Average |B_LOS| in QS areas. The QS areas of the whole FOV are sub-divided into identical tiles. For each tile the mean |B_LOS| is calculated. Histograms of the mean |B_LOS| for tiles with a size corresponding to 77 and 20 Mm are shown in purple and olive, respectively. The red dots mark the mean |B_LOS| values derived for the six major voids (cf. Table 1) as a function of their size (right axis). See Sect. 3.3.2.