Distribution of the stars of the second catalogue in C1-C2 space, where C1 and C2 are the first two principal components in the dereddened centred reduced (Gcr, G_Bcr, G_Rcr, Jcr, Hcr, and Kcr) space and carry 99.9% of the variance. The colour scale refers to the logarithm of the target number. The red line shows the average displacement of a star due to a 1 mag absorption in the visible. Top: before the inter-calibration. Bottom: after the inter-calibration (see Sect. 3.6).