Bathymetry is the science and technology of measuring or estimating depth. Its aim is to determine the relief of the deep or coastal ocean.

Precise knowledge of bathymetry is essential for a large number of applications. In the case of hydrographic services and more particularly Shom, the safety aspects of navigation largely motivate the concern for measurement accuracy. Furthermore, bathymetry supports a large number of other activities such as knowledge and monitoring of the marine environment, hydrodynamic modeling, integrated management of marine spaces or underwater navigation, to name but just a few.

The Shom mainly uses acoustic techniques (multibeam echosounders) on ships or hydrographic launches, or active optics (airborne lidar) to acquire new bathymetric data. It is not limited to these sources of information alone since it uses satellite information (optical or altimeter) and the digital heritage of its database.