Thony Christie explores the question of why north is at the top of modern maps by looking in detail at medieval and early modern maps, which had no consensus. “I think that the re-emergence of the Ptolemaic world map at the beginning of the fifteenth century and the development of modern cartography that it triggered which eventually led to the dominance of north orientation in mapmaking, perhaps combined with the increased use of the magnetic compass.”
Over at GeoLounge, Caitlin has a brief and basic overview of medieval maps and travel guides, including T-O maps, travel guides for pilgrims, mappae mundi, and portolan charts. As she points out, only the last of these even attempted to be geographically accurate; the others had other purposes.
— Tim Peake (@astro_timpeake) February 11, 2016