Mosaic of edge-on maps of the median radial velocity, Ṽ_R, of thegiant sample. Each map corresponds to a slice of 15 degrees in azimuth: [−30, −15] (top left), [−15, 0] (top right), [0, +15] (bottom left), and [+15, +30] degrees (bottom right). The Sun is represented by a black dot at X = −8.34 kpc and Y = 0 kpc. The Galactic centre is located on the left side. The iso-velocity contours Ṽ _R = 0 km s^-1 are pointed out as black lines. The numbers of stars used to produce the maps are given in the lower left corners.