Levelling rod and level determination apparatus and method e.g. for geodetic applications

The levelling rod (1) has a plurality of bars (11) therealong and serving to express a position along the levelling rod, each bar having a width (Wx) taken from a set of width values. The pitch between two adjacent bars (11) is a variable value, and selected from a set of predetermined pitch values (p1, p2), such that the position along the levelling rod is expressed in terms of the following two parameters: i) the width (Wx) of at least one bar, and ii) at least one pitch value separating adjacent bars. In an embodiment, the level has a set of coded height bar blocks provided with a constant length along the length measuring direction of a level to digitally indicate heights. Each bar block comprises 3 bar symbols which are aligned at two different pitches. The width dimensions of the bar symbols, with the selected constant pitch values determines that any 3 adjacent bar symbols in the longitudinal direction of the levelling staff is different from any other 3 adjacent bar symbols chosen from any other portion of the barcode scale. The invention also relates to a level determination apparatus specifically adapated for that levelling bar, and to a method of using of that apparatus.