Number of lightning to earth in Italy

After twelve years of operation, the lightning location system installed in Italy by CESI s.p.a. (named CESI SIRF®) collected over fifteen millions of lightning data. The present paper shows the methodology applied to these data, in order to evaluate the ground flash density (N_g) in Italy, under the supervision of the Italian Standards (CEI). A critical step was to take into account all data losses due to sensor temporary failures and to the intrinsic network efficiency. The choice of the calculation step for the geographic grid kept into account both influence on the Ng representation and Standards needs. The resulting Ng map will appear in the new CEI publication on ground flash density.