Bathymetry n. : The art or science of sounding, or measuring depths in the sea.

Example:


Taxonomy
measurements, bathymetry data, measure, soundings, surveys, seafloor topography, free encyclopedia, depths, map, beams, bathymetric, bathymetric maps, remote sensing, LADAR, sounder, single-beam, MBES, sensors.

Defination from the web:
bathymetry (and altimetry). Data from the National Geophysical Data Center's TerrainBase Digital Terrain Model. ... For deep water bathymetry, this is typically Mean Sea Level (MSL) but most data used for nautical charting is referenced to Mean Lower Low Water ...