This probably a dumb question, but…
In football, when the ball is close to the first down point and it’s too hard to call out on the field, they drag the 10 yard posts out onto the field.
Now, here’s my question: Do the referees just run out there, hoping to run as perpendicular to the football field as they can, and measure it? It seems like a tiny bit of tug in either direction could throw it off.
Or, probably more likely, but I don’t know for sure - at the end of every down, do they round off the ball position so that it’s always exactly on one specific yard line? In that case, do they drag the poles out, align the rear one with the tick mark for the official start yard line, and take it from there? In that case, it would seem that you’d be able to judge whether the ball was over just by comparing it to the 10th tick mark away from the line of scrimmage.