Abstract:Unmanned aerial vehicle photogrammetry without ground control points can effectively improve production efficiency and reduce production costs. This method shows great advantages in areas inaccessible to people. However, there are a number of problems with this method. One of the main problems is that the accurate camera parameters cannot be obtained through the on-the-job calibration method. Inaccurate camera principal distance can seriously affect the object point elevation. The other one is that the projection deformation and earth curvature also have impacts on the elevation accuracy, when the mapping task is carried out in the map projection frame. Therefore, this article analyzes the specific causes of elevation errors and realizes the camera self-calibration in a geocentric frame with control strips. Then, the exterior orientation elements of the images are calculated in the map projection frame without control strips. Finally, the elevation errors caused by map projection deformation and earth curvature are corrected. The experimental results show that the elevation RMSE of the two data sets decreased from 0.298 m and 0.374 m to 0.075 m and 0.080 m, respectively. Elevation accuracy are less than 0.1 m. Therefore, the method in this paper can achieve accurate mapping in a map projection coordinate system without ground control points.