I am approaching to the Oxford Buildings dataset which contains already computed SIFT descriptors from affine detected keypoint locations.
Usually SIFT detector provides to its detected keypoints with scale and orientation information.
In the case of affine keypoints is clear that they don't have a single scale parameter but three corresponding to the ellipse (the affine covariant region) they belong to, but what about orientation, do they have any? if not can I say it is zero?
