Pei Xiu
In the year 267, Pei Xiu (224–271) was appointed as the Minister of Works by Emperor Wu of Jin, the first emperor of the Jin Dynasty. Pei is best known for his work in cartography. Although map making and use of the grid existed in China before him, he was the first to mention a plotted geometrical grid and graduated scale displayed on the surface of maps to gain greater accuracy in the estimated distance between different locations. Pei outlined six principles that should be observed when creating maps, two of which included the rectangular grid and the graduated scale for measuring distance. Western historians compare him to the Greek Ptolemy for his contributions in cartography. However, Howard Nelson states that, although the accounts of earlier cartographic works by the inventor and official Zhang Heng (78–139) 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.