Evaluation of side-scan sonar performance for the detection of naval mines

Autonomous Underwater Vehicles (AUVs) equipped with high-resolution side-scan sonars (SSS) are used to carry out preliminary surveys of potentially hazardous areas in order to counter the threat posed by naval mines and reduce risk to personnel. The detection and classification of mine-like objects is conducted offline, after a scan has been completed while the actual identification and neutralization of potential targets is executed in a separate minehunting operation. In this paper the various influences on the imaging sonar system and, moreover, the resulting sonar imagery are assessed with regard to affecting the Probability of Detection and Classification (PDC). Image quality, sharpness and Signal-to-Noise Ratio (SNR) are among the more obvious and straightforwardly quantifiable factors. The complexity of a sonar image, however, can have a significant impact as well. Image lacunarity is used to characterize the seafloor in order to assess the corresponding minehunting difficulty. Additional factors under consideration are the heading angle of the AUV at any given measurement position as well as horizontal spreading and potential overlapping of successive sonic pulses.