l_gal, b_gal, r_pc -> Av
Drimmel, Cabrera-Lavers and Lopez-Corredoira, 2003, A&A 409, 205
A three-dimensional Galactic extinction model

Needs: l (gal long), b (gal alt), r (pc)

Ranges: l [0,360]
        b [-90,90]
        r [0,8000]

The calibration is based on the Galactic dust distribution
model of Drimmel & Spergel (2001, ApJ, 556, 181)