ABSTRACT
As an accomplished cartographer, Columbus constructed and carried with him on the voyage several maps, depicting expected zones of contact, island or mainland regions. These maps, now lost to history, were built on knowledge obtained from prior portolan charts and mappae mundi drawn by Portuguese, Spanish, and Italian cartographers, including the 1482 Ptolemy map. Using these map sources and written accounts, Columbus estimated the distance across the Ocean Sea. He understood that there would be several distinct steps, or sequences, to the crossing, including stopping at the Canary Islands, striking out into the known part of the Ocean Sea, entering and moving through a vast unknown portion of the ocean, and finally encountering islands of the Indies, and hopefully, the Asian mainland.
