Comparison between Altimetric and Gravimetric Geoid in the South — West Mediterranean Basin
The processing of altimetric data collected by the Topex-Poseidon satellite on the Western Mediterranean sea, based on the Barrick-85 model, permitted the extraction of the instantaneous sea surface height. The analysis of 76 passes distributed over 8 orbital arcs, after correction of the disturbing effects (troposphere, ionosphere,…), the reduction of the instantaneous measurements and elimination of the weak periodic variable phenomena, allowed us to give a mean altimetric profile.
The processing of the mean arcs on the crossing points by the least squares method allowed us to get a mean level on the western Mediterranean sea with a precision of a centimeter. The results confirm the dominance of an East-West current along the Algerian coast and the existence of localized eddies off the North African coasts (Bernard & al, 1993).
The sea surface obtained from Topex data were compared to the global geoid deducted from the OSU91A potential model. The metric difference obtained shows insufficient adequacy of the global solutions for geodetic applications. The comparison of the solution above with a gravimetric geoid provided by the collocation method (using Gravsoft software and a set of BGI free air gravity anomalies surrounding the region) near the Algerian coasts, improves the results appreciably and shows the importance and the influence of the inshore quality data.
The introduction of exhaustive and precise altimetric data, and of gravimetric measurements with sufficient density, will permit to define a more precise altimetric surface of the geoid by the intergration of the existing tidegauge measurements.
KeywordsAltimetric Data Orbital Error Gravimetric Geoid Altimetric Measurement North African Coast
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- N. Arent, K.R. Koch, 1992. Method for obtaining geoid undulations from satellite altimetry data by a quasi geostrophic model of sea surface topography. Manuscripta Geodaetica 17.Google Scholar
- R. Barzaghi, F. Sanso, 1992. Altimetry rank deficiency in crossover adjustment — Manuscripta Geodaetica 17.Google Scholar
- S. Benahmed Daho, 1996. Détermination du géoïde gravimétrique par la méthode de collocation. Magister thesis, CNTS Arzew.Google Scholar
- J.F. Bernard, F. Barlier, 1993. First Seasat altimeter data analysis on the western Mediterranean sea. JGR 88.Google Scholar
- S. Bhaskaran, G.W. Rosborough, 1993. Computation of regional mean sea surface altimeter data — Manuscripta Geodaetica 18.Google Scholar
- P. Bonnefond, 1994. Méthode géométrique de trajectographie par arcs courts. Doctoral thesis; CERGA Grasse.Google Scholar
- M.I. Kariche, 1997. Traitement des données du satellite Topex-Poseidon, Comparaison avec un modèle global de potentiel — Magister thesis — CNTS Arzew.Google Scholar
- Y. Ming Wang, R.H. Rapp, 1992. The determination of a one year mean sea surface height track from Geosat altimeter data and ocean variability implication. — Bull. Geod 66.Google Scholar