In ancient China, gnomon shadow measurement, as a basic technique for astronomy, was important not only astronomically, but also culturally. Compared to sunrise observation for the determining the seasons of the year, gnomon shadow measurement was valid for a much larger area. Therefore it indicates the transition of civilization from ＂local＂ to ＂universal＂. Archaeoastronomical studies show that both gnomon shadow measurement and sunrise observation were invented during the Taosi Culture period （2300-1900 B. C. ） , which means a certain form of ＂imperial culture＂ had come into existence. Gnomon shadow measurement became a technique for ＂empire-building＂. The rulers applied this technique to the determination of orientations and setting the boundaries of the country. The ＂center of the land＂, which symbolized the ＂center of power＂, was also determined by the gnomon. Changes in the shadow length indicated changes in the location. The Chinese established the law of ＂qian li ca yi curt＂, which means the shadow length would increase or decrease one cun for every thousand li the gnomon was moved to the north or to the south of the ＂center of the land＂. Based on this principle, the Chinese developed a feudal ritual that different sizes of the jade gnomons held by those who had been enfeoffed symbolized the different sizes of their fiefdoms. Since the 1 s, century B. C. , gnomon shadow measurement has played an important role in state-controlled calendar making activities.