Left: distribution function of the difference between the angles of brightness structures in the dust emission map derived from the Hessian (θ) and inertia (θ_I) analysis. This comparison between the two independent algorithms provides the uncertainty of the Hessian angles that is smaller than the dispersion between the Hessian and polarization angles (Sect. 6). Right: the standard deviation of the difference between the Hessian and inertia angles (θ − θ_I) computed within bins of .