SEQUENTIAL UPDATING OF PROJECTIVE AND AFFINE STRUCTURE-FROM-MOTION

A structure from motion algorithm is described which recovers structur e and camera position, module a projective ambiguity. Camera calibrati on is not required, and camera parameters such as focal length can be altered freely during motion. The structure is updated sequentially ov er an image sequence, in contrast to schemes which employ a batch proc ess. A specialisation of the algorithm to recover structure and camera position module an affine transformation is described, together with a method to periodically update the affine coordinate frame to prevent drift over time. We describe the constraint used to obtain this speci alisation. Structure is recovered from image corners detected and matc hed automatically and reliably in real image sequences. Results are sh own for reference objects and indoor environments, and accuracy of rec overed structure is fully evaluated and compared for a number of recon struction schemes. A specific application of the work is demonstrated- affine structure is used to compute free space maps enabling navigatio n through unstructured environments and avoidance of obstacles. The pa th planning involves only affine constructions.