I own a CNC machine (Shapeoko 3 XXL) which I use to make projects that require good 90° angles, and I have been through several steps of improvement/calibration of the machine that are described in the documentation. However the rails of the machine's frame are nearly impossible to "square" below a deviation of about 1mm/meter or 2mm/meter. Besides that, the rails may be slightly different and some unknown factors can play a role an reduce precision of the machine. I suppose however that repeatability is far better than actual precision.
So I have though of something: why not measure the difference between the CAD and the result on several points on the xy plane of the machine and apply a correction to recalculate the CAD model, or even better, just the Gcode?
It makes so much sense that I thought I would easily find a computer program that already has been designed to apply such corrections on the Gcode, but I didn't fin any result on any search engine. Have you ever heard of such a project?