Calibration of screw variation along axis

Is there a tutorial on how to setup lead screw calibration ? Or surface mapping offset etc ? 

I'm getting  service call as soon as i can to laser measure and calibrate my 2 converted machines

I searched but didn't find anything conclusive 

Screw-mapping is done with a compensation file:
Look for "COMP_FILE" here.
linuxcnc.org/docs/stable/html/config/ini...ub:ini:sec:joint-num

You can either tabulate nominal position v actual position, or nominal position v error to nominal.