T–T scatter plot between the ratio E(B−V) /N_H and the gas column density N_H for the two-dimensional projection of the E(B−V) map of Green et al. (2015) (red diamonds) and the GNILC E(B−V) map (blue diamonds) in the high-latitude region of the sky defined in Fig. 10. Each point is the average of E(B−V) /N_H values in a bin of N_H. The bin size varies such that there is always the same number of samples per bin.