High-frequency bistatic scattering on seabed and targets: Comparison of scaled and full-scale experiments with sea trials

Recent uses of bistatic sonars show the advantages of decoupling transmitter and receiver(s) to optimise the information from seabed and target scattering. However, high-frequency scattering needs to be better understood, especially in complex, multiple-target environments (e.g. dumpsites or highly cluttered seabeds). Laboratory experiments are ideal to understand the role of each physical process in the overall scattering, and to optimise data collection strategies depending on the objectives. Experiments can be scaled, using higher frequencies, smaller tanks and smaller targets. But how does it influence bistatic scattering (and its interpretation)? How does the transition to full-scale experiments work out? This is particularly relevant as sea trials are expensive and difficult to conduct. We compare here the results from: (1) scaled experiments of bistatic scattering on bare seabed and targets, performed at Bath; (2) full-scale experiments in the GESMA submarine pens during the EC-SITAR project, with targets in a sand box and (3) sea trials from similar bistatic experiments performed in Elba and Möja Söderfjärd. We conclude by showing the synergy between these three approaches, and the implications of scaled tank experiments for the design of future surveys and instruments, as well as for the analyses of past and future acoustic datasets.