This paper is a continuation of research within my texts Cp2 and Cp3. In his Geographike Hyphegesis, Ptolemy sets down the length of the oikoumene attributable to Marinus the Tyrian. In so doing we find two major pointers which can be utilised to ascertain how Marinus calculated this length.

Firstly, as already evidenced by research in texts Es1, Es2 and Cp3, the Eratosthian Stade of c157.5 metres is used by both Marinus and Ptolemy with their mapping of at least India.

Secondly, in the text of Ptolemy we read that the two eastern distance measures, to and from the Stone Tower are itinerary measures, and thus it is possible to confirm that Marinus has used the same methodology as Eratosthenes of Cyrene to calculate and thus establish his oikoumene; Itinerary measures.

12 A4 pages and 7 full colour diagram maps

The map of Marinus the Tyrian is in fact the map used by Claudius Ptolemy but drawn on a different graticule. A simple investigation of the text of Claudius Ptolemy reveals that fact. Also indicated, despite the protestations by Ptolemy concerning the length of the oikoumene given by Marinus, is the fact that Ptolemy actually uses the same length, although he tries to hide the fact, to determine his oikoumene of only 180 degrees.

16 A4 pages and 13 full colour diagram maps