Abstract: Collimation method is most commonly used in monitoring of horizontal displacement of a dam. With the popularization and application of total station instead of theodolite, the total station is widely used for horizontal displacement monitoring with the collimation line small angle method. To ensure the accuracy, one or more intermediate stations should be added as the maximum length of the collimation line of concrete dam is more than 300 m, while the maximum length of the collimation line of earth dam is more than 500 m. The analysis and practice of segment monitoring shows that it is of high precision provided that the displacement monitoring precision of the intermediate station is well controlled.

Key words: total station, collimation line small angle method, intermediate station, monitoring precision

摘要： 视准线法是直线型大坝水平位移监测最常用的方法，随着全站仪替代经纬仪的普及应用，采用全站仪用于视准线小角度法监测水平位移也随之普及。为确保小角度法监测精度满足规范要求，对于混凝土坝视准线最大长度超过300 m、土石坝视准线最大长度超过500 m时，可通过在视准线中间增设一处或多处测站的中间设站分段监测法，将原视准线分成两段或多段观测。通过对视准线中间设站分段观测法进行精度分析及实践，得出只要中间设站点本身位移监测精度得到控制，可有效解决过长视准线的水平位移监测精度问题。

关键词: 全站仪, 视准线小角度法, 中间设站, 监测精度