Papers by Fannie Shabangu
Echo integration in bad weather conditions is problematic due to vessel-and wind-induced air bubb... more Echo integration in bad weather conditions is problematic due to vessel-and wind-induced air bubble layer that is formed below the hull of a vessel, where acoustic transducers are mounted. The bubbles below the hull attenuate both the transmitted and received acoustic waves and may lead to an underestimation of the real fish abundance or density. A detailed understanding of the acoustic energy attenuation by the air bubble layer is crucial for establishing a correction factor for the recorded echo integrator measurements. The acoustic attenuation by the air bubble layer under different weather conditions were estimated by observing the ratio of the nautical area backscattering strength of the sea bed between two inter-calibrated Simrad EK60 38 kHz hull-and keel-mounted transducers. By integrating the sea bed as a reference target over distance in various weather conditions, the amount of acoustic signal attenuated by the air bubbles was estimated. A correction factor for the hull mounted system was further established from the data.
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Papers by Fannie Shabangu