see many interesting links in http://de.wikipedia.org/wiki/Gerhard_Mercator
Mokre 2005: 18 & 61 ; ADB 21 (1885): 385-97 ; Nicholas Crane: G. M.: The man who mapped the planet (London 2003) ; Rienk Vermij (ed.): G. M. und seine Welt (1997) ; J. Blake: Vermessung der Welt (2007: 17f.) ; Grees 2002: 21f. ;
Active as cartographer, cosmographer, since 1552, active in Duisburg, a major citiy in the Duchy of Cleves, where he opened a cartographic workshop, also active as surveyor & mathematics teacher at the academic college of Duisburg.