Modelled (left) and observed (middle) absolute Hess diagrams of the the stars in common between RAVE and Gaia DR2. The right panel displays their relative ratio. The sample belongs to the solar cylinder of 300 pc radius and 1 kpc height below the midplane with stars selected in the sky area of the TGAS×RAVE sample (see Sect. 2.1 and Fig. 1). The thick disc is included in the modelling. Model and data are both smoothed with a window of 0.04 × 0.2 mag² (2 × 2 bins in (G_BP − G_RP, M_G)).