1. An apparatus for identifying a height of a feature of a moving object from 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 a height of a group of salient points of a moving object, wherein said program includes the steps of: identifying a group of salient point pixels in a time series of video images, wherein said group of salient point pixels corresponds to a group of salient points having a common estimated height range and located on a moving object; generating a plurality of time series of homographied images by performing homography transformations on said time series of video images at at least two homography reference planes having different heights and located above, and spaced from, a surface on which said moving object travels, wherein each time series among said plurality of time series corresponds to a homography reference plane that is different from any other of said at least two homography reference planes; generating a plurality of sets of inter-salient-point pixel distances by generating, for each selected homography reference plane among said at least two homography reference planes, a set of inter-salient-point pixel distances that are determined by measuring inter-salient-point pixel distances between at least one pair of salient point pixels in said group of salient point pixels for a time series among said plurality of time series of homographied images corresponding to said selected homography plane; measuring variations among inter-salient-point pixel distances for each set of inter-salient-point pixel distances among said plurality of sets of inter-salient-point pixel distances; and determining a height of said group of salient points from a surface on which said moving object travels based on comparison of said measured variations.