The cognomen gromaticus means "agrimensor" or "surveyor" and derives from groma, one of their common tools in antiquity.
Its application to Hyginus derives from the Codex Arcerianus,[1] whose copy of the Corpus Agrimensorum Romanorum reads in part exp[licit] Kygini gromatici constitutio feliciter ("The establishment of Kyginus the Surveyor explains well...").
His only extant work is De Constitutione [Limitum] ("On the Establishment [of Boundaries]")[3] in the Corpus Agrimensorum Romanorum ("Body of Roman Surveying"), a collection compiled in Late Antiquity.
Notably, in his discussion of the establishment of the decumanus and cardo—the main east–west and north–south thoroughfares in most Roman towns—Hyginus is decidedly in favour of the construction of the decumanus using a gnomon (sundial) and compares this method with other less precise methods such as using the location of sunrise and sunset.
The text has some connection with a passage included in Bubnov's Geometria Incerti Auctori ("Geometric Works of Unknown Authors").