Geoid studies in the north-east atlantic (azores-portugal)

摘要

During the past two years several studies concerning geoid computation have been done in the north-east Atlantic region between the Azores Archipelago and Portuguese mainland. The gravimetric geoid has been derived from gravity data, and uses the remove-restore procedure with the central step performed by least squares collocation method. Several comparisons between different geoid solutions were made considering two different DTMs (ETOPO5U and local bathymetric data) and different resolutions of the reference surface of the Residual Terrain Model computation. For the original ETOPO5U data the differences between altimeter and gravimetric geoid has a standard deviation of 0.24m with an amplitude of 1.26 m. It was found that ETOPO5U must be shifted 5' West in order to get better residual anomalies (lower variance). This new file was merged with local bathymetric data and edited to produce a new DTM. A second solution was obtained with this merged DTM, and the differences between altimeter and gravimetric geoid has a standard deviation of 0.18m and an amplitude of 1.25 m. The differences between this new gravimetric geoid and the altimetric surface approximate the Sea Surface Topography in this area very well.