Left: galactic plane distribution of 6.7 GHz methanol masers seen from the NGP overlaid on an artist impression of the Milky Way (R. Hurt: NASA/JPLCaltech/SSC). The spiral structure was constructed following Wainscoat et al. (1992) and the central molecular ring or 3 kpc arms (Green et al. 2011) was indicated, but it is not part of the model. The simulated spatial maser distribution is presented in Sect. 2.2. The plot also includes the intrinsic peak luminosity for each source as the point size following the luminosity function described in Sect. 2.5. In this figure, the Galaxy rotates clockwise. Bottom right: tangential velocity distribution as a function of Galactocentric distance for the simulated 6.7 GHz methanol masers. It also displays the rotation curve, dΘ / dR = −0.2km s^-1 kpc^-1. Top right: radial distribution of the 6.7 GHz methanol masers for our model is also shown. Table 1 presents a summary of the distributions used.