Camera Calibration for Long-Distance Photogrammetry Using Unmanned Aerial Vehicles

The traditional target-dependent camera calibration method has been widely used in close-distance and small field of view scenes. However, in view of the field coordinate measurement in the large-scale monitoring area under the complex field environment, the standard target can hardly meet the requirements of covering most of the camera's field of view. In view of the above problem, a stereo camera calibration method is studied, using the unmanned aerial vehicles (UAV) as feature points, combined with the high-precision position information measured by the real-time kinematic (RTK) positioning system it carries. The measured UAV coordinates are unified in World Geodetic System 1984 (WGS-84). Therefore, through several preset points, the measurement reference coordinate system which is the new world coordinate system we need can be established in any monitoring area, which greatly improves the flexibility of measurement. The experimental results show that the measurement accuracy of the proposed method can reach 0.5% in the monitoring area with a diameter of 100 m. The calibration method has a wide range of application and does not need the traditional standard target, and the measurement reference coordinate system can be established according to the actual needs. It is suitable for field spatial coordinate measurement in long-distance and complex terrain environment.