Radial, azimuthal, and vertical velocity dispersion (σ_R, σ_φ , and σ_Z) as a function of the Galactocentric radius R. The thin and the thick discs are represented by open squares and filled circles, respectively. The full orange line corresponds to the whole thick disc, while the red and blue dashed lines represent its decomposition into two sub-samples (Fe-rich and Fe-poor). The error bars correspond to the standard deviation of 1000 bootstrapping realisations. The average [Fe/H] and [Mg/Fe] values of each population for the whole R range are marked.