1. A method of enhancing the visibility of at least one feature of an image superimposed on a real world scene containing said feature, the method comprising: acquiring image data of said real world scene including said at least one feature using sensing means; processing the image data to identify changes in adjacent data points corresponding to a boundary of the at least one image feature; generating modified image data corresponding to the boundary of the at least one image feature; and displaying in real time an outline image corresponding to the modified image data superimposed on the boundary of said at least one feature in the real world scene.