Surface-induced errors in target strength and position estimates during horizontal acoustic surveys

0479371 - BC 2018 RIV NL eng J - Článek v odborném periodiku
Balk, Helge - Sovegjarto, B.S. - Tušer, Michal - Frouzová, Jaroslava - Muška, Milan - Draštík, Vladislav - Baran, Roman - Kubečka, Jan
Surface-induced errors in target strength and position estimates during horizontal acoustic surveys.
Fisheries Research. Roč. 188, APR (2017), s. 149-156. ISSN 0165-7836. E-ISSN 1872-6763
Grant CEP: GA MŠMT(CZ) EE2.3.20.0204; GA ČR GAP504/12/1186
Institucionální podpora: RVO:60077344
Klíčová slova: hydroacoustics * surface boundary * shallow water * horizontal beaming * simulations
Obor OECD: Fishery
Impakt faktor: 1.874, rok: 2017

Horizontally-aligned, fixed and mobile, transducers are routinely deployed at depths of 0.5-0.75 m to survey the surface layer of waterbodies for fish. However, simulations and measurements demonstrate that a smooth surface can cause serious errors in the target strength (TS) and split-beam angular position estimates. Errors in TS up to 10 dB and depth position up to 0.5 m were observed. Simulations suggested that multi-path signal propagation interfered with the direct path of that signal. Furthermore, when a standard target (calibration copper sphere) was moved away from the transducer at fixed depths, the estimated TS and depth of the target started to oscillate as a function of range. The amplitude increased with increasing range. The frequency decreased from the oscillation start until a certain range where the oscillation stopped. The region of oscillation depended on both the transducer and target depth. Horizontal observations of known fish echoes behaved similarly. Experiments in a lake showed that the influence from the surface disappeared when the surface became rippled due to wind.
Trvalý link: http://hdl.handle.net/11104/0275349