Oceanography

Remote sensors

Sea level can also be measured from satellites. An altimeter measures the distance between the satellite and the sea surface. If the satellite position is accurately known this results in a sea level measurement. Modern altimeters have reached an accuracy of better than 5cm. The global coverage provided by satellites allows the verification of global tide models. When the tides are substracted, the measurements give information about the shape of the sea surfaces and, through application of the principle of geostrophy, the large scale oceanic circulation.