1. A camera movement correction apparatus for use in a system which detects the position of a sporting projectile within a scene, the apparatus comprising: an interface operable to receive a first and second image of the scene captured by a camera; a reference marker determiner operable to determine the position of a reference marker within the first and second image of the scene, the reference marker being static within the scene; a difference determination device operable to determine the difference between the position of the reference marker in the first and second image of the scene; and a corrective transformer operable to apply a corrective transform to the second image on the basis of said determined difference.