The list of immunes (soldiers who were excused mundane chores on account of a specialized skill; see AW XI.2) drawn up by the emperor Commodus’ Praetorian Prefect Taruttienus Paternus begins with mensores or ‘surveyors’ (Digest 50.6.7). The late writer Vegetius records that, while it was the mensores “who measure out the plots in camps in which the soldiers set up their tents”, it was actually men called metatores “who go ahead and choose the site for a camp” (Epitome of Military Science 2.7.7 and 9). However, he also claims that it was the responsibility of men called agrimensores “to calculate the measurements of the area in order to accommodate the size of the army” (Epitome 3.8.5). Thus, he seems to suggest that there were three different types of military surveyor.
A fourth individual emerges from an incidental remark in Hyginus’ , where we read that the camp is laid out by means of a surveying instrument called a , and that “those who practise this skill” (12.2). Curiously, this is the only occurrence of the term in all of Latin literature. And, although Hyginus does not mention either the or the , he writes that, if cavalry are relegated to the rear of a Roman camp, “this is undoubtedly a sign of the ’s inexperience” (46.2). The implications are twofold: first, cavalry need to be able to take the field promptly and without hindrance, and second (which is more relevant to our theme), the men who laid out the army camps were called .
