When Charles Hapgood analyzed the Oronteus Finnaeus and Piri Reis maps with the aid of U. S. Air Force navigators, they deduced that ancient source maps had been used to compile those medieval maps, the ancient source maps having been drawn by a sexagesimal measuring system, like the well known Sumerian base 60, thus suspecting but not knowing that timekeeping was involved (to measure longitude), but now we know how they did it, see Page at right Great Pyramid for Navigation.
