High-resolution geoid and sea-floor topography
computed from altimeter data
of ERS-1 and Geosat Geodetic Missions

Abstract

Combining altimeter data of the ERS-1 and Geosat Geodetic Missions, we have produced high-resolution (1/32 deg x 1/32 deg) grids of the mean sea surface (a close approximation of the marine geoid) and seafloor topography. ERS-1 and Geosat data were updated with the latest orbits and tide models and where possible with improved environmental corrections. In addition, benefiting of the highly accurate data of the Topex-Poseidon altimetry mission, crossover minimizations between ERS-1/Geosat and Topex-Poseidon sea surface heights were performed to further reduce the residual orbit error. The mean sea surface height was computed by combining the ERS-1 and Geosat data sets by bilinear interpolation as well as by the collocation method. This high-resolution mean sea surface (close to the marine geoid) filtered out from wavelengths > 500 km, was then used as input in a global 2-D spectral inversion to compute the seafloor topography in the waveband 15-500 km. Isostatic compensation of the topography was taken into account through the lithospheric flexure model. Increase of the elastic plate thickness versus age was assumed to follow an isotherm of the lithospheric half-space cooling model. The inverted bathymetry was completed by wavelengths longer than 500 km using the long-wavelength signal of ETOPO-5. Validation of the solution has been performed through comparison with in situ bathymetry data of the NGDC.