Because the light of system shines and the distance between the movie camera and granite reference are invariable, the displacement represented by every picture element can be got beforehand by the means of experiment mark method.

• 由于系统的光照条件及摄影机到花岗岩基准平台表面的距离都是固定的，所以通过实验标定的方法可以预先求得每个像素所代表的位移量。