Upper panel: comparison of | Z |-distance distribution between the observations towards the Carina line-of-sight and the Besançon model. Middle panel: metallicity versus distance above the Galactic plane for both the observed stars (orange filled circles) and simulated stars from the Besançon model. Lower panel: derived metallicity gradients. The purple plus signs indicate the results obtained from the Besançon model, assuming zero errors on position and metallicity.