Pei Xiu
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: