Modelisation of the spatial autocorrelation function of the heights of the sea

The spatial autocorrelation function of the heights of sea is pertinent information necessary to determine the electromagnetic scattering from a sea surface (Kirchhoff´s model and shadowing function). In the literature the autocorrelation function is classically set anisotropic gaussian or anisotropic exponential. In this paper, the authors present the modelisation of the autocorrelation function, calculated for two bidimensional spectral configurations of the sea. The Apel spectrum is based on recent works. The Pierson spectrum added to its angular function, was developed in the 70s, and is still the most widely used the most at this moment. The determination of the autocorrelation function requires two integrations. The first angular integration is analytical, whereas the second over the wave number is numerical. In this lies calculating the originality of the authors´ method. Calculating the analytical integration (instead of using a FFT inverse) allows the authors to find directly the behaviour of the autocorrelation function according to the viewing direction