Pei Xiu

Pei Xiu (224–3 April 271), courtesy name Jiyan, was a Chinese cartographer, geographer, politician, and writer of the state of Cao Wei during the late Three Kingdoms period and Jin dynasty of China. He was very much trusted by Sima Zhao, and participated in the suppression of Zhuge Dan's rebellion. Following Sima Yan taking the throne of the newly established Jin dynasty, he and Jia Chong had Cao Huan deprived of his position to accord to the will of heaven. In the year 267, Pei Xiu was appointed as the Minister of Works in the Jin government.

Pei Xiu outlined and analysed the advancements of cartography, surveying and mathematics up until his time. he was the first to mention a plotted geometrical grid reference and graduated scale displayed on the surface of maps to gain greater accuracy in the estimated distance between different locations. Historian Howard Nelson asserts that there is ample written evidence that Pei Xiu derived the idea of the grid reference from the map of Zhang Heng (78–139 CE), a polymath inventor and statesman of the Eastern Han period. Robert Temple asserts that Zhang Heng should also be credited as the first to establish the mathematical grid in cartography, as evidenced by his work in maps, the titles of his lost books, and the hint given in the Book of Later Han (i.e. Zhang Heng "cast a network of coordinates about heaven and earth, and reckoned on the basis of it"). Xiu also created a set of large-area maps that were drawn to scale. He produced a set of principles that stressed the importance of consistent scaling, directional measurements, and adjustments in land measurements in the terrain that was being mapped.

The preface to Pei Xiu's written work was preserved in the 35th volume of the Book of Jin, Pei Xiu's maps have since been lost, decayed or destroyed. Yet the oldest existing terrain maps from China date to the fourth century BCE, found in a Qin tomb in present-day Gansu in 1986. Han dynasty maps from the second century BCE were found earlier in the 1973 excavation of Mawangdui. located in the Stele Forest of Xi'an. This three feet squared map features a graduated scale of 100 li for each rectangular grid. China's coastline and river systems are clearly defined and precisely pinpointed on the map. Yu Gong is in reference to the work of the Chinese deity Yu the Great described in the geographical chapter of the Book of Documents, dated fifth century BCE.

Pei Xiu wrote a preface to his maps with essential background information regarding older maps in China. He also provided a great deal of criticism about the existing maps from the Han dynasty in his time. Later Chinese ideas about the quality of maps made during the Han dynasty and before stem from the assessment given by Pei Xiu, which was not a positive one. However, the Qin maps and Mawangdui maps of the Han dynasty discovered by modern archaeologists were far superior in quality than those examined and criticised by Pei Xiu. What these earlier maps did not feature was topographical elevation, which Pei Xiu would outline with his six principles of cartography. Pei 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:

The assumption of power by the great Jin dynasty has unified space in all the six directions. To purify its territory, it began with Yong and Shu (Gansu and Sichuan) and penetrated deeply into their regions, though full of obstacles. Emperor Wen then ordered the appropriate officials to draw up maps of Wu and Shu. After Shu had been conquered and the maps were examined, with regard to the distances from one another of mountains, rivers, and places, the positions of plains and declivities, and the lines of the roads, whether straight or curved, which the six armies had followed; it was found that there was not the slightest error. Now, referring back to antiquity, I have examined according to the Yu Gong the mountains and lakes, the courses of the rivers, the plateaus and plains, the slopes and marshes, the limits of the nine ancient provinces and the sixteen modern ones, taking account of commanderies and fiefs, prefectures and cities, and not forgetting the names of places where the ancient kingdoms concluded treaties or held meetings; and lastly, inserting the roads, paths and navigable waters, I have made this map in eighteen sheets. Pei Xiu states: