H I column density in the solar neighbourhood determined via Eq. (10) at different Galactic latitudes b, based on the LAB data. H I emission from high- and intermediate-velocity clouds has been masked. The regions QI (squares) and QIV (triangles) are shown separately. The mean column density is shown by circles. Values at | b | > 45° (empty symbols) are strongly contaminated by the Local Bubble. Using only data at 10°< | b | < 45° (filled symbols) we infer Σ_{HI, ⊙} = 5.3 ± 0.5 M_⊙ pc^-2 (accounting for the H I opacity, but not correcting for He).