Enhanced Parallax Correction (EPC) works with calculating two yields at the same time and uses the variance in between to ensure the highest accuracy on each scan.

​

Read more about Parallax from wikipedia;

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances.