Data analysis for the long-range sidescan sonar data /
The [TAMU]2 system is a long-range, high-resolution,
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965641&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The [TAMU]2 system is a long-range, high-resolution, sidescan-sonarimaging and bathymetric, swath, seafloor- mapping system designed for scientific, commercial, and military seafloor mapping applications. There are some inherent problems, noise, artifacts, and bathymetric and geometric distortions contained in the collected sidescan sonar data no matter how well designed a sidescan sonar system is. Previously published methods have solved certain sidescan sonar problems, but several problems remain unresolved or poorly resolved, and a number of improvements in processing methods can be made. Speckle noise, multiples, false bottom returns, striping noise, gray-level difference, and image contrast are the six different types of noise and artifacts encountered in the [TAMU]2 data. New or modified methods are proposed and reconsidered in this study to remove these artifacts and noise. A modified version of the Powell method is suggested for speckle noise removal. The processed result of the modified Powell method not only removes speckle noise but also preserves the edges contained in the original images. Three major procedures are used to remove primary multiples: calculating the residuals, calculating the interpolated values by the minimum curvature method, and then adding the residuals. Methods that detect false bottom edges, resample pixels, and interpolate empty pixels are applied to remove false bottom returns. The Search-and- Replace method is introduced to remove striping noise. Two procedures are applied to the gray-level difference problem: identify locations of pixels having gray-level differences with edge detection, and fix one side by adding or subtracting the mean difference from the other side. Two general methods, Haralick et al. [1 973] and Chavez [1 9861, have been used to enhance image contrast and improve visual quality. Corrections in bathymetry and data-positioning are made on the [TAMU]2 data to produce a meaningful geometrically correct image. The goals of bathymetry correction are to correct the ray-bending problem and reduce errors in estimating each pixel's depth and across-track position. The purpose of data-positioning correction is to assign each pixel to its appropriate geographic location. When the images are corrected, mosaicked, and assembled as a map projection, it is more convenient to compare them with other map-based data such as NGDC and SeaBeam. 2-D mosaicked images and 3-D real-time displays are also generated to aid in understanding of the tectonic processes of the surveyed area and to make appropriate geological interpretations. |
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| Item Description: | Vita. "Major Subject: Geophysics". |
| Physical Description: | xv, 194 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |