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Sonar Performance Models
Published in Paul C. Etter, Underwater Acoustic Modeling and Simulation, 2017
Cox (1989) noted that the problem of estimating reverberation-limited bistatic sonar performance is more complicated than the monostatic case since it involves summing the contributions of a large number of scatterers ensonified by numerous propagation paths that differ in angle of incidence and position on the beam patterns of the source and receiver. Let R0 represent the reverberation spectral level, then the signal excess can be written to anticipate both noise-limited and reverberation-limited cases as () SE=ESL−TL1−TL2−[(N0+AGN)⊕R0]+TS−Λ−L
A Unified Analysis of Structured Sonar-Terrain Data Using Bayesian Functional Mixed Models
Published in Technometrics, 2018
Hongxiao Zhu, Philip Caspers, Jeffrey S. Morris, Xiaowei Wu, Rolf Müller
In an experiment that studies the echo characteristics of different terrains, a dual frequency bistatic sonar head was used to capture echoes over three different terrain substrates. The sonar head consists of two transducers—a transmitter used to ensonify the environment and a receiver used to receive echoes. The receiver and transmitter were mounted on a portable stand so that the height of the sonar head was approximately 0.5 m above the ground. The sonar head was adjusted to face the terrain substrate with a fixed angle, so that during each measurement, a specific patch (a footprint) of the substrate was ensonified and echoes were collected. Two transmitting/receiving channels were used in the transducers to ensonify the environment and capture the returned echoes, with the fundamental (central) carrier frequencies 25 kHz and 40 kHz, respectively. The dual-channel design brings two potential advantages: (i) it collects data more efficiently—collecting the same amount of data only requires half of the time than a signal-channel sonar; (ii) the two channels allow more diverse sonar responses, leading to potentially more robust target identification performance. More details of the experimental setup are provided in supplementary materials. In this experiment, the height of the sonar head (0.5 m) was set to represent the situation of a small autonomous vehicle, either airborne or terrestrial. For example, such sonar head can be mounted on platforms such as the Pioneer 3-DX ground robot or the DJI S900 hexacopter. Such vehicles are often operated in close proximity to terrain.
Experimental study on hydraulic characteristics of new ecological slope protection structure
Published in Marine Georesources & Geotechnology, 2022
Li Jian, Pingyi Wang, Meili Wang, Linfeng Han
In this experiment, acoustic Doppler velocimetry (Vectrino-II velocimeter) was used for data collection. The Vectrino-II velocimeter is a bistatic sonar, i.e., it uses separate transmit and receive beams. The sonar transmits through a central beam and receives through four beams that are displaced off to the side. The measurement profile is defined by the intersection and by the range gating in time. The transmit transducer sends a short pulse that transits a profiling region of approximately 30–80 mm, and the receivers listen to echoes returned from this pulse gated in time. The Vectrino-II velocimeter uses four receivers, all focused on the same volume, to obtain the three velocity components from that volume.