Spatial distribution and metallicity of the RR Lyrae sample represented in a Galactocentric reference frame. r_GC and z denote the radial distance to the GC and the vertical distance with regard to the Galactic midplane x − y, respectively. The Cartesian Galactocentric coordinates and the radial distances to the GC have been summarised by the median plus minus the difference in absolute value between the median and the 84th and 16th percentile of the posterior samples of Eqs. (19) and 20.