Differences in log T_eff (top panel), log g (middle panel), and metallicity (bottom panel) between the ROBGrid values and the benchmark values, as a function of log T_eff. Some of the cooler benchmark stars are also analysed by ROBGrid (see Sect. 4.1). GIRAFFE values are shown as red circles, UVES values as blue plus signs. Typical 1σ uncertainties are indicated on the plot (two for log T_eff, representative of cooler stars and of the hottest ones). The blue lines are linear fits to the averaged GIRAFFE + UVES values. These fits are used to correct all ROBGrid log g and metallicity values in the homogenisation phase. The Pearson correlation coefficient (ρ) is also shown in each panel.