1. An apparatus for identifying at least one discrete moving object within a series of video images, said apparatus comprising: an image recording device that stores a time series of video images; and an image analysis device that is configured to execute a program of machine-executable instructions to identify at least one moving object in said time series of video images, wherein said program includes the steps of: identifying a plurality of feature point tracks in said time series of video images, wherein for each video image of said time series of video images, all feature points belonging to a same feature point track are located within a polygon of a predefined size; and calculating a trajectory similarity factor for each pair of feature point tracks said plurality of feature point tracks, wherein each trajectory similarity factor is a measure of a maximum distance between a pair of feature point tracks.