Groma

The groma is a surveying instrument, first Etruscan, then Roman.

It was used by the agrimensor (Roman surveyor) to set out perpendiculars over long distances so that towns and camps were always "square".

The groma consists of a pole topped by a horizontal cross (at right angles). Each end of the cross carries a plumb line. By sighting along the lines in both directions, one can simply set out perpendiculars, or perfect squares with 4 gromas.

This solid oak groma is fitted with a steel point for planting it in the ground, and 4 fixing rings to hold it to the ground and keep it in position.

All the joints, of the arm and of the cross, are bronze.

The cross of the original gromas was generally solid bronze, which made them very heavy and very costly objects.