
Initial research in to camera tracking systems can be traced back to two main sources. The first is within the world of astronomy and the other is derived from robotics systems.
Astronomy applies tracking techniques to gain more information about our position in space. As this can only be done relatively, the observation of binocular and monocular images can be used to register distances between stars and planets.
In the area of robotics camera tracking (ego-motion) is employed to help the machine locate it's position in a room, in relationship to static or even moving objects around it. For these systems the feedback time needs to be almost instant. At the moment tracking can be done at speeds as fast as 30Hz [i] and even 10Hz [ii]. Robotics research for tracking dates back to the early eighties. Ten years later it found its way in to the film industry. A very early example of this work can be found in the film "Jurrasic Park" [iii]. Up until this time the director was restricted to simple static camera systems, or to heavy weight motion control systems (such as the one developed by Industrial Light and Magic in the late seventies for the film "Star Wars"). In "Jurrasic Park" the director was allowed to film hand held shots, using small florescent markers on the floor, to aid the computer and its user in replicating the camera motion within the computer's 3D space.
It was from this point onwards that camera tracking was used to seemlessly augment reality with two and three dimensional elements. It could be used to extended traditional effects. Background mattes, for example, can be dynamically added to a scene without having to hand paint changes on every frame [iv]
From film, this technique has found its way on to the small screen. With modern day technology real-time tracking can be used for adding slogans to billboards at live sports events, and it can be used for placing live action performers on to virtual sets [v][vi].
The essential building block for such systems is in acurate feature tracking. Some methods involve pattern recognition patterns based on patterns of colours within a selected area. Others use the detection of motion blur to get a sense of speed and direction [vii]. Many systems depend on edge detection, where the changes in contrast/intensity are used as guides to the shape and position of features[viii][ix].
The future of ego-motion seems to lie in the interactive/games market. Systems have already been developed which can interperate object and even human motions [x]