The Geography (also known as Geographia, Cosmographia, or Geographike Hyphegesis) is Ptolemy's main work besides the Almagest. It is a treatise on cartography and a compilation of what was known about the world's geography in the Roman Empire of the 2nd century. Ptolemy relied mainly on the work of an earlier geographer, Marinos of Tyre, and on gazetteers of the Roman and ancient Persian empire.
Manuscript tradition 
The Geography comprises two parts: Book one, a discussion of the data and of the methods used; and Books 2–5, an atlas. The original work included maps, but due to the difficulties involved in copying them by hand, the original maps have mostly fallen out of the manuscript transmission, with the notable exception of Miniscule 3686. Maps based on the few surviving copies or maps redrawn from the coordinates in the text have been re-added to medieval copies of the work.
Arabic writer al-Mas'udi, while writing around 956, mentioned a colored map of the Geography which had 4530 cities and over 200 mountains. Byzantine monk Maximus Planudes found a copy of the Geography in 1295, and since there were no maps in his copy, he drew his own based on the coordinates found in the text. In 1397 a copy was given to Palla Strozzi in Florence by Emanuel Chrysoloras.
An oldest copy of the work, the 13th-century Codex Seragliensis GI 57 was found in the Topkapı Palace in Istanbul. It was used as the base of a new edition of the work in 2006. This new edition was used to "decode" Ptolemy's coordinates of Books 2 and 3 by an interdisciplinary team of TU Berlin, presented in publications in 2010 and 2012.
Relevant research on Ptolemy's Geography manuscripts and printed editions, concerning the Geography versions coordinates, has been carried out since 1998 by members of the cartography group, school of surveying engineering, at the Aristotle University of Thessaloniki. See, e.g. selective papers in the web journal "e-Perimetron"
Principles of mapping 
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As with the model of the solar system in the Almagest, Ptolemy put all this information into a grand scheme. He assigned coordinates to all the places and geographic features he knew, in a grid that spanned the globe. Latitude was measured from the equator, as it is today, but Ptolemy preferred to express it as the length of the longest day rather than degrees of arc (the length of the midsummer day increases from 12h to 24h as one goes from the equator to the polar circle). He put the meridian of 0 longitude at the most western land he knew, El Hierro (one of the Canary Islands).
Ptolemy also devised and provided instructions on how to create maps both of the whole inhabited world (oikoumenè) and of the Roman provinces. In the second part of the Geographia he provided the necessary topographic lists, and captions for the maps. His oikoumenè spanned 180 degrees of longitude from the Canary islands in the Atlantic Ocean to China, and about 80 degrees of latitude from the Arctic to the East Indies and deep into Africa; Ptolemy was well aware that he knew about only a quarter of the globe.
Maps based on scientific principles had been made since the time of Eratosthenes (3rd century BC), but Ptolemy improved projections. It is known that a world map based on the Geographia was on display in Autun, Gaul in late Roman times.
Medieval Islamic civilization 
Islamic cartographers inherited Ptolemy's Almagest and Geographia in the 9th century which is said to have stimulated an interest in geography and map-making; however, they made almost no direct use of the latter in map-making. Muslim scientists then made many of their own contributions to geography and the earth sciences.
Ptolemy's text reached Italy from Constantinople in about 1400 and was translated into Latin by Jacobus Angelus of Scarparia around 1406. The first printed edition with maps, probably in 1478 in Rome, may also be the first printed book with engraved illustrations. Many editions followed (more often using woodcut in the early days), some following traditional versions of the maps, and others updating them. An edition printed at Ulm in 1482 was the first one printed north of the Alps. Also in 1482, Francesco Berlinghieri printed the first edition in vernacular Italian.
Ptolemy had mapped the whole world from the Fortunatae Insulae (Cape Verde or Canary Islands) eastward to the eastern shore of the Magnus Sinus. This known portion of the world was comprised within 180 degrees. In his extreme east Ptolemy placed Serica (the Land of Silk), the Sinarum Situs (the Port of the Sinae), and the emporium of Cattigara. On the 1489 map of the world by Henricus Martellus, which was based on Ptolemy’s work, Asia terminated in its southeastern point in a cape, the Cape of Cattigara. Cattigara was understood by Ptolemy to be a port on the Sinus Magnus, or Great Gulf, the actual Gulf of Thailand, at eight and a half degrees north of the Equator, on the coast of Cambodia, which is where he located it in his Canon of Famous Cities. It was the easternmost port reached by shipping trading from the Graeco-Roman world to the lands of the Far East. The promontory or cape on which it was situated, the Cape of Cattigara, formed the southeastern point of Asia. In Ptolemy’s later and more well-known Geography, a scribal error was made and Cattigara was located at eight and a half degrees South of the Equator. On Ptolemaic maps, such as that of Martellus, Catigara was located on the easternmost shore of the Mare Indicum, 180 degrees East of the Cape St Vincent at, due to the scribal error, eight and a half degrees South of the Equator.
Catigara is also shown at this location on Martin Waldseemueller’s 1507 world map, which avowedly followed the tradition of Ptolemy. Ptolemy’s information was thereby misinterpreted so that the coast of China, which should have been represented as part of the coast of eastern Asia, was falsely made to represent an eastern shore of the Indian Ocean. As a result, Ptolemy implied more land east of the 180th meridian and an ocean beyond. Marco Polo’s account of his travels in eastern Asia described lands and seaports on an eastern ocean apparently unknown to Ptolemy. Marco Polo’s narrative authorized the extensive additions to the Ptolemaic map shown on the 1492 globe of Martin Behaim. The fact that Ptolemy did not represent an eastern coast of Asia made it admissible for Behaim to extend that continent far to the east. Behaim’s globe placed Marco Polo’s Mangi and Cathay east of Ptolemy’s 180th meridian, and the Great Khan’s capital, Cambaluc (near Beijing), on the 41st parallel of latitude at approximately 233 degrees East. Behaim allowed 60 degrees beyond Ptolemy’s 180 degrees for the mainland of Asia and 30 degrees more to the east coast of Cipangu (Japan). Cipangu and the mainland of Asia were thus placed only 90 and 120 degrees, respectively, west of the Canary Islands.
Christopher Columbus 
Christopher Columbus modified this geography further by using 53⅔ Italian nautical miles as the length of a degree instead of the longer degree of Ptolemy, and by adopting Marinus of Tyre’s longitude of 225 degrees for the east coast of the Magnus Sinus. This resulted in a considerable eastward advancement of the longitudes given by Martin Behaim and other contemporaries of Columbus. By some process Columbus reasoned that the longitudes of eastern Asia and Cipangu respectively were about 270 and 300 degrees east, or 90 and 60 degrees west of the Canary Islands. He said that he had sailed 1100 leagues from the Canaries when he found Cuba in 1492. This was approximately where he thought the coast of eastern Asia would be found. On this basis of calculation he identified Hispaniola with Cipangu, which he had expected to find on the outward voyage at a distance of about 700 leagues from the Canaries. His later voyages resulted in further exploration of Cuba and in the discovery of South and Central America. At first South America, the Mundus Novus (New World) was considered to be a great island of continental proportions; but as a result of his fourth voyage, it was apparently considered to be identical with the great Upper India peninsula (India Superior) represented by Behaim—the Cape of Cattigara. This seems to be the best interpretation of the sketch map made by Alessandro Zorzi on the advice of Bartholomew Columbus (Christopher’s brother) around 1506, which bears an inscription saying that according to the ancient geographer Marinus of Tyre and Christopher Columbus the distance from Cape St Vincent on the coast of Portugal to Cattigara on the peninsula of India Superior was 225 degrees, while according to Ptolemy the same distance was 180 degrees.
See also 
- J. L. Berggren, Alexander Jones; Ptolemy's Geography By Ptolemy, Princeton University Press, 2001 ISBN 0-691-09259-1
- Milanesi, Marica (1996). "A Forgotten Ptolemy: Harley Codex 3686 in the British Library". Imago Mundi (in English) 48: 43-64
- Alfred Stückelberger, Gerd Graßhoff, et al. (eds.), Ptolemaios Handbuch der Geographie (Griechisch-Deutsch) (2006), ISBN 3-7965-2148-7
- Andreas Kleineberg, Christian Marx, Eberhard Knobloch, Dieter Lelgemann, Germania und die Insel Thule. Die Entschlüsselung von Ptolemaios´ „Atlas der Oikumene“. Wissenschaftliche Buchgesellschaft, Darmstadt, 2010, ISBN 978-3-534-23757-9.
- Andreas Kleineberg, Christian Marx, Dieter Lelgemann, Europa in der Geographie des Ptolemaios. Die Entschlüsselung des „Atlas Oikumene“: Zwischen Orkney, Gibraltar und den Dinariden. Wissenschaftliche Buchgesellschaft, Darmstadt, 2010, ISBN 978-3-534-24835-3.
- Christian Marx, Andreas Kleineberg, Die Geographie des Ptolemaios. Geographike Hyphegesis Buch 3: Europa zwischen Newa, Don und Mittelmeer. epubli, Berlin, 2012, ISBN 978-3-8442-2809-0.
- "Geographia (trans. Jacobus Angeli), et al.". Bodleian Library. Retrieved 23 September 2012.
- Emilie Savage-Smith, ed. (2004). Medieval views of the cosmos. Oxford: Bodleian Library, University of Oxford. pp. 61–62. ISBN 1-85124-184-1.
- Stevens, Henry N. (1908), Ptolemy's Geography, A brief account of the Printed Editions down to 1730
- David Landau & Peter Parshall, The Renaissance Print, pp 241-2, Yale, 1996, ISBN 0-300-06883-2
- Dennis Rawlins, "The Ptolemy GEOGRAPHY's Secrets", DIO - The International Journal of Scientific History, Vol. 14, March 2008 [www.dioi.org/bk/de0.pdf].
- See Oc Eo.
- J.W. McCrindle, Ancient India as described by Ptolemy, London, Trubner, 1885, revised edition by Ramachandra Jain, New Delhi, Today & Tomorrow’s Printers & Publishers, 1974, p.204: “By the Great Gulf is meant the Gulf of Siam, together with the sea that stretches beyond it toward China”; Albert Herrmann, “Der Magnus Sinus und Cattigara nach Ptolemaeus”, Comptes Rendus du 15me Congrès International de Géographie, Amsterdam, 1938, Leiden, Brill, 1938, tome II, sect. IV, Géographie Historique et Histoire de la Géographie, pp.123-8.
- Paul Schnabel, „Die Entstehungsgeschichte des kartographischen Erdbildes des Klaudios Ptolemaios“, Sitzungsberichte der Preussischen Akademie der Wissenschaften: Philosophisch-Historische Klasse, Verlag der Akademie der Wissenschaften, Bd.XIV, 1930, S.214-250, n.b. 239-243; cited in Albert Herrmann, “South-Eastern Asia on Ptolemy’s Map”, Research and Progress: Quarterly Review of German Science, vol.V, no.2, March–April 1939, pp.121-127, p.123.
- See Waldseemuller Map
- “Alberico”, vol.IV, c.169, Florence, Biblioteca Nazionale Centrale, Banco Rari 234; Sebastian Crino, "Schizzi cartografici inediti dei primi anni della scoperta dell' America", Rivista marittima, vol. LXIV, no.9, Supplemento, Novembre 1930, p.48, fig.18. Downloadable at: www.henry-davis.com/MAPS/Ren/Ren1/304.1.html
Further reading 
- Berggren, J. Lennart and Jones, Alexander. 2000. Ptolemy's Geography: An Annotated Translation of the Theoretical Chapters. Princeton University Press. Princeton and Oxford. ISBN 0-691-01042-0.
- Cosgrove, Dennis. 2003. Apollo's Eye: A Cartographic Genealogy of the Earth in the Western Imagination. Johns Hopkins University Press. Baltimore and London.
- Stevenson, Edward Luther. Trans. and ed. 1932. Claudius Ptolemy: The Geography. New York Public Library. Reprint: Dover, 1991. This is the only complete English translation of Ptolemy's most famous work. Unfortunately, it is marred by numerous mistakes (see Diller) and the place names are given in Latinised forms, rather than in the original Greek.
- Diller, Aubrey (February 1935). "Review of Stevenson's translation". Isis 22 (2): 533–539. Retrieved 2007-07-15.
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Primary sources 
- Claudii Ptolemaei Geographia, ed. Karl Friedrich August Nobbe, Sumptibus et typis Caroli Tauchnitii, 1843, tom. I (books 1-4); 1845, tom. II (books 5-8); 1845, tom. III (indices). (Greek original).
- (Latin) Geographia Universalis, Basileae : apud Henricum Petrum, mense Martio, Venezia, 1540.
- (Latin) Geographia Cl. Ptolemaei Alexandrini, Venetiis : apud Vincentium Valgrisium, Venezia, 1562.
- Claudii Ptholemaei Alexandrini liber geographiae cum tabulis et universali figura et cum additione locorum quae a recentioribus reperta sunt diligenti cura emendatus et impressus (Latin translation, with updated (16th century) geographical positions).
- Ptolemy's Geography at LacusCurtius (English translation, incomplete)
- Extracts of Ptolemy on the country of the Seres (China) (English translation)
- 1st critical edition of Geography Book 8, by Aubrey Diller
- (Italian)Geografia cioè descrittione vniuersale della terra partita in due volumi..., In Venetia : appresso Gio. Battista et Giorgio Galignani fratelli, 1558.
- (Italian) Geografia di Claudio Tolomeo alessandrino, In Venetia : appresso gli heredi di Melchior Sessa, 1599.
Secondary material 
- Ptolemy the Geographer
- Ptolemy's Geography of Asia - Selected problems of Ptolemy's Geography of Asia (in German)
- History of Cartography including a discussion of the Geographia
- Dennis Rawlins, Investigations of the Geographical Directory 1979-2007
- Ptolemy's Geography in the Renaissance collected essays