Chinese cartography began in the 5th century BC during the Warring States period when cartographers started to make maps of the Earth's surface. Its scope extended beyond China's borders with the expansion of the Chinese Empire under the Han dynasty. By the 11th century during the Song dynasty highly-accurate maps drawn on grids were produced. During the 15th century, the Ming dynasty admiral Zheng He went on a series of voyages to the South China Sea, Indian Ocean, and beyond and maps for areas outside of China were produced, although world maps covering territories known to the Chinese outside of China existed as early as the Tang dynasty.