“…In one implementation, equally spaced laser beams are directed perpendicularly to the pendulum's plane of motion, with electric sensors on its opposite side. Design specifics of this and related position measurement methods may be found in [9] and the references therein. Since we may know the response of this stroboscopic measuring system without knowing the technical details of its optical and electrical dynamics, we shall assume that the value space Val( p) of pointer quantity p (calibrated in angular or length units) of p is a subset of discrete points in C. This means that since the pendulum's positions are measured at discrete time instants stroboscopically with limited accuracy, we need a spatial discretization of the circle group C of positions, specified by the discrete set C ε = d f εN ∩ C = {0, ε, 2ε, · · · } of possible angular pendulum positions on a circle, where ε > 0 is a fixed discretization parameter, chosen in arc or length units, e.g., one arc second or one millimeter.…”