We know that astronomers and architects in the ancient and medieval world were capable of formidable feats of measurement and geometric design. The existence of the Antikythera mechanism despite no known contemporary written accounts of such mechanisms or their uses shown just how many very large holes there are in our understanding on the state of the art in ancient world science and technology in this area. Even Eratosthenes map of the Mefiteranean and Black Sea from circa 194 BC are easily recognisable and contain all the main geographic features and rough proportions. Even the map of Britain is a half decent approximation for someone in Alexandria.<p>Navigators must have had access to all the same instruments and mathematical knowledge, and had a very considerable interest in using them effectively. The results would also have been a vital competitive advantage. As the linked article says, these charts were considered state secrets.<p>But obviously, it must have been alien Atlantans from Mars. Or something.
I think that people constantly devalue the achievements and accomplishments of the ancients (in this case, not ancients literally, but medieval people), and feel like they need to resort to lost civilizations or geniuses in the Elysian past.
Especially with the Middle Ages-no one wants to admit that they were capable of engineering or scientific achievements.
Unfortunately, the dissertation under discussion here isn’t actually available for reading. <a href="http://dspace.library.uu.nl/handle/1874/291367" rel="nofollow">http://dspace.library.uu.nl/handle/1874/291367</a>
“Full Text: Embargo until March 01 2018”<p>There’s been a lot of theorizing about the Portolan charts (cf. this bibliography <a href="http://www.maphistory.info/portolanref.html" rel="nofollow">http://www.maphistory.info/portolanref.html</a>). Claims that they use a Mercator projection per se seem dubious to me.<p>See this set of presentation slides by Waldo Tobler for a fun view, which the recent analysis in the linked article purports to debunk, <a href="http://www.geog.ucsb.edu/~tobler/presentations/Portolani.pdf" rel="nofollow">http://www.geog.ucsb.edu/~tobler/presentations/Portolani.pdf</a>
tl;dr maps From 13th Century Europe are scarily accurate, use Mercator style projection and have no obvious antecedents<p>The level of sophistication of science in medieval Europe may be way ahead of what we assume (have we even tried to measure it?).<p>Cartography may well have been leap frogged by one forgotten expedition but things like the Antekythera mechanism keep pointing to unsung genius and strong civilisation that we just assume did not exist - what if we were judged not by Feynmann but by Trump in 1000 years time?
The Mercator <i>style</i> projection is interesting.<p>My rank speculation is that the originals were drawn during the Roman empire on spheres and then taken off to form the mosaic.
Fixed link to Uni Utrecht press release:
<a href="http://www.uu.nl/en/news/origin-of-medieval-sea-charts-disproven" rel="nofollow">http://www.uu.nl/en/news/origin-of-medieval-sea-charts-dispr...</a><p>Open access version of one of the student's recent articles:
<a href="http://dspace.library.uu.nl/bitstream/handle/1874/327279/Nicolai.pdf?sequence=1" rel="nofollow">http://dspace.library.uu.nl/bitstream/handle/1874/327279/Nic...</a><p>The thesis is not public as he's written a book on this: <a href="http://www.brill.com/products/book/enigma-origin-portolan-charts?page=4" rel="nofollow">http://www.brill.com/products/book/enigma-origin-portolan-ch...</a>