1. An image processing method, comprising: capturing image data from a sequence of images of a scene from different but repeatable viewpoints, capturing said image data with a mobile platform traveling over a repeatable path; associating captured images with a respective viewpoint identification based on a position of the mobile platform when the captured image was captured; tracking a region of interest in the sequence of images; performing an eigenspace projection for respective images of the sequence to calculate respective points in the eigenspace projection; and comparing a calculated point to a point previously obtained for a reference image for a same viewpoint; wherein a change between a calculated point and a corresponding previously obtained point indicates a change in image content of the region of interest between a corresponding captured image and a corresponding reference image for the substantially same viewpoint.