Bleau's map of Asia is framed along the top with city vignette,s of Damascus, Jerusalem, Aden, Hormuz, Goa, Calcutta, Candy, Bantam, and Macao. At the side are the peoples representing the different cultures of the continent.
In his 1569 map, Mercator suggested identifying the Prime Meridian (0° longitude) with a location where the magnetic declination was zero. He believed this passed near the Cape Verde islands or Corvo in the Azores. Blaeu's used Gerard Mercator's projection and based the Meridian on Corvo in the Azores. He used 360 degrees and 10 degree divisions working east. in an anti clock wise direction. It was not know magnetic north moved with time and longitude became speculation. This explained some of the inaccuracy of charts including Bleau's maps However some cartography is speculative, Japan is in the wrong position and curiously falling on its side. While Korea is illustrated as an island and many of the islands in the East Indies are also charted incorrectly.
