Groma surveying

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Chain und Groma: By Carolus Stephanus and Johannes Liebhaltus, Straßburg 1579.
Groma

The Groma or gruma was a Roman surveying instrument.[1] It comprised a vertical staff with horizontal cross-pieces mounted at right-angles on a bracket. Each cross piece had a plumb line hanging vertically at each end. It was used to survey straight lines and right-angles, thence squares or rectangles.[2] The same name was given to:

  • the center of any new military camp, i.e. the point from which was traced the regular grid by using the groma instrument
  • the center of a new town, from which the gromatici (surveyors) began to lay out cardo and decumanus grid, with a plough and a pair of oxen

The groma surveying instrument may have originated from Mesopotamia, and may have been imported by the Greeks in the 4th century BC. Subsequently, it was brought to Rome by the Etruscans and named cranema or ferramentum.[3]

Notes

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External links

  • Cesare Rossi, Marco Ceccarelli, Michela Cigola, The groma, the surveyor's cross and the chorobates. In-depht notes on the design of the old instruments and their use. La Groma, lo Squadro agrimensorio e il corobate. Note di approfondimento su progettazione e funzionalità di antiche strumentazioni, in Disegnare Idee Immagini, anno XXII n. 42/2011; pp. 22-33. ISBN 978-88-492-2248-7, ISSN IT 1123-924
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