Automated PIL identification in a photospheric longitudinal magnetogram of NOAA 12253, observed by SDO/HMI on 2 January 2015. The identified PILs in the region are further characterized as “moderate” (yellow contours) and “strong” (red contours). The difference between “strong” and “moderate” PILs relies on the absolute value of the gradient of the vertical magnetic field (>40 G/pixel and >16 G/pixel, respectively) and the strength of the horizontal field (>120 G and >100 G, respectively). Parts of the PIL that are not highlighted in color are below one or both thresholds and are considered as “weak”. The algorithm used is the FLARECAST PIL identification code, accessible as described in Appendix A.2.