Galactic longitude vs. Galactic latitude map of the A _[3.6] /A_Ks extinction coefficient assuming A_J/A_Ks = 2.86 as long as longitudinal and latitudinal distribution of A_λ/A_Ks (λ equals to 3.6, 4.5, 5.8 and 8.0 μm). a) the distribution of A_λ/A_Ks as function of the Galactic longitude. Different colors denotes different wavelengths, the zero line stands for fixed A_J/A_Ks, and the black line indicates the data from Gao et al. (2009). b) The map of the A _[3.6] /A_Ks extinction coefficient, the x-axis denotes the Galactic longitude, the y-axis the Galactic latitude. c) The same as a), but for the Galactic latitude.