Of paths and places: the origin of Ptolemy’s Geography

2018

Hist. Geo Space. Sci.

Abstract. The lengths of the coastlines in Ptolemy's Geography are compared with the corresponding values transmitted by other ancient sources, presumably based on some lost periploi (literally "voyages around or circumnavigations", a genre of ancient geographical literature describing coastal itineraries). The comparison reveals a remarkable agreement between them, suggesting that Ptolemy relied much more heavily on these or similar periploi than it used to be thought. Additionally, a possible impact of Ptolemy's erroneous estimate of the circumference of the Earth is investigated. It is argued that this error resulted in two interrelated distortions of the coastal outlines in Ptolemy's Geography. First, the north-south stretches of the coast that were tied to particular latitudes are shown compressed relative to the distances recorded in other sources in roughly the same proportion to which Ptolemy's circumference of the Earth is underestimated relative to the true value. Second, in several cases this compression is compensated by a proportional stretching of the adjacent east-west coastal segments. In particular, these findings suggest a simple explanation for the strange shape of the Caspian Sea in Ptolemy's Geography.

Section: Periploi Among the Sources Of Ptolemy's Geographymentioning

confidence: 99%

“…Numerous researchers have developed a wide array of different methodological approaches to studying its nature and genesis (e.g. Isaksen, 2011Isaksen, , 2013Marx, 2011Marx, , 2016Heß, 2016;Shcheglov, 2017;Graßhoff et al, 2017;Arnaud, 2017;Defaux, 2017). One of the main approaches is a comparison with other ancient sources.…”

Section: Introductionmentioning

confidence: 99%

The length of coastlines in Ptolemy'sGeographyand in ancient periploi

2018

Hist. Geo Space. Sci.

“…Recent studies devoted to the Geography, as different as they are, largely share a common methodological stance: they attempt to analyse Ptolemy's data via comparison with the modern map and, in particular, to reconstruct his sources and methods through the distortions he made (see e.g. Livieratos et al, 2008;Kleineberg et al, 2010;Mintz, 2011;Marx and Kleineberg, 2012;Rinner, 2013;Defaux, 2017;Abshire et al, 2016;Graßhoff et al, 2017). However, it would be methodologically more correct, before approaching Ptolemy from the viewpoint of modern knowledge, to consider his data in the context of his own time, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Correspondingly, the east-west spacing of places situated north of this parallel is progressively expanded the further north they are. ranean and the Red seas; and Rinner (2013) and Graßhoff et al (2017) on Asia Minor.…”

Section: Introductionmentioning

confidence: 99%

The configuration of the Pontus Euxinus in Ptolemy's Geography

2020

Hist. Geo Space. Sci.

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.

“… Schwartz 1893, 265-266, 273; Cuntz 1923, 110; Knapp 1996, 30-35; Mintz 2011, XXI;Graßhoff, Rinner, Mittenhuber, 2017;Arnaud 2017; ср. попытку обосновать широкое использование Птолемеем астрономических измерений широт: Santoro 2017.10 Вопросы, связанные с Марином Тирским, главным источником Птолемея, подробно рассматривались нами в других публикациях и поэтому сейчас полностью выносятся за скобки; см., например, Щеглов 2014.11 Схожее определение возможных источников Птолемея см., например:Graßhoff, Rinner, Mittenhuber 2017, 493-494;Defaux 2017, 177-210.…”

unclassified

The structure of space in Ptolemy’s Geography: methodological challenges in georeferencing ancient toponyms

2019

Schole

In this paper I would like to draw attention to several features inherent to Ptolemy’s Geography that limit the effectiveness of different mathematical approaches to georeferencing (i.e. locating within the modern coordinate system) its unidentified places. Out of the 6,300 coordinate points listed in Ptolemy’s Geography, approximately 50% still don’t have recognized identifications on the modern map. This makes the Geography a real bonanza for researchers developing different methods to translate Ptolemy’s coordinates into the modern ones. Most of these methods can be effective only insofar as Ptolemy’s Geography is regarded as an example of what David Woodward called “equipollent-coordinate space” where “every place in the system is of equal geometric significance.” This kind of space is supposed to be as continuous and homogeneous as the space of the modern maps is. My central thesis is that Ptolemy’s space was closer to what Woodward has called “route-enhancing space,” in which “the routes are endowed with the importance of direct observation,” hiding behind the mask of the “equipollent” one. This hidden nature of Ptolemy’s space manifests itself in two interrelated aspects: it was discrete and hierarchically organized. On the one hand, there are reasons to suppose that most points on Ptolemy’s map were originally located not in relation to their nearest neighbors, but rather in relation to a few distant reference points. On the other hand, Ptolemy tended to distribute all places more evenly throughout the entire space they occupy and to round their coordinates as much as possible. These features of Ptolemy’s method result in that, even if he tried to follow his sources most closely, each separate point on his map could have been displaced relative to its original neighborhood. The displacements are often so significant and unpredictable that they cannot be adequately described by a single continuous function. Mathematical methods remain, of course, an important tool for studying Ptolemy’s Geography and, in particular, for georeferencing its unidentified places. However, like any instrument, these methods have limited effectiveness. The specific features of Ptolemy’s method pointed out in the present paper can contribute to our understanding of how these methods can be improved and enhanced.