Suppose we have two rulers $\mathcal{L}_1$ and $\mathcal{L}_2$ -i.e. sets of parallel segments, separated by a unity distance-. Each segment is linked to an integer number $n \in \mathbb{Z}$.
We can easily measure the distance when both rules are parallel, by taking the distance between the zeros -depicted as red segments-.
One ruler suffer an (small) angular deviation, but I am still forced to calculate an estimate of that distance. How should I calculate or redefine that distance?.
In the parallel case, the distance is the length of the smallest projection following a perpendicular direction.
In the angular deviated case, the distance could be the length of some projection following the green lines directions. But this is only an intuitive guess without any support or justification.
