Maps In early China maps were used as symbols of regional power and as certificates of sovereignty. From the Eastern Han (25-220 C.E.) into the Qing dynasty, policy required every state of the empire to periodically submit a map to the imperial court as a means of ensuring central control. After the late sixteenth century, a succession of Western missionaries brought to China many printed books about Western scientific methods, including cartography. The introduction of Mercator maps, scales of longitude and latitude, triangulation, and other cartographic methodologies changed the course of mapmaking in China. The National Library of China's collection of maps numbers some 30,000 and spans the history of mapmaking in China.