1. An apparatus for mapping a gaze point of a subject on a scene image to a gaze point in a reference image, wherein said scene image and said reference image have been taken by a camera from a different position, said apparatus comprising: A module for executing a feature detection algorithm on said reference image to identify a plurality of characteristic features and their locations in said reference image; a module for executing said feature detection algorithm on said scene image to re-identify said plurality of characteristic features and their locations in said scene image; a module for determining a point transfer mapping that transforms point positions between said scene image and said reference image based on the locations of said plurality of characteristic features detected in said reference image and said scene image; a module for using said point transfer mapping to map a gaze point which has been determined in said scene image to its corresponding point in said reference image.