An algorithm for the extraction of ocean wave information from bistatic HF groundwave radar data: a simulation

Zhang, Jianjun, 1967 July 31- (2003) An algorithm for the extraction of ocean wave information from bistatic HF groundwave radar data: a simulation. Masters thesis, Memorial University of Newfoundland.

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Abstract

In this thesis an algorithm is developed for the inverse problem of bistatic scattering from the ocean surface. Narrow beam bistatic high frequency (HF) radar data from the ocean surface are simulated and the non-directional ocean wave spectrum is recovered. The water depth is set to be arbitrary. Zero-mean Gaussian noise from external sources is taken into account. -- The bistatic HF radar cross sections are applied to the general-depth water case. The second-order cross section of patch scattering is a two-dimensional Fredholm-type integral equation of first kind. It contains a non-linear product of ocean wave directional spectrum factors in its integrand. The energy inside the first-order cross section is derived to normalize this integrand. The unknown ocean wave spectrum is represented by truncated Fourier series. The integral equation is then converted to a matrix equation and a singular value decomposition (SVD) method is invoked to pseudo-invert the kernel matrix. The non-directional ocean wave spectrum is obtained from the Fourier coefficient α₀. -- The zero-mean Gaussian noise from external sources is added to simulate pulsed HF radar clutter from the ocean surface. The power spectral densities of the clutter and noise are obtained by means of a periodogram. The combination of power spectral densities of clutter and noise makes the simulated bistatic radar data correspond more closely with actual observations. The inverse algorithm is carried out with respect to radar data for varying water depths, wind velocities, and radar operating frequencies. The results are compared with the original ocean wave spectrum.

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