Piri Reis map - who or what charted land masses before they were believed to have been discovered?

There’s an ancient map, called the Piri Reis Map, that has scientists scratching their heads and ttheologians saying, “We told you so”. It is extremely accurate and charts much of the land that had yet to be discovered at the time of its creation. Even more remarkably, it charts the Antarctica land mass which was not even possible until ground penetrating radar was invented (in the 1800’s) that would allow map makers the ability to peer beneath the mile-thick ice covering.

Piri Reis map - who or what charted land masses before they were believed to have been discovered?