The metropolitan multi-beam bathymetry is a representation of the submerged part of the surface of the coastal strip. The seabed is represented with a very dense 3D point cloud with X, Y and Z coordinates. It is measured with a multi-beam echosounder, and provides very detailed data that can represent submerged elements of relatively small dimensions (even less than a meter).

The metropolitan topobathymetric elevation model is a representation of the surface of the coastal strip, both the emerged part (dry beach) and the submerged part, up to an approximate depth of between 15 and 20 meters. The depth is represented with a regular grid of 1 meter pixel size. The emerged part is measured with topography methods, the first meters of the submerged part are measured with a single-beam echosounder and the rest is measured with a multi-beam echosounder, which provides very detailed data of the seabed.