This paper presents two new eigenstructure-based algorithms for estima
ting the motion parameters of a rigid object from scaled orthographic
projections. The approach requires neither point correspondences betwe
en time frames nor between projections at each time. 2D statistics fro
m projections are utilized to recover 3D statistics, which are used fo
r motion estimation. This results in significant speed-up compared to
the approach where point correspondences need to be found. The first a
lgorithm is suitable for general point configuration and requires thre
e scaled orthographic projections at each time frame. The second algor
ithm is suitable for planar configuration of data points and requires
only two orthographic projections at each time instant. Results of sim
ulated and real image experiments demonstrate the performance and effi
ciency of the algorithms, as well as showing their limitations.