Modeling the along-track sidelobe interference artifact in multibeam sonar water-column data

Sidelobe interference artefacts are a common occurrence in multibeam echosounder water-column data. They are very commonly observed in the across-track dimension, where they appear as a semi-circular noise pattern, affecting in particular the data at a range beyond the minimum depth range. However, they also occur in the along-track dimension, where they affect data just above the seafloor near prominent features rising above the seabed. Here, we present a simple model for estimating the probable location of sidelobe interference artefacts in the along-track dimension. We test the accuracy of the model by comparing average energy levels at set distances from the seafloor both within and outside of the modeled location. We discuss how such models have the potential to identify the extent of useable water-column data acquired over complex bathymetry such as rocky reefs, so as to improve analysis of water-column data for the detection of near-benthic features, such as marine vegetation.