前言我國早在公元前七世紀(春秋、魯文公、宣公時代)之前,已設圭立表來测日影,以最簡單的科學儀器,作最實際的天文研究。可見古代已有人對於理論和實踐的結合,甚為重视了。由陽光投影的結果,可测得太陽年的全長,求出二至(夏至、冬至)和四季的長短。又可以由测影以定南北線(子午線),也可以利 Foreword As early as in the 7th century BC (Spring, Autumn, Lu Wengong, and Xuangong era), China has set up a guillotine to measure the shadow of the sun and use the simplest scientific instruments as the most practical astronomical study. It can be seen that ancient people have attached great importance to the combination of theory and practice. From the results of the solar projection, the total length of the solar year can be measured, and the length of the two (summer solstice, winter solstice) and seasons can be determined. It can also be determined by measuring the north-south line (meridian), but also