Two-dimensional modelling of synthetic-aperture-radar imaging of ocean waves using the subwindowing technique

Abstract

Abstract The subwindowing method of modelling synthetic-aperture-radar (SAR) imaging of ocean waves is extended to simulate the imaging of two-dimensional wave trains. Simulated images show that the azimuthal smearing induced by random wind waves reduces the image response to swells that are primarily imaged by velocity bunching. The magnitude of this effect is not accurately predicted by degrading the SAR resolution using a scene coherence lime. The smearing does not depend on the wind direction when imaging swell, and does not affect the imaging of range travelling swell. Theoretical analysis shows that adjusting the focus of the SAR processor introduces an offset in the mapping of the surface scatterers that compensates the incoherent azimuthal propagation of the wave being imaged, leading to a higher image contrast. The focus adjustment yielding the maximum contrast is approximately one half the azimuthal phase velocity of the wave when it is propagating within 45° of the SAR flight direction. The dep...