81 research outputs found
Mapping submarine glacial landforms using acoustic methods
The mapping of submarine glacial landforms is largely dependent on marine geophysical survey methods capable of imaging the seafloor and sub-bottom through the water column. Full global coverage of seafloor mapping, equivalent to that which exists for the Earth's land surface, has, to date, only been achieved by deriving bathymetry from radar altimeters on satellites such as GeoSat and ERS-1 (Smith & Sandwell 1997). The horizontal resolution is limited by the footprint of the satellite sensors and the need to average out local wave and wind effects, resulting in a cell size of about 15 km (Sandwell et al. 2001). A further problem in high latitudes is that the altimeter data are extensively contaminated by the presence of sea ice, which degrades the derived bathymetry (McAdoo & Laxon 1997). Consequently, the satellite altimeter method alone is not suitable for mapping submarine glacial landforms, given that their morphological characterization usually requires a much finer level of detail. Acoustic mapping methods based on marine echo-sounding principles are currently the most widely used techniques for mapping submarine glacial landforms because they are capable of mapping at a much higher resolution
Acoustic calibration and bathymetric processing with a Klein 5410 sidescan sonar
In 2001, NOAA acquired an L-3 Communications Klein 5410 bathymetric sidescan sonar system that simultaneously provided high resolution multibeam acoustic imagery and wide swath bathymetry. The sonar\u27s inability to produce matching bathymetry in overlapping swaths motivated the detailed acoustic and signal processing analyses described in this thesis.
Results of this research include specific corrections for phase distortions introduced by the sonar\u27s transmit pulses, receiver electronics, and transducer elements, which are implemented in a newly-developed full vector bathymetric processing algorithm to estimate accurate acoustic arrival angles for each sample of the seafloor echo acquired by the Klein 5410 sonar. Performance of this algorithm was verified during a survey conducted in New York Harbor during October of 2006. The resulting bathymetry matches bathymetry obtained independently over the same survey area with a Reson SeaBat 8125 focused multibeam echo-sounder operating at the same acoustic frequency
Advances in Sonar Technology
The demand to explore the largest and also one of the richest parts of our planet, the advances in signal processing promoted by an exponential growth in computation power and a thorough study of sound propagation in the underwater realm, have lead to remarkable advances in sonar technology in the last years.The work on hand is a sum of knowledge of several authors who contributed in various aspects of sonar technology. This book intends to give a broad overview of the advances in sonar technology of the last years that resulted from the research effort of the authors in both sonar systems and their applications. It is intended for scientist and engineers from a variety of backgrounds and even those that never had contact with sonar technology before will find an easy introduction with the topics and principles exposed here
Applications of aerospace technology to petroleum exploration. Volume 2: Appendices
Participants in the investigation of problem areas in oil exploration are listed and the data acquisition methods used to determine categories to be studied are described. Specific aerospace techniques applicable to the tasks identified are explained and their costs evaluated
Applications of aerospace technology to petroleum exploration. Volume 1: Efforts and results
The feasibility of applying aerospace techniques to help solve significant problems in petroleum exploration is studied. Through contacts with petroleum industry and petroleum service industry, important petroleum exploration problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified where possible. Topics selected for investigation include: seismic reflection systems; down-hole acoustic techniques; identification of geological analogies; drilling methods; remote geological sensing; and sea floor imaging and mapping. Specific areas of aerospace technology are applied to 21 concepts formulated from the topics of concern
Imaging and counting of targets with a high resolution multibeam sonar
Includes abstract.Includes bibliographical references (p. 113-116).This dissertation pertains to the development of an imaging and counting system for a high resolution multibeam sonar. A mathematical model for the operation of the multibeam sonar is derived. The computational model is developed into a simulator for the multibeam sonar in MATLAB
The development and testing of a parametric SONAR system for use in sediment classification and the detection of buried objects
This thesis describes the work carried out in the development and testing of
parametric sonar systems for application in the fields of seabed sediment
characterisation and classification, and the detection of seabed embedded objects.
Parametric sonar systems offer a number of advantages over conventional sonar
systems. This is especially true of the conflicting requirements of both seabed
delineation and penetration required for a practical sub-seabed profiling system.
Echoes from sub-bottom layers vary in strength dependent on both the boundary
acoustic reflectivity and the absorption characteristics of the layer above.
Absorption effects are usually frequency dependent, allowing better penetration to
lower frequency signals. [Continues.
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