The levelling rod (1) for a level determining apparatus (2) has position indications therealong along expressed by barcode symbols (11, 12). At least some of said barcode symbols are color barcode symbols, the color serving to encode said position indications. The barcode symbols can be organised in first and second blocks (12, 11) of barcode symbols, each providing a position indication, wherein the length (Ls) occupied along the rod (1) by a first block (12) is smaller than the length (Lb) occupied along the rod by a second block (11), the first blocks thereby providing a finer position indication than the second blocks. The first blocks (12) of barcode symbols can be formed of monochrome and color bar code symbols, e.g. just one color barcode symbol and at least one monochrome barcode symbol, while the second blocks (11) can be formed purely of color barcode symbols. The invention also relates to a level determining apparatus specifically adapted for the above rod, and to a method of using that rod.