Stepwise calibration method for the overview camera of an image-assisted total station

Combining total station and camera, the system measures large dynamic objects. Current calibration mainly covers coaxial and external cameras, lacking research on the vital built-in overview camera of image-assisted total stations. This paper builds its image measurement model and develops overall and stepwise calibration methods. The overall method is unstable and range-limited, whereas stepwise calibration achieves effective parameter decoupling. On this basis, fourth-order bivariate Fourier APs are used for distortion compensation. After correction, MAE and Std reach 0.07 and 0.09 pixels in both x and y directions, offering reliable references for practical calibration.