(a) Crossing of two reconnection separatrices at a certain distance from the X-point (t = 247, α = 5°), selected via the threshold on |J| and on the scale-integrated PVI, as well as using human labeling (true positive). (b) Crossing of two separatrices close to the X-point of a reconnecting region (t = 247, α = 78°), which is again a true positive. (c) Crossing of two separatrices (t = 247, α = 13°) selected via the threshold method on J and on PVI, but not via human labeling (i.e., false positive). (d–f) Overview of the structures crossed in the 2D box.