Typically most rips have built in calibration tools that enable you to plot them, and an interface that enables you to enter the measurements.
Certainly all Global Graphics / Harlequin RIPS do.
Like Al, am happy to help, but need to better understand what you are looking for and how big you need the squares to be...
Some folks use the P2P target found here, but not for plates:
P2P25xa G7 Calibration Target | IDEAlliance
click on the link "P2P25xa G7 Calibration Target"
Michael Jahn - Slightly used PDF Evangelist
Simi Valley California