeter noises and accelerometer noises.The in-tegra ted system is simulated under five different cireumstances to test its efrlciency.The results show that the system can attenuate three interferences mentioned above effectively and can track the change of the hovering height quite satisfactorily.

Key words: Wiener filtering, helicopters, hovering, height