1. A method of video image motion measurement, comprising: phase plane correlating a current and reference image to produce a correlation surface, and to extract candidate motion vectors between blocks of the current and reference images from the correlation surface; setting a correlation resolution to a sub-block size; shifting sub-blocks of the reference image by candidate motion vectors for corresponding blocks; correlating shifted sub-blocks with sub-blocks of a current image using a sub-block neighborhood to determine valid vector assignments; and employing global motion parameters to assign motion vectors to sub-blocks where correlation fails.