Structure-from-motion algorithms based on matched point-like features under orthographic projection are explored, for use in analysing image motion from small rigid moving objects. For two-frame analysis, closed-from n-point algorithms are devised that minimise image-plane positional errors. The bas-relief ambiguity is shown to exist for arbitrary object rotations. The algorithm is applied to real images, and good estimates of the projection of the axis of rotation onto the image-plane are obtained.