3.2.2.5.5. Bathymetry

Bathymetry is the measurement of the ocean depths. Although is has no direct use for altimetry data processing, it can be useful for shallow water (since ocean altimetry is not at its best there), or to compare with some ocean features, like currents.
Bathymetry can be computed using among other things altimetry sea surface heights (via the geoid) measurement (see Applications: Geophysics: Bathymetry).

Bathymetry and topography given in the Envisat data. This map is drawn using the Basic Radar Altimetry Toolbox

The (I)GDRs provide a parameter bathymetry that gives the ocean depth or land elevation of the data point. Ocean depths have negative values, and land elevations have positive values. This parameter is given to allow users to make their own "cut" for ocean depth. It is not a direct computation from the data within the same dataset.