Distributions of relative uncertainties and the uncertainties of the sky location of the events in the simulated catalogue: Upper: distribution of relative uncertainties on the total masses in the catalogue of SMBBH mergers detected by LISA in 5 yr. Solid lines are for default LISA and dashed lines are for 5 Gm arm length. Middle: same as the upper panel, but on the relative uncertainties on the luminosity distances. Lower: same as the upper two panels, but on uncertainties of the sky location (deg²).