Xiu also referred to Xiao He (died 193), who assembled the maps made during the fall of the Qin dynasty. This was done after the founder of the Han dynasty, Liu Bang (died 195 BC), had sacked the city of Xianyang. Pei Xiu states: Pei Xiu continues his preface with short background information on the conquests by the Jin dynasty and the impressive maps commissioned by Sima Zhao (211–264). He then described the methods he used to create new maps while examining the ancient text of the Yu Gong or Tribute of Yu to create historical maps: Pei Xiu outlined six principles that should be observed when creating a map. He then defended his position and each of the six principles with a short explanation as to how they provide better accuracy in map-making and cartography. The first three principles outlined the use of scale (fenlü), direction (zhunwang) and road distance (daoli), while the last three principles are used to properly calculate distances on uneven terrain as represented on a flat, two dimensional map. Pei Xiu states: See also Lists of people of the Three Kingdoms Notes References 224 births 271 deaths 3rd-century geographers Cao Wei politicians Chinese cartographers Chinese geographers Chinese non-fiction writers Jin dynasty (266–420) politicians Jin dynasty (266–420) writers Pei clan of Hedong Scientists from Shanxi Writers from Shanxi