Top: location of the stellar sample of carbon stars around the Sun. The Sun is placed at (X, Y) = (0, 0). Stars are taken from the surveys by Chen et al. (2007) and Chen & Yang (2012). Blue dots show normal N-type carbon stars; red dots represent J-type stars, and cyan dots show stars of unknown type according to Chen & Yang (2012) that are labelled possible carbon stars in SIMBAD. Bottom: distribution above or below the Galactic plane vs. galactocentric distance. The Sun is at R = 8.34 kpc. The typical uncertainty in the (X, Y, Z) coordinates is ±20 pc, and it is ±50 pc for the galactocentric distance (see text).