The absolute position of a target object point is determined using a series of images of the scene with overlapping fields of view captured by a camera in positions arranged in at least two dimensions across the scene and position data representing the absolute positions of the camera on capture of the respective images. The images are analyzed to identify sets of image points corresponding to common object points in the scene. A bundle adjustment is performed on the sets of image points that estimates parameters representing the positions of the object points relative to the positions of the camera associated with each image, but without using input orientation data representing the orientation of the camera. The absolute position of the target object point is derived on the basis of the results of the bundle adjustment and the absolute positions of the camera represented by the position data.