Resection is used to determine the coordinates of an instrument station by performing multiple measurements of points whose coordinate values are known .
后方交会是利用在未知点上对若干已知点进行观测，获得的观测值来计算出未知点的坐标。
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The three coordinate measuring machines, as a kind of measuring instrument, become an indispensable part and are more and more applied to manufacture, electron, automobile and spaceflight, etc.
As a large, multi-functional modern precision instrument, coordinate measuring machine (CMM) has more and more shown its great importance and wide development prospect in industry.