Two dimensional projections of the median μ_b, LSR for the three mock catalogues, namely the flat-disc null hypothesis (left column) and the Sine Lopsided warp disc (middle column) and the S Lopsided warp disc (right column). The size of the bins is 0.16 kpc × 0.32 kpc. We mark the Sun position with a star. The grey solid lines show the Galactocentric azimuths: 135°, 180°, and 225°, and the black dotted lines show circles at different Galactocentric radii, R = 8, 10, 12, 14, and 16 kpc.