Kiel diagram for different ranges of Galactocentric radii and vertical elevations from the midplane. The 2D histogram shows the relative distribution (made with a kernel density estimator) of the transformed GALAH data in each spatial bin. The grey iso-density contours are plotted at the 1, 5, 10, 30, 50, and 70% of the maximum density for the stars from APOGEE-2. In each bin, N_G and N_A refer to the number of stars from the GALAH and APOGEE catalogues, respectively. The horizontal dashed red lines show the upper and lower limit for the selection of giant stars used in Sect. 4.