What is a characteristic feature of the beam of an echo-sounder?

The characteristic feature of the beam of an echo-sounder is that it has a beam width. This beam width refers to the angle at which the sound waves emitted by the echo-sounder spread out as they travel through the water. It is essential for determining the area of seafloor that can be sampled at any given moment. A wide beam width allows for a larger area to be covered, which can be particularly useful in gathering data over uneven or varied underwater terrains.

Understanding beam width is fundamental in hydrographic surveying because it affects the resolution and detail of the data collected. If the beam is too wide, it might not adequately delineate features or obstacles on the seafloor, while a narrower beam could provide more precise information but cover less area. This balance is crucial for effective mapping and surveying tasks.

While the other options present attributes that echo-sounders might possess, they do not encapsulate the defining feature of the beam itself in terms of its physical operation. For instance, the idea that it has a consistent length is misleading because the effective length of the beam can change based on the frequency and environment. Operating at a single frequency is not accurate since modern echo-sounders often operate across multiple frequencies to gain better resolution