Galactic location of the open clusters projected to the Galactic plane. Open clusters with spectroscopic data are highlighted with larger symbols. The Galactic centre is located at (X/Y) = (0/0) kpc and the Sun at (X/Y) = (8/0) kpc. Galactic longitudes in degrees are indicated for better orientation. Furthermore, we show the spiral arm model by Bobylev & Bajkova (2014) as solid lines. The spiral arms from the inner to the outer area are Scutum-Crux, Carina-Sagittarius, Perseus, and Cygnus.