Application of the grid-adapted EVC method to an artificial flow composed of two Lamb–Oseen vortices of opposite orientation superposed by a Gaussian noise signal. Top panel: Rortex map. Bottom panel: G-EVC map. The cardinality s accounts for the number of EVC points which coordinates fall in the same grid cell. The blue circles show the approximate location of the two vortex centers. The regions where R ≠ 0 are outlined by a gray contour in the Rortex map.