Generation of a high resolution grid of gravity anomalies by inversion of altimetric data from Geosat, Topex/Poseidon, ERS1/2 and Jason-1 in the Azores region
joao manuel calvao rodrigues(1)
University of Lisbon, faculty of sciences,
Rua Eduardo Coelho 42, r/c,
Stacked data from Geosat, Topex/Poseidon, ERS-2 and Jason-1 are used to define a precise reference frame of satellite tracks, where data with very dense coverage from geodetic missions of Geosat (18 months)and ERS-1 (10 months) are adjusted, allowing a very detailled recovery of the marine gravity field.
A remove restore procedure is used to obtain residual sea surface heights by removing the low and high frequencies (the global geopotencial model EGM96 is used as reference field and the effect of the topography/bathymetry is computed using the RTM correction with the local accurate bathymetric model AZDTM98 and the global model JGM95E.
A validation procedure is applied using a least squares colocation, followed by a grid generation of residual geoid undulations, that are inverted using an efficient method based on Fast Fourier Transfor to obtain residual gravity anomalies.
After adding the contributions to the gravity field from the global model and from the topography/bathymetry, the results are compared with adjusted gravity data obtained from gravimetric surveys.