Method and system for predicting ship motion or the like to assist in helicopter landing

摘要

A method for a short-term prediction of future ship motion in open water to furnish visual cueing information that can be remotely presented to a pilot during an aircraft landing is described. Two sets of samples of the sea surface geometry along a radial azimuth line from a ship as a function of elevation of a sensor are first acquired. These are compensated to remove the components due to the ship's motion. Two wave traces are then separately derived in Cartesian format from the two sets of acquired samples. These wave traces are subjected to a Fast Fourier Transform to detect the amplitudes and phases of the individual wavelength components. The direction of the wavelength components is determined using a measure of their phase change in the scan direction during the time interval between the two scans together with their measured wavelength. The amplitude, direction and phase of each component is utilized together with the known motion characteristics of the moving ship in order to derive a short-term prediction of future ship motion in the time domain. A quiescent period of the ship motion is located by comparing the short-term prediction with the pre-defined operating limit criteria. Finally, a message signal is transmitted to the pilot of the aircraft indicating Time-to-Land and the duration of the quiescent period.