Areas of the World surveyed
The enormity of the task at hand would have required huge fleets for its completion.
Indian Ocean (Cantino and Zheng He’s passage charts)
Nine million square miles and thousands of islands. Assuming ships 15 miles apart, they sail at 4.8 knots and survey for 10 hours a day, then 30 ships would have had to be at sea for 18 months.
South America and Antarctic (Piri Reis and Zheng He’s passage charts)
Approximately 6 million square miles – about 20 ships required over an 18-month period.
North America and North Atlantic (Cantino)
Approximately 12 million square miles – about 40 ships.
Far East (Rotz)
Not fewer than 20 ships over an 18-month period.
Australasia (Rotz and Zheng He’s passage charts)
No fewer than 20 ships over an 18-month period.
Rivers of the World (Waldseemueller)
Thousands of miles of the Orinoco, Amazon, Mississippi; hundreds of miles of rivers in Siberia and Australia and rivers in Pacific America are depicted on European charts before voyages of discovery.
No fewer than 130 ships over 18 months would be required. The only nation who could put such a huge fleet to sea to provide the original information later shown by cartographers of the Piri Reis, Cantino, Jean Rotz, Waldseemueller, Pizzigano and Zheng He’s passage charts (all showing lands drawn before Europeans “discovered” them) was China.