A total pointing error correction model was built to correct the pointing errors of a level mounting theodolite. Based on the opto-mechanical structure of the level mounting theodolite, a geodetic coordinate system and a pointing coordinate system were built. Then,according to the location relationship between the two coordinate systems, the target coordinate in the geodetic coordinate system was expressed. After a total differential for the target coordinate, an equation was obtained to describe the relation between target coordinate error and longitude & latitude errors of the level mounting theodolite. By considering the three shafting errors to be the major ones of the system, 5 linear coordinate transformations were performed to deduce a total coordinate error equation for three shafting errors. Combined with the total differential equation,a unitive compensation model of pointing error on the three shafting errors was obtained. By linear superposition with the pointing error caused by ehcoder errors, the total pointing error of the level mounting theodolite was gained. Finally, 46 stars scattered in sky space uniformly were selected to be measured, and the discrete values of the 46 stars’ pointing errors were gained in longitude and latitude dimensions, respectively. After least square fitting, the undetermined coefficients in the total pointing error model were obtained. Experimental results indicate that the total pointing accuracy can rise from 40. 1" to 3.4＂ after correction, which meets the accuracy request in a general design.%为修正水平式经纬仪的指向误差,提出了一种针对视轴指向的统一补偿模型.根据水平式经纬仪的光机结构,建立了照准坐标系和地平坐标系;通过两坐标系的几何关系得到目标在地平坐标系下的坐标方程,并对该方程进行全微分,得到地平坐标误差与指向误差的关系式.针对设备主要误差源之一(3轴误差)进行5次线性变换,推导出目标在地平坐标系中关于3轴误差的统一地平坐标误差方程;结合全微分所得关系式,求出指向误差关于3轴误差的统一补偿模型,将该模型与编码器误差模型线性叠加后获得水平式经纬仪指向误差的统一补偿模型.最后,对全天分布较为均匀的46颗恒星进行观测,得到了观测误差的实验数据,利用最小二乘法对该模型进行拟合,得到模型中各待定系数.实验结果表明,采用该模型进行修正后,设备总指向精度由修正前的40.1"提高到3.4",满足系统总体提出的精度要求.
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