Error analysis of star image coordinate based on digital zenith camera

The accuracy of the star image coordinates is closely related to the positioning accuracy of the digital zenith camera. On the basis of the principle of digital zenith camera imaging, the star image coordinate expression was deduced strictly. The error equations of the image coordinates under four error factors and composite error factor were deduced based on the star image coordinate expression. The analysis results showed that the errors were independent of each other. Star map data was obtained through the simulation under four error factors and composite error factor. The simulation results show that:The influence of the image coordinates of each star point caused by the focal distance error and the transposition error is different. Compared to average value of the coordinate change values of x and y, the maximum fluctuation values of x and y caused by the focal distance error were about 2.38 pixel and 3.04 pixel. The maximum fluctuation values of x and y caused by the transposition error were about 1.06 pixel and 1.41 pixel. The error of the optical axis tilt and the main point offset made the change of the star image coordinates as whole migration. In addition, a method for solving the error parameters was proposed. The calculated error parameters were used to compensate the star image coordinates. The longitude accuracy of the digital zenith camera was improved by about 1.98 m, and the latitude accuracy was improved by about 1.65 m.