测角精度是影响光电经纬仪定位功能的重要因素。为了进一步提高光电经纬仪的测角精度，对测角误差进行详细分析是必要的。从光电经纬仪的总体设计出发，找出了影响测量数据获取、转换、合成中的各项误差源，并详细分析了它们的大小和性质。通过分析光电经纬仪工作原理及结构找出了主要误差源。对机架系统的误差、测角单元误差、电气系统误差、脱靶量误差、大气折射修正误差等主要误差源进行分析计算，并对各单元进行了误差分配。最后，计算了光电经纬仪投影测角精度的均方根值。分析计算结果显示：通过精心设计、加工、检测，修正可使一部分误差减小甚至忽略，但机架系统的误差、测角单元误差、脱靶量误差对测角精度的影响仍很显著；在当前工艺水平下，光电经纬仪事后空间指向精度可以达到σ≤2″。

Angle measurement accuracy plays an important role in photoelectric theodolite positioning and tracking. In order to further improve the accuracy of photoelectric theodiolite, the angle measurement errors were analyzed. Based on the overall design of photoelectric theodolite, the error sources of angle measurement accuracy which effect data acquisition, transformation and synthesis were found, and a detailed analysis of the size and properties was made. This paper first found out the main error sources by analyzing the working principle and structure of photoelectric theodolite. Then, it analyzed and calculated the rack system error, angle measurement system error, electrical system error, off target error, atmospheric refraction correction error, and distributed the error for each system. Finally, this paper calculated the root mean square of photoelectric theodolite′s angle measurement accuracy. The results show that the careful design, machining, testing and correcting could reduce and even ignore errors, but the influence on the angle measurement accuracy of the rack system error, angle measurement system error and off target error is still significant; it is possible to develop the photoelectric theodolite accuracy of spatial point less than 2″ under the current level of technology.