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Investigation on image precision for camera parameters using target and target-free calibration

The accuracy of the image is dependent on the quality parameters of camera. The camera parameters is obtained from the target calibration of the test bench in past. Recently, the image processing software can be dealt with the target-free calibration by internal programming. In this research, the images of unmanned aerial vehicle (UAV) are examined by two types of processes, target calibration and target-free calibration to investigate the precision difference of ortho-photo for these. First, the target and target-free calibration of the Canon 600D is setup in the indoor scene. Second, the pictures of dome and playground of Chia Nan University at height 300m are taken using the 6-axis UAV. The results show that the image precision of target calibration is better target-free calibration, since it is dependent with the number of ground control points in aerial photometry. However, the image precisions of two calibration approach are coincidence when the number of ground control point is increased. In future, the good camera precision can be derived with suitable number and location of ground control point without pre-target calibration.