Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 283 for “"Sonar"”.
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Dynamic sonar perception
Reliable sonar perception is a prerequisite of marine robot feature-based navigation. The robot must be able to track, model, map, and recognize aspects of the underwater landscape without a priori knowledge. This thesis explores the tracking and mapping problems from the standpoint of …
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High Resolution Continuous Active Sonar
… signal processing methods for continuous active sonar (CAS). The work presented focuses on methods for achieving high range, Doppler, and angular resolution, while maintaining a high signal-to-interference plus noise ratio (SINR).</p><p>CAS systems transmit at or near 100\% duty cycle for …
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A bathymetric sidescan sonar system
… and construction of a bathymetric sidescan sonar system capable of operation over a 39 degree vertical sector is described. Field tests conducted at a dam site indicate that the completed system does not function as required. This is due to errors in the sonar depth measurement which are …
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Techniques for tailoring sonar transducer responses
This work is concerned with the design of sonar transducers operating in the frequency range 100 kHz to 1 MHz. The transducer frequency responses are predicted using a one-dimensional transmission line analysis. Differences between predicted and measured results are shown to be caused by intermodal …
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Super-resolution phased array sonar imaging
… reconstruction for a multibeam phased array sonar. A generic data model for phased array sonars is first developed and is used to derive conventional signal processing concepts for image reconstruction which are necessary for the implementation of the super-resolution algorithms. The most …
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Human factors engineering in sonar visual displays
… data from a wide variety of sensors including sonar (sound navigation and ranging), cameras, and lasers. Effective collection, computation, and presentation of this data to the pilot in a single display presents hardware, software and human factors problems. This thesis focuses on human factors …
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Dense, sonar-based reconstruction of underwater scenes
… the pose of a mapping sensor such as a multibeam sonar. For underwater platforms, the rapid attenuation of electromagnetic signals in water precludes the use of GNSS receivers at any meaningful depth. Acoustic positioning systems, the underwater analogues to GNSS, are limited to small survey areas …
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Modeling a 300 kHz bathymetric sonar system
… family of calibrated high frequency bathymetric sonar systems for underwater survey. It is useful to have a detailed mathematical description of these systems to assist in data processing. A model of a generalized sonar system is developed first. This model then is made specific to the DSL …
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Target detection in clutter for sonar imagery
… is concerned with the analysis of side-looking sonar images, and specif- ically with the identification of the types of seabed that are present in such images, and with the detection of man-made objects in such images. Side-looking sonar images are, broadly speaking, the result of the physical …
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Synthetic aperture sonar for sub bottom imaging
… with implementing synthetic apertures in sonar may be overcome by applying the technique to sub-bottom imaging. The use of a low frequency aids both penetration of the sediment and the attainment of long coherent apertures. The implementation of synthetic apertures realises a narrow fan …
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Sonar beamforming based upon monaural localisation techniques
Sonar beamforming is usually accomplished using a multi-element transducer array. To obtain high resolution, such a system is costly and complex. In contrast, many mammals are capable of good angular resolution using only a single active element surrounded by an irregular reflector – the ear. A …
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A direct-coupled multiplier for acoustic sonar
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering, 1960.
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Dense, sonar-based reconstruction of underwater scenes
… the pose of a mapping sensor such as a multibeam sonar.
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Sonar systems performance in the Mediterranean Sea
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997.
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A code-division, multiple beam sonar imaging system
In this thesis, a new active sonar imaging concept is explored using the principle of code-division and the simultaneous transmission of multiple coded signals. The signals are sixteen symbol, four-bit, non-linear, block Frequency-Shift Keyed (FSK) codes, each of which is projected into a different …
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Registration and variability of side scan sonar imagery
… of several experiments performed on side scan sonar equipment and imagery with the aim of characterizing the acoustic variability of side scan sonar imagery and applying this information to image rectification and registration. A static test tank experiment is presented which analyzes the …
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Sonar Jamming in the Bat-Moth Arms Race
… 2) startle bats, or 3) interfere with or jam bat sonar. Evidence is strong for the warning and startle hypotheses, although the startle effect is ephemeral. The jamming hypothesis has not been confirmed to occur in nature.
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Side scan sonar image formation, restoration and modelling.
… the development of processing algorithms for sonar image enhancement. The thesis is divided into two principal parts. In the first part the statistical properties of side scan sonar images are analysed. Then, based on this analysis, a Maximum A Posteriori (MAP) formulation of the sonar image …
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