Best-fit model parameters l_c as a function of A, derived for the TLS model, across the entire Galactic plane (left panel), in the central (middle panel) and the peripheral regions of the Galactic plane (right panel). The overplotted contours represent the density of pixels, with levels at 100, 300, 800, and 1200 for all the Galactic plane and the central regions, and levels at 50, 100, and 300 for the peripheral regions of the Galactic plane.