Motion estimation is significant in the applications of video image compression

super-resolution reconstruction

mosaic

and target detection

and so on. In this letter

we present an improved algorithm for the problem of highly accurate sub-pixel global motion estimation

which introduces an optimal filter for computing image gradient

and also adopts the method of combining upsampling with paraboloid fitting gradient cross-correlation. Experimental results show that the proposed algorithm can not only achieve good robustness to the influence of noise

but can also improve the accuracy of motion estimation significantly.