Using acoustic diffraction to determine the seabed slope

In this paper, we present a new seabed detection method based on the use of a single beam electro-acoustic transducer (echo sounder). This method uses both acoustic diffraction and bottom backscattering properties to determine the 2D or 3D equation for seabed slopes. It can thus be used for bottom tracking (e.g. for autonomous underwater vehicles). In comparison to existing sonar-based processes, our method offers the advantages of mono-beam transducers : low computational cost, lower power consumption and higher sampling rate.En tenant compte du profil de rétrodiffusion acoustique du fond marin, nous montrons que, sous certaines conditions d'inclinaison d'un transducteur monofaisceau, il est possible d'exploiter le ou les lobes secondaires du faisceau acoustique diffracté afin de déterminer non seulement la distance du fond marin par rapport au capteur mais aussi son inclinaison relative (dans l'espace à 2 ou 3 dimensions). Cette propriété peut être exploitée à bord des petits véhicules autonomes sous-marins pour accomplir du suivi de fond

Using Sound Diffraction to Determine the Seabed Slope

International audienceNavigation of autonomous underwater vehicles (A.U.V.) in very shallow waters implies acoustic detection. In single beam sonar systems, sound emitted by ultrasonic transducers is diffracted and secondary lobes appear. Considering the sea bottom's backscattering properties, secondary lobes can be used to enhance knowledge of seabed features such as slope, and marked variations. In this paper, we firstly consider characteristics of electro-acoustic transducers and study the resulting acoustic diffraction. Then, we introduce a new method aiming to extract seabed features from the received acoustic echo. Thus single beam sonar systems can be used for bottom tracking purposes. We present the results of our simulations and experimental validation