Recovering Deflections of Vertical from A Tangent Plane of Gridded Geoidal Heights from Altimetry

To improve the space resolutions of vertical deflections and gravity anomaly recovering from altimetry data, a new method for computing vertical deflections is presented. At first, we eliminate the influence of sea surface topography from the mean sea surface height of altimetry data along ground tracks, and regard the results as geoidal heights. The data coordinates are then transformed into new Cartesian coordinates, which consist of a osculating tangent plane and a normal of the reference ellipsoid. Then, we fit a osculating tangent plane of the local geoid using a least-squares approach by minimizing the squared summation of the total distance between the discrete points and the fitting plane; this is to determinate the mean value of each component of the vertical deflections. An experiment was made in the area of the South China Sea. The comparisons between the vertical deflections determined by this method and those by other methods show that the precision of this method agrees well with those from other methods on 5′x5′ grid.