Computed and observed ocean topography - A comparison

The Goddard Space Flight Center's latest Gravity Earth Model, GEM-8, was used to construct a static sea surface. Such a surface corresponds to the surface of an ocean without the time-varying effects of atmospheric pressure, surface wind friction, tides, and currents. It conforms to a surface dictated by the earth's gravitational and rotational forces. The sea surface model is the result of analyzing more than 500,000 satellite observations together with about 1600 5 deg x 5 deg and about 38,000 1 deg x 1 deg surface gravity anomalies. Preliminary comparisons between the computed and measured sea surface topography indicate that they agree quite well and differ by less than 1 m in many places including the Atlantic test area. Sea-surface features such as undulations caused by trenches and ridges are clearly and accurately detectable. The use of altimeter data for orbit computation reduces the uncertainty of the spacecraft height and thus the errors of the sea-surface topography.