SUMMARY
Continuous gravity observations performed in the last few years, both at Mt. Etna and Stromboli, have promptedthe need to improve the tidal analysis in order to acquire the best corrected data for the detection of volcanorelated signals. On Mt. Etna, the sites are very close to each other and the expected tidal factor differences arenegligible. It is thus useful to unify the tidal analysis results of the different data sets in a unique tidal model.This tidal model, which can be independently confirmed by a modeling of the tidal parameters based on the elasticresponse of the Earth to tidal forces and the computation of the ocean tides effects on gravity, is very usefulfor the precise tidal gravity prediction required by absolute or relative discrete gravity measurements. Thechange in time of the gravimeters sensitivity is also an important issue to be checked since it affects not onlythe results of tidal analysis but also the accuracy of the observed gravity changes. Conversely, if a good tidalmodel is available, the sensitivity variations can be accurately reconstructed so as to retune observed tidalrecords with the synthetic tide, since the tidal parameters are assumed to be constant at a given location.