What issue arises when using an SBES beam sounder on a slope?

When employing a Single Beam Echo Sounder (SBES) on a slope, the most pertinent issue that arises is the lengthening or shortening of the return beam. This phenomenon occurs due to the angle of incidence and the geometry of the slope.

As the sound pulse travels from the transducer to the seafloor and back, its traveling distance can be affected by the slope's angle. When the bottom is sloped away from the transducer, the return path can appear longer, leading to a shallower depth measurement than actual. Conversely, when the seafloor slopes towards the transducer, the return beam may be shorter, which can cause an overestimation of depth. This effect can lead to erroneous data collection, making accurate charting and assessment of underwater topography challenging.

Other options present potential issues related to equipment operation or performance, but they do not directly connect to the specific problems associated with measuring depth on a sloped terrain using an SBES. Thus, the changes in depth measurements due to slope angles create significant challenges in the hydrographic survey process.