Editing Zhang Heng (section)

===Cartography===
[[File:Western Han Mawangdui Silk Map.JPG|thumb|An early Western-Han (202 BC – AD 9) [[Mawangdui silk texts|silk]] [[History of cartography|map]] found in tomb 3 of [[Mawangdui]], depicting the Kingdom of [[Changsha Kingdom|Changsha]] and Kingdom of [[Nanyue]] in southern China (note: the south direction is oriented at the top, north at the bottom)]]

The [[Cao Wei|Wei]] (220–265) and [[Jin dynasty (266–420)]] [[History of cartography#China|cartographer]] and official [[Pei Xiu]] (224–271) was the first in China to describe in full the geometric [[grid reference]] for maps that allowed for precise measurements [[Scale (map)|using a graduated scale]], as well as topographical [[elevation]].<ref>Needham (1986), Volume 3, 538–540.</ref><ref name="hsu 1993 97">Hsu (1993), 97.</ref> However, map-making in China had existed since at least the 4th&nbsp;century&nbsp;BC with the [[Qin (state)|Qin state]] maps found in [[Gansu]] in 1986.<ref>Hsu (1993), 90.</ref> Pinpointed accuracy of the winding courses of rivers and familiarity with scaled distance had been known since the [[Qin dynasty|Qin]] and Han dynasty, respectively, as evidenced by their existing maps, while the use of a rectangular [[Grid graph|grid]] had been known in China since the Han as well.<ref name="needham 1986 volume 3 106 107">Needham (1986), Volume 3, 106–107.</ref><ref name="hsu 1993 90 97">Hsu (1993), 90 & 97.</ref> Historian Howard Nelson states that, although the accounts of Zhang Heng's work in cartography are somewhat vague and sketchy, there is ample written evidence that Pei Xiu derived the use of the rectangular grid reference from the maps of Zhang Heng.<ref name="nelson 1974 359">Nelson (1974), 359.</ref> Rafe de Crespigny asserts that it was Zhang who established the rectangular grid system in Chinese cartography.<ref name="crespigny 2007 1050"/> Needham points out that the title of his book ''Flying Bird Calendar'' may have been a mistake, and that the book is more accurately entitled ''Bird's Eye Map''.<ref>Needham (1986), Volume 3, 538. "the title may have referred to a Bird's Eye Map&nbsp;... that Chang Heng occupied himself with map-making is sure&nbsp;... a physical geograph map was presented by him".</ref> Historian Florian C. Reiter notes that Zhang's narrative "Guitian fu" contains a phrase about applauding the maps and documents of [[Confucius]] of the Zhou dynasty, which Reiter suggests places [[Gazetteer#China|maps (''tu'')]] on a same level of importance with [[Four Books and Five Classics|documents (''shu'')]].<ref>Reiter (1990), 320.</ref> It is documented that a physical geography map was first presented by Zhang Heng in 116 AD, called a ''Dixingtu'' (地形圖).<ref>Needham (1986), Volume 3, 538.</ref>