in view of the large-scale and complex field measurement environment, it is difficult and time-consuming to set up field measurement and control points at multiple points. In this paper, the optimization of POS data accuracy by differential method is the research base point, and two-level innovation is carried out based on the post difference principle. Firstly, based on the influence of external orientation elements on the accuracy of POS data, the real POS data is obtained by using camera delay measurement and control technology, and the double difference equation of code pseudo range and carrier phase is fused. The post differential GNSS module based on ubloxn-m8t chip is constructed to eliminate the error of POS data. At the same time, the bundle method area network adjustment model of simultaneous GPS and IMU observation equation is used Through the evaluation of imaging accuracy, it is concluded that the post difference can significantly improve the accuracy of POS data, and the utility is more obvious under few control points and no structure routes.