how measure the dynamic resolution of displacement vectors?

I am wondering how can I measure the dynamic resolution of motion vectors? for example, in the attached images, you can see the ground truth and the results of two approaches to block matching. I did use the mean absolute error and root mean square error to measure the error between the ground truth and the estimated motion.

I also need to measure the dynamic resolution of each method as you can see the magnitude of the motion vector is changing in each image. Can I use the signal to noise ratio (PSNR)? any help would appreciate.