Radial profiles of the ratio between the column density in the filamentary structures and the total column density (N_H). From top to bottom, the panels correspond to each Galactic quadrant and to the whole Galactic longitude range. The colors indicate the Galactic longitude of the tiles. The vertical dotted line indicates the radius of the solar orbit. The solid line in the bottom panel indicates the mean values of in 1-kpc R_gal bins.