Metallicity measurements at different latitudes reported by previous studies: red triangles correspond to (l,b) = (+1, − 4) and (0, −6) fields from Zoccali et al. (2008), blue diamonds are from Johnson et al. (2013) and correspond to (l, b) = (8.5, 9), (−5.5, −7) and (−4, −9), the inverted yellow triangles correspond to (l, b) = (0, −7.5) and (0, −10) from Ness et al. (2013), the cyan circle corresponds to (0, −8) from Johnson et al. (2011), and the grey squares are from this work. The lines show several metallicity gradients obtained by the authors in the legend. The lines and points share the same colour if they are part of the same work.