Multibeam Sonar Theory of Operation

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Multibeam Sonar Theory of Operation Detection Processing and Range Calculations Figure Chapter 4 - -21: Beam Patterns of the Nearest Steered Beams Amplitude-Weighted Time of Arrival (TOA) Computation The amplitudes of the echoes A B associated with each time slice are collected and ordered sequentially in time. Since there are many time slices per ping, the collection can be quite large. The sequence of amplitudes represents a record of the echoes received from θ B during the ping cycle, including noise events, true bottom echoes, and reverberation events. A collection of amplitudes A B for beam angle θ B is represented schematically in Figure Chapter 4 - -22. Copyright © 2000 L-3 Communications SeaBeam Instruments Page 4-23 No portion of this document may be reproduced without the expressed written permission of L-3 Communications SeaBeam Instruments
Detection Processing and Range Calculations Multibeam Sonar Theory of Operation Figure Chapter 4 - -22: Interpolated Amplitudes for a Single Beam in All Time Slices Time sequences such as this can be examined by the operator if the beam with angle θ B is the selected beam. The selected beam, which is chosen from the SEA BEAM 2100 menu (see Chapter 9 of the SEA BEAM 2100 Operator’s Manual), corresponds to one of the beam angles used in WMT processing. The sequence of amplitudes of the selected beam is represented on a logarithmic scale. It allows the operator to examine the “cleanliness” of acoustic returns— if beams contain well-defined bottom echoes, if there is much noise present, if there is are secondary echoes, and so forth. For each beam, an associated start gate and stop gate are specified as times (either by the SEA BEAM 2100 operator or computed automatically). Essentially, the start gate tells the SEA BEAM 2100 to only process time slices that occur after it, and the stop gate tells it to only process time slices that occur before it. All other time slices are ignored when computing WMT TOAs. In Figure Chapter 4 - -23 start and stop gates are applied to the sequence of echo events for the beam angle θ B . Figure Chapter 4 - -23: Eliminating Time Slices Outside the Gates Page 4-24 Copyright © 2000 L-3 Communications SeaBeam Instruments No portion of this document may be reproduced without the expressed written permission of L-3 Communications SeaBeam Instruments
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Multibeam Sonar Theory of Operation

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