Schematic representation of the spiral arm model of the MW as proposed in this work. The Sun is marked with a yellow dot and the Galactic center with a red cross. The dashed lines are arm extrapolations; for the Perseus arm, we changed the pitch angle of this inner segment to ψ = 0° in order to connect it with the Norma arm, and for the Sct-Cen arm the pitch angle was set to ψ = 3° to connect it with the other extreme of the bar.