I have no idea why it was chosen. I was wondering this myself as I was lifted up 20 ft in the air on a forklift change the lens. The grid was configured manually. We laid out 3 plastic sheets over the machine table with 10"x10" squares. We took a picture and manually dragged points on a grid over the software to match the grid on the table. Then the scale and offset and stuff had to be adjusted. The software was somewhat crude. Once you took a calibration picture, it overrode the original and there was no way to make a backup and as I.said before all the scaling and.offset information was input into a configuration file that was almost entirely written in German.