A Fourier Approach to Cloud Motion Estimation

Abstract

A Fourier phase difference technique for cloud motion estimation from pairs of pictures is described. This technique makes use of the phase of the cross-spectral density; it allows motion estimates to be made for individual spatial frequencies, which are related to cloud pattern dimensions. Results obtained using this technique are presented and are compared with the results of a Fourier-domain cross-correlation scheme, using both artificial and real cloud data. It is concluded that the phase difference technique is relatively sensitive to the presence of mixtures of motions, changes in cloud shape and edge effects. Under these circumstances, the cross-correlation scheme yields a more reliable estimate of cloud motion.