Reconstruction of Roman measuring tool – groma

Reconstruction of the Roman measuring tool – the so-called groma – which is located in the museum of the Roman theater in Lisbon. The tool was used to measure straight lines and right angles and was the main tool used by Roman geodesists to build roads, buildings or divide agricultural land.

This device was known for its accuracy already in Mesopotamia and Greece in the 4th century BCE. The tool came to Rome from Etruria and had the name cranema or ferramentum. The device allowed to survey straight lines andright angles and for projecting all construction works.

Roman geodesists were called gromatici or agrimesores.