Groma (surveying)

The groma (as standardized in the imperial Latin, sometimes croma, or gruma in the literature of the republican times)[1] was a surveying instrument used in the Roman Empire.

Liddell & Scott,[4] "gnoma" is a form) was used, although in multiple sources the Greek term is used to designate the central point of a camp or town.

[8] There were apparently no improvements to groma introduced in Roman times: all writers on the subject clearly assumed the perfect familiarity of a reader with the tool.

[12] The pivoting bracket on the top of the staff was suggested in the 1912 reconstruction by Adolf Schulten and confirmed by Matteo Della Corte [it] soon afterwards.

[15] The archeologists rejecting the bracket suggest that the staff was slightly angled to permit sighting without the pole obscuring the view.

The setup works on the level ground or gentle slopes; the details of a survey crossing a steep-sided valley are not clear.