近代大地测量中，是利用恒星来测定地球某两地间子午线弧长的。
Modern geodesy, is used the stars to determine the earth a between meridian arc length.
在测量中已发现纬度越高的地点，子午线每一度的直线距离越短，首次用测量方法证明地球为扁圆形。
The earth was first proved to be an oblate sphere by survey. It was found that the higher the latitude of a place was, the shorter the straight line distance between every degree of meridian was.
只要精确测知一段子午线弧长，便会很容易地计算出地球的周长。
As long as the precise sensing a meridian arc length, we can easily calculate the circumference of the earth.
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