The method of this class is to draw a square grid on the sheet, let each square stand for a set number of li, and draw the land into it to scale.
Pei Xiu of the Western Jin oversaw the Yugong Regional Maps and set out the "six principles of mapmaking"; two of them, scale and orientation, laid the foundation of the square-grid method.
Later maps kept to the method. The Southern Song Map of the Tracks of Yu, cut in stone in the Shaoxing years, mapped the whole realm in squares of one hundred li, and Luo Hongxian's Enlarged Terrestrial Atlas of the Ming drew the whole realm and its frontiers in sheets by the same method.
Grid Cartography is the class in the chapter on Infrastructure on grid mapping: the method of drawing a map to scale on a square grid. Squares are drawn on the sheet, each standing for a fixed number of li, and mountains, rivers and counties can be set into the squares in proportion. Pei Xiu of the Western Jin, the Southern Song Map of the Tracks of Yu and the Ming Enlarged Terrestrial Atlas are three landmarks along the way.
