"Sonar echoes." . . "Sounding." . . . "The evaluation of dual beam echo sounders in hydrographic surveying"@en . . . "The Evaluation of dual beam echo sounders in hydrographic surveying"@en . . . . . . "The Evaluation of Dual Beam Echo Sounders in Hydrographic Surveying"@en . . . . . . . . . . . . . . . . . . . . . . . "A limited area hydrographic survey was conducted in shallow water, using a launch equipped to sound concurrently with three beam widths, in order to evaluate the benefits of dual beam echo sounders. The narrow beam echo sounder has become commonplace in hydrographic surveying. This has reduced the bottom area insonified by the echo sounder's beam, which decreases the probability of detecting navigational hazards. The dual beam echo sounder, equipped with a narrow and wide beam, sounding concurrently, represents a relatively inexpensive means to increase the detection capabilities, while preserving the narrow beam operation. The wide beams detected significant peaks that were absent on the narrow beam trace. The wider hyperbolic returns of the wide beams served to emphasize the narrow beam returns over features with little horizontal extent. The narrow versus wide beam depth differences over feature peaks were found useful in isolating the peak's apex. (Author)."@en . . . "Side looking sonar." . . "Underwater object locators." . . "Hazards." . . "Shallow water." . . "Resolution." . . "Narrow beams(radiation)" . . . . "Accuracy." . . "Ocean bottom topography." . . "Hydrology, Limnology and Potamology." . . "Navigation charts." . . "Theses." . . "Hydrographic surveying." . . "NAVAL POSTGRADUATE SCHOOL MONTEREY CA." . . "Echo ranging." . . "Acoustic beams." . . "Acoustic Detection and Detectors." . . "Depth finding." . . "Mapping." . .