Page 402 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

15.1 Sonar basics 395
Barge
FIGURE 15.8
Mechanically scanning sonar viewing barge with scalloped lines from side lobe backscatter.
targets insonified. There are a vast number and category of active sonar products on the market to fit various applications (with the technology advancing daily). Any number of these technologies is available for mounting on ROV equipment for delivery to the work site.
15.1.8 Terminology
The following provides an explanation of the basic terms used to describe sonar techniques:
• Angle of incidence: The angle at which a sound reflects upon a surface (in degrees). Example: If a flashlight is shone on a mirror, the light will reflect directly back to the flashlight if there is a zero angle of incidence, reflected 90 with a 45 angle of incidence, etc. The same principle applies to a sound reflector.
• Beam forming: The principle of forming the sound propagation wave to provide the desired data from the wave front.
• Color: The different colors used to represent the varying echo return strengths.
• Echo: The reflected sound wave.
• Echo return: The time required for the echo to return to the source of the sound.
• Pulse width: The width of a sound propagation wave (in feet, meters, or microseconds)
generated from some source. This factor has an influence on the quality of the image generated
by the sonar receiver.
• Target: The object requiring characterization.
• Target strength (TS): A measure of the reflectivity of the target to an active sonar signal.
• Reflectivity: The ability of a material to reflect sound energy.