Marine gravity field recovery by combining satellite altimetry and shipborne gravimetry

The approximation of the gravity field in the Newfoundland Sea area off the
east coast of Canada is carried out. Geoid heights, geoid gradients, gravity anomalies
and deflections of the vertical are predicted by combining altimeter data from the
Geosat and ERS-1 Geodetic Missions (GMs) and shipborne gravity data, using both
spectral and collocation techniques. The computed geoid heights are compared with
corresponding TOPEX altimeter Sea Surface Heights (SSHs) and the differences show
an accuracy close to 3 cm in terms of standard deviation (sd). The predicted gravity
anomalies are compared with gravity anomalies from global marine gravity data banks
and the differences are at the level of 4 mGal ( 1 sigma) . Deflections of the vertical are
computed by inverting gravity anomalies and SSHs.The results are intercompared and
found to agree at the level of O.6” -1”(1 sigma).Finally, conclusions are drawn on the
usefulness of each data type and the effectiveness of each processing method.