全站仪小角法基坑水平位移监测的误差分析与精度控制

Error Analysis and Accuracy Control of the Horizontal Displacement Monitoring of Foundation Pit by Small Angle Method of Total Station

采用视准线小角法监测基坑水平位移,监测点相对于基准线的偏差中误差应满足1 mm^3 mm的精度要求,对观测要求很高。通过分析小角法测量原理和误差来源,讨论了照准误差、测站对中误差和测角误差的影响。在不同偏差中误差控制值和选用不同标称精度全站仪的情况下,应进行理论精度估算并合理确定小角值的测回数。为提高观测精度,提出了工作基点至监测点的距离、小角值测回数和全站仪选型等限制措施,有利于达到预警监控的目标要求。

The small angle method is used to monitor the horizontal displacement of foundation pit,The root mean square error of the monitoring point deviation relative to the datum line should meet the accuracy requirement of 1-3 mm,and the observation requirement is very high.By analyzing the principle and error sources of small angle method,it can be seen that the accuracy of horizontal displacement monitoring is directly related to the horizontal distance from monitoring point to working base point and the error of total station angle measurement. In the case of different control values in root mean square error of deviation and different nominal accuracy of total station,the theoretical accuracy should be estimated and the number of observation set by small angle method should be reasonably determined.In order to improve the observation accuracy and weaken the influence in error of sighting,centring error of the station and error of angle observation,some restrictive measures such as the distance,the number of observation set and the selection of total station are offered,which are useful to achieve the goal of early warning and monitoring.