Roman Surveying

The groma was the principal surveying instrument of the Roman agrimensores, the land surveyors. The instrument itself was simple in design, crossed arms resting on a bracket and attached to a vertical staff. The four arms each had a cord with a hanging plumb bob. It was designed to survey straight lines and right angles. On the right is a drawing of a replica of a groma now in the Science Museum, London. The original metal parts were found in the Workshop of the surveyor Verus at Pompeii, and are now in the Museo Nazionale, Naples. Click on the plumb bobs or the pointed end of the staff to see photographs of the original parts.

We are fortunate to have the tombstone of a Roman surveyor with a sculpted relief, figure to the left, which depicts certain attributes of his profession. It is the tombstone of Lucius Aebutius Faustus, of the first century B.C. and is in the Museo Civico at Ivrea in Northern Italy.

The stone relief has a Latin inscription which is translated as follows:

Lucius Aebutius Faustus, freedman of Lucius Aebutius, of the tribe of Claudia, surveyor, sevir, erected this monument while still alive for himself and his wife Aria Aucta freedwoman of Quintus Arrius, and their children, and the freedwoman Zepyra.

The component parts of the sculptural relief are the following: In the pediment are a shield and spears. Beneath the inscription is a dismantled groma. Above this are the symbols of a sevir, two fasces and between them a low seat.  

Photo Credits:

• Museo Civico, Ivrea
• Museo Nazionale, Naples
• Science Museum, London

Bibliography:

• O.A.W. Dilke, The Roman Land Surveyors, New York, 1971

• O.A.W. Dilke, "Roman Large-Scale Mapping in the Early Empire," in The History of Cartography, Volume One, Cartography in Prehistoric, Ancient and Medieval Europe and the Mediterranean, J.B. Harley and David Woodward, eds., Chicago, 1987, pp. 212-223.

The Plumb-Bobs of a Groma

These plumb-bobs are examples of what Roman carpenters, bricklayers, and surveyors used to trace vertical lines and to determine horizontal planes. Plumb bobs are usually conical and are either made of bronze or iron.

Descriptions from Top to Bottom:

• Left, H. 4 cm, Diam. 4.7 cm. Bronze Right, H. 4.5 cm, Diam. 6 cm. Bronze
• Left, H. 2.7 cm, Diam. 2.5 cm. Bronze Right, H. 3 cm, Diam. 2.2 cm. Bronze
• Left, H. 5.3 cm, Diam. 4.6 cm. Bronze Right, H. 5 cm, Diam. 3.6 cm. Bronze

• Musei Capitolini, Rome, Italy
• Museo Nazionale, Rome, Italy


• Museo Nazionale, Rome, Italy

The Point of a Groma

The point (to the right), usually made of bronze, was placed on the end of a staff to secure the groma in its position before surveying. It is possible that this example was used either on a groma or on a measuring staff.

Descriptions:

• Diam. 1.5 cm. Bronze

• Museo Nazionale, Naples, Italy