be executed by any suitable general purpose microprocessor such that in one embodiment the apparatus can be a conventional personal computer pc such as a standard desktop or laptop computer with an attached monitor the computer can be connected to an imaging device such as a digital video camera or can input a video file captured by a separate imaging device and transferred to the computer alternatively the apparatus can be a dedicated device the invention can also be embodied as a computer program stored on any suitable computer readable storage medium such as a solid state computer memory a hard drive or a removable disc shaped medium in which information is stored magnetically optically or magneto optically the computer program comprises computer executable code that when executed on a computer system causes the computer system to perform a method embodying the invention referring to fig2 a and 2 b the apparatus comprises a moving platform 10 e g a vehicle such as an aeroplane or satellite with an imaging device 20 that captures a sequence of still images preferably the movement of the platform indicated by the arrow 40 is constant and is known either by design or by measurement and is a pure translation with no rotation component preferably the motion of the platform is parallel to an approximately flat background 50 such as the ground or sea at a fixed height h the imaging device 20 has a constant field of view 30 with respect to the moving platform 10 sequential images are captured with the imaging.