A gravimetric geoid computation and comparison with GPS results in northern Andalusia (Spain)

Two new GPS surveys have been carried out to check the accuracy of an exist ing gravimetric geoid in a test area located in northern Andalusia (Spain). The fast collocation method and the remove-restore procedure have been use d for the computation of the quasigeoid model. The Spanish height system is based on orthometric heights, so the gravimetrically determined quasigeoid has been transformed to a geoid model and then compared to geoid undulatio ns provided by GPS and levelling at benchmarks belonging to the Spanish fir st-order levelling network. The discrepancies between the gravimetric solut ion and GPS/levelling undulations amount to +/-2 cm for one survey and FS c m for another after fitting a plane to the geoid model.