The multiple-aspect scattering (MAS) dataset collected at the field test site in Moja Soderfjard concentrated on the half-buried box in a known location, as described in Section 11.3. As reported there, due to equipment malfunction, the data have been gathered using the spare vertical array in a configuration different from the one originally planned (fewer receivers, different spacing and elevation above the sub- bottom). From the point of view of 3D acoustical imaging, this had a negative effect: the scatterers identified from the object in this configuration were not dense enough, and had too much uncertainty, to produce a volumetric 3D acoustic image to be used for extraction of object information through decision support system processing. On the other hand, the identified scatterers were sufficient to produce a 2D image in which the object itself and its position could be determined with remarkable accuracy. Moreover, the raw acoustic data were used, in conjunction with the acoustic scattering models described in Chapter 4, to perform a model-based inversion for determination of the scatterer geometrical parameters. The success of this latter approach demonstrates that, even in sub-optimal configurations, the MAS technique does provide sufficient information for the acoustical inspection of buried and proud objects.
In the following we concentrate briefly on 3D acoustical image processing and then, in more detail, on estimation of object parameters.