bathymetrie

Bathymetry, also known as bathymétrie in French, is the measurement of the depth of water bodies and the mapping of the underwater terrain. It describes the shape and features of the seabed, including slopes, ridges, canyons, and trenches. The resulting data are essential for navigation, coastal management, and marine science.

Depth measurements are primarily acquired with sonar systems. A single-beam echo sounder sends a single acoustic pulse to the seafloor, while a multibeam echo sounder emits numerous beams to produce high-resolution, gridded bathymetric data. Bathymetric surveys can be conducted with hull-mounted, towed, or unmanned platforms, and in shallow water with airborne LiDAR.

Data are referenced to a vertical datum and corrected for tides, water level, and vessel motion. Key corrections include the speed of sound in water, which varies with temperature, salinity, and depth, usually determined from sound velocity profiles. The measured depths are processed into digital elevation models and harbor charts.

Applications include nautical charting and safe navigation, dredging and port design, coastal and marine habitat mapping, sediment transport studies, and the routing of submarine cables and pipelines. Bathymetry is also used in oceanography to study seafloor processes and in geological research.

Limitations include measurement errors from water-column refraction and motion, resolution limits set by sensor configuration, and data gaps in complex terrain. Satellite-based bathymetry offers broad coverage but lower accuracy and is restricted to clear, shallow water.