Investigating element-level signal coherence in multibeam echosounder data

Theoretical models have indicated that spatial coherence of seafloor scattering can be sensitive to environmental properties such as roughness and slopes in bathymetric data. As observing spatial coherence requires a sonar array with many receivers, raw, uncalibrated element-level data from a Kongsberg EM 2040 multibeam echosounder is used to investigate how the coherence between elements' signals changes as a function of their separation distance. While previous models and measurements have investigated this phenomenon, this study investigates whether a multibeam echosounder is a suitable sensor for observing spatial coherence at higher frequencies than have previously been analyzed. This talk will present the relationship found between element separation and spatial coherence at these frequencies, as well as the extent to which pre-existing theoretical models were found to describe the data. Additionally, the pattern in spatial coherence is investigated for acoustic pulses scattered at an oblique angle. Applications of this work could lead to real-time performance estimation of multibeam sonar systems and could improve the accuracy of in situ calibration.