pyramidal error of prism

The submerged tube section can not be observed directly,whereas its location could be known by means of the prism tower.

沉管在海底的位置靠露在水上的测量棱镜塔目标位置反求,为及时知道水下对接数据,调整施工,要求计算机实时通讯,同步观测棱镜目标,实时显示水底管段的位置特征。