Satellite Altimetry

The seafloor is not a smooth and uniform place. It has as many topographical features as on land. From the Continental Shelf through to the continental slope, the continental rise, the abyssal plane, mid oceanic ridges, seamounts, guyouts and trenches the seafloor varies and plays a vital role in the dynamics of the planet. For this reason, the seafloor and its features are extensively studied. The topography of the ocean floor is given the name Bathymetry.

In order to map and study the bathymetry, several methods are used. The earliest method of doing this was to get depth measurements at different points in the sea and plot submarine contour lines using them. This was a tedious process. With the development of technology new methods such as, echosounding, multibeam methods and seismic refraction and reflection methods are used today. The latest method of mapping the seafloor is Satellite Altimetry.

Like the name suggests this method uses satellites in orbit to map the seafloor. These satellites measure the slight differences of the sea level, and not the depth. Then how can it be used to map the seafloor? The way it's done is, the slight changes in sea level actually represent the topography of the seafloor. The undisturbed surface of the ocean represents the geoid - the gravitational equipotential surface. This means that at seamounts and ridges where there is a higher mass and thus higher gravitation, The sea-level would be higher and places such as trenches where the relatively lower mass lessens the gravitation, the sea level would be lower. Therefore by measuring the differences in sea level, the bathymetric features can be identified. This bathymetric data is used to plot bathymetric maps as shown below

bathymetry of the the indian ocean