Quasi-geoid estimations in South America

A report on quasi-geoid computations in South America, based on the existing gravity data base collected in the framework of the South America Gravity Project (SAGP) is presented. Two estimation methods will be described. One of these is the standard “remove-restore” technique. The gridding of the residual gravity values (i.e. free air gravity anomalies minus the global geopotential model and the terrain effect) has been performed using, with some Refsinements, the GEOGRID program of the GRAVSOFT package (Tscherning et al, 1994) and the residual quasi-geoid signal has been evaluated through the ID FFT approach (Haagmans et al., 1993) which allows a fast and rigorous computation of this component. The second approach is based on ID FFT method applied on mean Helmert’s gravity anomalies, having removed the low frequency components using EGM96 model up to degree 50.