Codex Arcerianus ‘A’ contains many Latin texts and particularly works by Hyginus Gromaticus. One would perhaps assume that with a surname taken from the Roman surveyor’s instrument, “The Groma”, any text written by him concerning survey techniques would be correct and to the point.
I have already shown (in text Rm4) that is not what we find when reading these texts. It would appear he was more a mathematician and geometrician than a surveyor, and wrote accordingly.
This text (part A) concerns the technique of establishing N S E &W using a gnomon and three shadow lines from the Sun’s rays. It is a mixture of practical work, knocking in a post or gnomon, and drawing work. As such, it would be extremely difficult to combine and carry out in the field.
Thus we see a theoretical concept transformed into a supposed practical concept, and failing. When in the field surveying alignments for a new Territorium or similar, it is best to keep all techniques as simple as possible, using the minimum of equipment.
The second part of the text (part B) examines the actual physical process of surveying the main points, Decumanus and Kardo Maximus, and discusses the knowledge required by an Agrimensor.

The text is 7 A4 pages and there are 14 diagrams, some of which are full colour. The paper is presented with the diagrams within the text for easier comprehension of the survey technique involved.