The agrimensor (surveyor) played an indispensable role in defining where an edifice could be built, which then permitted the construction plan to be made. He would measure the distances, assess the elevations, and define the axes. For measurement operations in the field, he had sophisticated sight and level instruments such as the chorobate, the groma, and the dioptra, but he also used simpler measurement tools like the ruler and the cord, which is considered to be the ancestor of the tape measure. We know these tools thanks to representations of them on tombstones, and in reliefs and paintings, mosaics and texts.
Vitruvius gives us a description of the chorobate, and Hero of Alexandria, a Greek engineer from the first century CE described the dioptra.
Drawing © Jean-Pierre Adam
