Knowledge of surface sediment distribution in Galveston Bay is important because it allows us to better understand how the bay works and how human activities impact the bay and its ecosystems. In this project, six areas of bay bottom were surveyed using acoustic techniques to make maps of bay bottom types and to investigate the types and extent of anthropogenic impacts. A total of 31 km2 was surveyed in six areas, one in Bolivar Roads (6.1 km2), one near Redfish Bar (3.1 km2), two in East Bay (12 km2), one southeast of the Clear Lake entrance (5.3 km2), and one in Trinity Bay (4.3 km2). Sidescan sonars (100 kHz and 600 kHz) were used to image the bay bottom, and a chirp sonar (2-12 kHz) was used to image subsurface sediment layers and bottom topography. In the side-scan records, objects as small as a few meters in extent were visible, whereas the chirp sonar records show a vertical resolution of a few tens of centimeters. The sidescan images display strong backscatter in some areas due to coarse sediments in addition to weak backscatter in areas of fine sediment. The bay bottom was classified using three levels of sonar backscatter ranging from high to low. Areas of differing sonar backscatter intensity were sampled with cores and grab-samples. High backscatter corresponded to coarse shell debris and oyster reefs, medium backscatter corresponded to a sand-silt-shell mixture, and low backscatter corresponded to silty loam. Chirp sonar records were classified as one of nine different bottom reflection types based on changes in amplitude and stratigraphy. Parallel, layered sediments are seen filling the bay valley and resting atop a sharp contact at which the acoustic signal fades out. Along the flanks of the valley fill the acoustic response revealed an absent or weakly laminated stratigraphy, whereas areas of high oyster productivity produced mounds, strong surface returns, and strong, shallow subsurface reflectors surrounding current oyster reefs. Anthropogenic features imaged with the sonar included sediment disruptions, such as the ship channels, dredge holes, gouges, and trawl marks, as well as debris, such as submerged boats, pipes, and unidentified objects.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

This work investigates the ideal distribution of sensors in networked arrays. MATLAB models these arrays and simulates the results these networks obtain using active and passive sonar. These results determine the ideal sensor placement for optimal parameter detection and estimation of targets. This work's first part focuses on active sonar networks with a fixed number of sensors in a differing number of arrays. MATLAB simulates the data of these sensors taking into account the geometries and velocities of the arrays and targets, then estimates the parameters of the targets using an elliptical filter, a conventional beamformer, a matched filter and one of three fusion methods. This work compares the performance of each network and fusion method. This work shows that the adding more arrays, regardless of size, enhances the overall performance of the network. It also shows the larger arrays obtain more robust parameter estimation. The second part of this work investigates the effects of uncertainty of the array position and orientation using passive sonar. Two networks, one with 2 32-channel arrays and one with 8 2-channel arrays, estimate a sound source's location using a conventional beamformer. MATLAB simulates the data taking into account the geometries of the arrays and the sound source. The results of these simulations show that when uncertainty of position and orientation increases, the better the smaller arrays estimate the location of the sound source compared to the larger arrays. / Master of Science

No description available.

No description available.

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 2009

Denna rapport presenterar en metod som möjliggör bestämning av bredbandiga signalers infallsvinklar. Studien är gjord i Matlab där infallande signaler samplades med ett antal sensorer utplacerade ekvidistant på en rätlinje. Den samplade informationen viktades sedan med konstanter framtagna med en konvex optimeringsrutin för att bilda en vinkelberoende utsignal. Rutinerna testades för insignaler med ett få antal frekvenser och gav för alla testade insgnaler en mycket bra bestämmning av infallsvinklen. Studien visar även att det är möjligt att göra systemet mer robust mot störningar i sensorernas positioner genom att ställa kriterier på den konvexa optimerings rutinen.

About the investigation method of the present situation of coral reef at present, the main choice is scuba diving investigation no matter domestic and foreign countries. Take the coral reef of physical examination in Taiwan as example, divers use transects as basic methods to calculate the coverage rate of coral reef and characteristic of the seabed environment and to survey specific fish and quantity of the invertebrate in order to judge the influence that the human activity causes to the coral reef. In above-mentioned methods can really make full and accurate investigation to the coral reef of monitor area, so the method has already been adopted and walked for many years by the domestic and international relevant organization. But its shortcomings are slower investigating speed and lack accurate fixed position methods, and the divers also have hiding danger. However, some characteristics of side-scan sonar system just can mend the weak points of them. For the speed of investigating, our side-scan sonar's survey range can reach the belt area of hundred meters wide in both route sides, so it can substantially improve the speed of investigating. For the accuracy of fixed position, the side-scan sonar system match to GPS can obtain certain longitude and latitude of targets¡]the precision about 10 m¡^. So, this research is using side-scan sonar system to survey the seabed around LIU-CHIEU YU¡]the survey area about 2.6 km2¡^, the steps contain: mapping the distribute condition¡]sand, mud and rock¡^of seabed bottom, then identifying growing coral reef of rocky area, final assessing its feasibility by the process and result of survey. The ultimate purpose is an attempt to provide a new method for coral reef survey. The result of study shows: the seabed bottom around LIU-CHIEU YÜ can be divided into several parts by the difference of acoustics reflectivity. Among them, coral reef covers maximum area, and the area can reach to 1,133,670m2¡]46.4% of effective survey area¡^. In the part of identifying growing coral reef in the acoustics image, this study compares with optics images of TOV and acoustics images of side-scan sonar to establish the characteristics of growing coral reef in the acoustics image. Among them, the tree-like corals have some characteristics about high backscatter, individual risings, tree-like figures and acoustics shadows, unregulated reflection surfaces and complicated color tones in the reflection surface, but the cover-form reefs do not have tree-like figures and acoustics shadows. Then, using the above-mentioned characteristics to identify survey area seabed shows¡GThe cover area of growing coral reef is 547,438 m2¡]22.4% of effective survey area¡^, and the growing coral reef distributes in the southwest, southern and eastern sea area of LIU-CHIEU YÜ. And the optics images of the TOV shows the growth state of growing coral reef in the southeast sea area is superior to the southwest sea area, Finally, assessed by the process and result of this research, basically it is feasible to map the distribute condition of growing coral reef by side-scan sonar system.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 59-63).

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Steven R. Baker, Thomas G. Muir. Includes bibliographical references (p. 57-58). Also available online.