Page 414 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

(c)
FIGURE 15.17
Plot of echo returns digitized to profile bottom
(a)
Pencil-shaped beam for profiling sonar applications
(b)
Pencil beam scans on vertical plane for bottom profiling
Transmit pulse
15.2 Sonar types and interpretation 407
Conical beam
A profiling sonar (a) beam depicted, (b) beam scanning of bottom, and (c) display generation of beam scan.
The electrically scanning sonar can either be a spaced steerable array, a multibeam sonar, or a focused array:
• A steerable array involves separate point sources timed to produce a dipole beam. The time spacing of the pulses allows the beam axis to be steered due to additive pulse fronts.
• The multibeam sonar system is normally fixed with a nominal beam width of no more than

• The focused array and acoustic lens sonar technologies are both incredible technologies that focus the acoustic beams onto a localized point at very high frequencies, generating near picture quality images with a high frame rate. More on this technology is detailed at Section 15.2.5.2 below.
180 . The single sonar pulse is generated with multiple high directivity index receivers discriminating the backscatter return over its entire beam width to produce an image of the area under investigation.