Page 408 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

15.1 Sonar basics 401
Sonar
Sonar
Sonar reflectivity Depicted on sonar display
FIGURE 15.12
Corner
Sonar picture of an underwater rectangular room.
15.1.12 Single- versus multibeam
Active imaging or profiling sonar systems generally fall into three basic categories:
1. Multibeam
2. Mechanically or side-scanning sonar (single beam) 3. Single-beam directional sonar
Single-beam sonars are simply one pulse with one reception on a single receiving element. The single-beam mechanically scanning system comprises the lion’s share of ROV-mounted sonar sys- tems currently on the market today due to their simplicity as well as their reduced cost.
Multibeam sonar systems, on the other hand, transmit one wide pulse and receive the backscat- ter on a large number of receiving elements. Accurate sensing of the delays in sound arrival between elements enables the sonar to distinguish the direction of the received sound, in order to build up a detailed profile of the area being insonified.