ABSTRACT
Radar altimeter data from GEOSAT have made it possible to resolve undulations of the marine geoid as short as 10 to 20 km with a precision of 1 to 2 cm. This is possible if the relative undulations of the sea surface along the satellite tracks are studied, instead of the sea surface height relative to the reference ellipsoid. In order to obtain sufficient data coverage, altimeter data from SEASAT and GEOS-3 have been combined with GEOSAT data. This chapter describes the prospective trends of the Seychelles Platform in the Indian Ocean are examined in relation to the short-wavelength undulations of the sea surface when bathymetric and isostatic effects have been removed. At passive margins, where the water depth increases from less than 200 m on the shelf to several kilometers in the deep ocean, the marine geoid will show a depression of several meters when going from the continent to the deep ocean.
