全站仪自由设站三维量测中的计算误差分析

Calculation Error Analysis in Three-dimensional Measurement Based on Free-stationing of a Total Station

针对隧道施工中采用全站仪自由设站进行三维量测时存在数据前期上下波动,长期变形趋势又比较明显等问题,文章对三维测量中的计算误差进行理论推导分析。研究结果表明,将整体坐标转化为局部坐标时会带来计算误差,测点C到基准点A的距离L_(ac)与两基准点A、B之间的距离L_(ab)的比值对仪器误差具有放大效应。鉴于此,文章提出两基点A、B同侧的测量方法,可以很好地减小计算中带来的误差。

The issues such as early-fluctuating of data and obvious trend of long-term deformation are faced when three-dimensional measurement in tunnel is taken based on free-stationing of a total station.So the calculation errors in three-dimensional measurement are theoretically deduced and analyzed.The studies show that:while transforming of global coordinate into local coordinate it would cause the calculation errors,and the specific value of Lac(the distance from measuring point C to benchmark point A)to Lab(the distance between benchmark points A and B)has an amplifying effects on instrumental errors.The measuring method on the same side of benchmark points A and B is hence proposed and the engineering cases prove that the calculation errors could be perfectly reduced by such method.