1. A method for determining height parameters that describe a dynamically varying height of an ambulatory subject based on video analysis of the subject, comprising: acquiring a sequence of images that collectively captures the gait of the subject; measuring a dynamically varying height function of the subject based on an analysis of the varying height of the subject in the sequence of images; and fitting the dynamically varying height function of the subject to a model that describes varying height, wherein the height parameters correspond to parameters used in the model.