1502 World Map of Alberto Cantino
http://upload.wikimedia.org/wikipedia/commons/0/07/CantinoPlanisphere.pngThe Cantino planisphere (or Cantino World Map) is the earliest surviving map showing Portuguese Discoveries in the east and west. It is named after Alberto Cantino, an agent for the Duke of Ferrara, who successfully smuggled it from Portugal to Italy in 1502. The map is particularly notable for portraying a fragmentary record of the Brazilian coast, discovered in 1500 by the Portuguese explorer Pedro Álvares Cabral, and for depicting the African coast of the Atlantic and Indian Oceans with a remarkable accuracy and detail.
In Refuting Gavin Menzies book '1421: The Year China Discovered The World' Turkish Science Professor and historian Fuat Sezgin writes in 'The Pre-Columbian Discovery of the American Continent by Muslim Seafarers':
"On his quest for support of his theories Menzies became aware of the surprisingly modern delineation of Africa, especially of its east coast, on the map charted assumedly in 1502 by Cantino. For Menzies this map “where the coast of East Africa is depicted with such accuracy that it appears to have been drawn with the aid of satellite navigation”
(Note 31) too bears witness to “Chinese expertise”, for “who else but the Chinese could have drawn this astounding chart?” After explaining why the Portuguese can be ruled out as possible originators of the map, he goes on wondering “if Arab navigators could have been the original cartographers.” Menzies’ unconsidered answer is no, because he “found not one detailed Arabic chart of the east coast of Africa in Youssuf Kamal’s Monumenta Cartographica. Although the Arabs understood how to calculate longitude by lunar eclipse, they never mastered how to measure time with the necessary accuracy, something that the Chinese achieved”.
It is impossible to deal at length with all the statements, claims and assumptions Menzies abounds with, yet I would like to concede one point to him,
viz. that
the Portuguese cannot possibly have been the originators of the Cantino map. Not only did they lack proper methods for the determination of longitudes as well as accurate chronometry, but especially because the charting of such a stunningly realistic map of Africa must have been a far more time-consuming project than Menzies seems to realise, a mistake that, incidentally, pervades his whole line of argumentation.
For centuries the Indian Ocean has effectively been like a huge lake enclosed by the Arabic-Islamic culture area. In addition to the familiar methods for the determination of longitudes
on land, the navigators in the Indian Ocean developed a highly sophisticated method of measuring distances on the open sea parallel or oblique to the meridian as well as parallel to the equator. The last case is equivalent to a determination of longitude. It was a true triangulation, suited for reliable and accurate measurements of trans-oceanic distances on the open sea.
Data found in extant Arabic and Turkish navigation manuals from the 9th/15th and 10th/16th centuries confirm that ample and adequate measurements of the Indian Ocean were taken to the extent that a comprehensive cartographic representation was rendered feasible. Hence Wilhelm Tomaschek was able to reconstruct very fine partial maps according to those data available to him in the year 1897, i.e. at a time when the most important Arabic nautical books had not even been rediscovered."
Footnote 31: '1421: The Year China Discovered The World' By Gavin Menzies, page 375f.
Interestingly, this passage has been omitted in the second English edition (page 377).------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'THE PRE-COLUMBIAN DISCOVERY OF THE AMERICAN CONTINENT BY MUSLIM SEAFARERS'
BY FUAT SEZGIN
http://www.laits.utexas.edu/gma/mappamundi/docs/precolumbamerica.pdf