1. A method of measuring similarity with respect to moving object trajectories, said method comprising: inputting first and second moving object trajectories, each trajectory being defined by at least two spatial dimensions and a temporal dimension, each trajectory including at least two defining points; defining at least one segment with respect to each trajectory, each segment being defined between two defining points; matching at least one segment from the first trajectory with at least one segment from the second trajectory; computing a spatial distance between the at least one segment from the first trajectory and the at least one segment from the second trajectory; computing a temporal distance between the at least one segment from the first trajectory and the at least one segment from the second trajectory; and combining the spatial distance and temporal distance to provide a measure of a spatio-temporal distance between the at least one segment from the first trajectory and the at least one segment from the second trajectory.