Comparator Hypotheses

What's measured in yards? We thought of many things, including concrete and fabric (forget it). This doen't seem to be a surveying device, since the calibrations would be in feet or meters, if anything, but probably unitless.

Thus, we came to a device for aiming artilliary, an idea that has gotten much support from our friends who have seen the machine or talked with us about it. It makes sense: enter the deviation of a strike from the target, yards left or right, yards too close or too far, and the machine calculates a correction.