Mean 12 + log(O/H) profiles for all data points (left panels) and those with log Σ(Hα) < 39 in units of log erg s⁻¹ kpc⁻² (right panels) derived using the direct method T_e([SIII]) and the N2 and O3N2 strong-line calibrators from Denicoló et al. (2002) (D), Pettini & Pagel (2004) (PP), and Marino et al. (2013) (M). The standard deviation of the 12 + log(O/H) values are indicated by the shaded regions. A clear increase in mean metallicity is observed with distance when using all HII-based calibrators as well as the N2 and O3N2 indices for both the full dataset and the subset with log Σ(Hα) < 39. When applying the direct method, the metallicity distribution across the ISM appears flat.