structural:summarization, stylistic:tone, information:extraction, quality:corruption, linguistic:paraphrasing
Cartography

The Wei (220–265) and Jin dynasty (266–420) 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 using a graduated scale, as well as topographical elevation. However, map-making in China had existed since at least the 4th century BC with the Qin state maps found in Gansu in 1986. Pinpointed accuracy of the winding courses of rivers and familiarity with scaled distance had been known since the Qin and Han dynasty, respectively, as evidenced by their existing maps, while the use of a rectangular grid had been known in China since the Han as well. 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. Rafe de Crespigny asserts that it was Zhang who established the rectangular grid system in Chinese cartography. 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. 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 maps (tu) on a same level of importance with documents (shu). It is documented that a physical geography map was first presented by Zhang Heng in 116 AD, called a Dixingtu (地形圖).