Keywords: Anonymous Portuguese map c.1471 (Estense).jpg en Portolan chart by anonymous Portuguese cartographer held CGA5C by Biblioteca Estense Modena This is the oldest Portuguese nautical chart in existence Estimated date c 1471 shortly after the voyage of Pêro Escobar and João de Santarém c 1470 to the Gulf of Guinea and definitely before 1482 Biblioteca Estense Modena Unknown Portuguese cartographer ~ 1471 PD-old Portolan charts made in the 15th century 1471 Modena Biblioteca Estense manuscripts |