1. A position location system including a marking means, the marking means being defined along a path and including a pattern, the pattern comprising an irregular sequence of contiguous spacings, each spacing having a dimension selected from a predetermined set of non-equal dimensions, a cell being defined as a group of a predetermined number of adjacent spacings, the sequence of spacings being arranged whereby any cell within the sequence uniquely locates an associated region of the marking means; pointing means adapted for relative movement adjacent the path of the marking means, the pointing means including means for identifying marking means cells and means for computing the position of the pointing means along the marking means path.