Synthetic aperture sonar imaging of buried spheres and cylinders

Abstract

During SAX04, synthetic aperture sonar (SAS) was used to detect buried spheres where the nominal grazing angle of incidence from the SAS to the point above a sphere was well below the sediment’s critical grazing angle. SAS images from other measurements below the critical angle on buried spheres and finite cylinders in the NSWC-PC test pond facility have also produced target detections. Numerical simulations will be discussed that accurately predict the observed signal to noise (SNR). Simulations include estimates of reverberation from the rough seafloor, and the subcritical penetration through the seafloor, scattering from a target, and propagation back to the SAS. Required material parameters were obtained from environmental measurements including profiles of the small-scale surface roughness and the superimposed ripple structure. These simulations, the sonar equation results, and the model/measurement comparisons over the frequency range of 10–50 kHz further support sediment ripple structure as the dominant mechanism for subcritical penetration in this range. [Work supported by ONR.]