Abstract. This article aims to explain how Ptolemy could have constructed a
map of the Pontus Euxinus (Black Sea), as described in his Geography, under the
assumption that his sources were similar to those that have come down to us.
The method employed is based on the comparison of Ptolemy's data with
corresponding information from other ancient sources, revealing the most
conspicuous similarities and differences between them. Three types of
information are considered as possible “constituent elements” of Ptolemy's
map: latitudes, coastline lengths, and straight-line distances. It is argued
that the latitudes Ptolemy used for the key points determining the overall shape of
the Pontus (Byzantium, Trapezus, the mouth of the Borysthenes and the
Cimmerian Bosporus, the mouth of the Tanais, etc.) were most likely
inherited from earlier geographers (Eratosthenes, Hipparchus, and Marinus).
In exactly the same way, Ptolemy's data on the circumference of the Pontus
and the length of the coastal stretches between the key points (from the
Thracian Bosporus to Cape Karambis, Sinope, Trapezus, and the mouth of the
Phasis, etc.) closely correlate with the corresponding estimates reported by
other geographers (Eratosthenes, Artemidorus, Strabo, Pliny, Arrian, and
Pseudo-Arrian), which implies that Ptolemy drew on similar coastline length
information. The shortening of Ptolemy's west coast of the Pontus (from the
Thracian Bosporus to the mouth of the Borysthenes) relative to the
corresponding distances reported by other sources is explained by his
underestimation of the circumference of the Earth. The lengthening of
Ptolemy's north-east Pontus coast (from the Cimmerian Bosporus to the mouth
of the Phasis) can, in part, be accounted for by his attempt to incorporate
the straight-line distances across the open sea reported by Pliny. Overall,
Ptolemy's configuration of the Black Sea can be satisfactorily explained as
a result of fitting contradictory pieces of information together that were inherited
from earlier geographical traditions.
Processing and assimilation of observation data for the hydrodynamics model of the Black Sea and the Sea of Azov
