Noise substraction for improving the localisation of an underwater mobile

An ultra short acoustic base line allows the localisation of an underwater mobile. POSIDONIA is an advanced system that provides the position of a named submersible, towed fish or ROV operating at depths between 50 m and 6000 m. To improve the localization information, an effective and original approach is proposed in this paper. The main problem which appears in this area consists in the fact that the noise characteristics are unknown. Hence, classical methods (for example, spectro-filter) are useless because they provide good performances only in the case where we know a noise reference. In this work, we use shift-invariant wavelet packets decomposition (SIWPD) and entropy criteria for noise rejection; we compare the results obtained with those obtained using SUREThresholding (WPD) denoising method