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Navigation
Published in R. Glenn Wright, Unmanned and Autonomous Ships, 2020
Security Sonar – The detection, tracking and classification of divers as well as underwater vehicles that may pose threats may be accomplished using security Sonar. Such systems are available from a variety of manufacturers and their ranges vary from a few hundred to a thousand or so meters to create a secure perimeter through 360 degrees around a vessel. Weaknesses may exist in their ability to detect divers using closed-circuit systems such as rebreathers, and to distinguish between divers or underwater vehicles and larger marine mammals, fish and schools of fish. Enhancements to existing algorithms using artificial intelligence and other methods to better distinguish between different targets based upon their unique signatures expressed in Sonar signals have often proved successful in enhancing the performance of these Sonar systems.
Introduction
Published in Paul C. Etter, Underwater Acoustic Modeling and Simulation, 2017
Naval operations in littoral regions often rely on multistatic acoustic sensors, thus increasing the technical challenges associated with the field-intensive experiments necessary to test multistatic geometries. Acoustical oceanographers have conducted supporting research using traditional direct-sensing methods in addition to more sophisticated inverse-sensing techniques such as acoustic tomography, full-field processing, and ambient-noise imaging (see Section 1.6). Due to an increased awareness of the potential technological impacts on marine life, naval commanders and acoustical oceanographers must now comply with new environmental regulations governing the acoustic emissions of their sonar systems.
Acoustic Signal Processing
Published in Richard C. Dorf, Circuits, Signals, and Speech and Image Processing, 2018
Juergen Schroeter, Gary W. Elko, M. Mohan Sondhi, Vyacheslav Tuzlukov, Won-Sik Yoon, Yong Deak Kim
The use of acoustical signals that have propagated through water to detect, classify, and localize underwater objects is referred to as underwater acoustical signal processing or sonar. Sonar stands for “Sound Navigation Ranging” and is a method or device for detecting and locating objects, especially underwater, by means of sound waves transmitted or reflected by an object. Specific sonar application problems are submarine detection, mine hunting, torpedo homing, and bathymetric sounding. There are active and passive sonars. Active sonars transmit acoustic energy and detect targets by echolocation. Passive sonars operate by listening for acoustic emissions and can function in a covert manner.
Exploration of Beamforming Approach to Enhance the Detection Rate of Underwater Targets in Distributed Multiple Sensor Systems
Published in Smart Science, 2020
Submarine detection and localization is one major application of sonar systems. The objective is to infer if a target is absent or present, given a number of sensor distributed in the underwater network. The target emits a sound signal, and based on sound measurements a decision has to be made on absence or presence of the target. Measurements are perturbed by random background noise which makes the detection of the target signal nontrivial. Detecting a signal in noise is essentially a statistical hypothesis testing problem [1]. Absence or presence of the target corresponds to null hypothesis (H0) and alternative hypothesis (H1), respectively. This is a binary hypothesis testing problem since there are only two different hypotheses. We consider a distributed fusion system with N sensors and a fusion center. We limit to the binary hypothesis case with the unknown parameters present only under the alternate hypothesis. Suppose we have an observation vector X, the measurement equations under different hypothesis is given by,
All at Sea with User Interfaces: From Evolutionary to Ecological Design for Submarine Combat Systems
Published in Theoretical Issues in Ergonomics Science, 2019
Daniel Fay, Neville A. Stanton, Aaron P. J. Roberts
Sonar is a system for the location and ranging of objects using sound propagation and listening. Its four main functions are Detection, Classification, Localisation and Tracking (DCLT: (Hughes et al. 2010)). To detect a vessel an operator will either hear discreet noise against the oceans background noise and/or see a concentration of sound on their waterfall forming a line, at a specific Direction of Arrival (DOA), using broadband Sonar, see Figure 2a. Because of advances in modern boats (such as quieter engines, more efficient anechoic tiles, and advanced hull designs), it is possible for some signals from them will be quiet and intermittent, which could result in them not being detected. This is because they may not be readily discernible as clear traces (Matthews et al. 2006). The system does not currently highlight such traces to an operator, which may affect submarine safety if they fail to detect them.
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
Sonar (Sound Navigation and Ranging) is a technique that uses sound propagation to detect, localize, and identify objects for purposes such as navigation. An active sonar system transmits acoustic waves with a known time waveform and receives the echoes reflected by obstacles. During propagation and reflection, the transmitted waves will be transformed due to physical effects such as propagation delays, frequency-dependent attenuation, frequency-shifts, and the addition of noise. These modifications are captured in the received echoes and can be used to infer the characteristics of the targets (Le Chevalier 2002) and the propagation channel. In complex, natural environments, an echo signal often consists of reflected waveforms from numerous scatterers that are distributed in space (e.g., tree leaves, rocks), thus can be nonstationary, non-Gaussian, and highly stochastic (Müller and Kuc 2000; Yovel et al. 2008). This makes identification and navigation with over-simplified physical models unrealistic. Statistical approaches are therefore highly desirable to study sonar responses to targets, and extract useful information about the environment (Robertson 1996; Vicente Martinez Diaz 1999).