Comparison of polarity centres identified by shifting the magnetic field maps (previous algorithm) and shifting the search mask (updated algorithm) for AR 11072. Left column: feature locations from the previous algorithm (black) and the updated algorithm (grey) in the x and y directions of the following polarity (x_f, y_f, top two rows) and leading polarity (x_l, y_l, bottom two rows). Right column: difference between the previous and updated algorithm. The grey shaded regions indicate the uncertainty in the data (also given by σ) from averaging every fourth image of TI+02 datacube of AR 11072 and finding the feature (as shown for AR 11075 in Schunker et al. 2019, Appendix D). The differences can be outside of the uncertainties in the data. AR 11072 is an active region in the southern hemisphere. The active region is shown with the sign of the polarities inverted and the map reversed in the latitudinal direction, as used in the statistical analysis.