They use secret code names like 'x' and 'y' and refer to themselves as' unknowns', but we have determined they belong to a common denominator of the axis of medieval with coordinates in every.

A system of coordinates in which a point is located by its distance and direction (Angle) from a fixed point on a reference line (called the polar axis).

According to measuring the coordinates of each span of long span double arched bridge, the arch axis for every span is determined.