Study of underwater depth of lake or ocean floors. In other words, It is the underwater equivalent to hypsometry or topography.

• A. Hypsometry
• B. Bathymetry
• C. Photogrammetry
• D. Loxodrome

Answer: (B)

Bathymetry is the measurement of how deep the ocean or a lake is and the mapping of the seafloor’s shape. It is the underwater counterpart to hypsometry or topography, which describes elevations on land relative to sea level. Depth data come from sonar systems, like single-beam and multibeam echosounders, and can also involve satellite methods in broader, indirect ways. Bathymetric maps reveal depths, contours, and underwater features, which are essential for navigation and marine science. Hypsometry focuses on land elevations, photogrammetry uses photographs to measure distances or create maps (not specifically about underwater depth), and a loxodrome is a navigational line of constant bearing, not a method for mapping seabed depth.