Automatic self-calibration of digital cameras for close-range photogrammetry

Digital cameras are getting widely used due to their operation conveniences and real-time processing capabilities. Although digital cameras have been considered suitable to photogrammetric tasks, their metric characteristics are not clear and stable as traditional metric cameras. A real-time on-the-job calibration is, therefore, required before a digital camera can be applied for a photogrammetric task. The technique of self-calibration is considered an effective means for digital camera calibration, but a large amount of image measurements are required. To solve this problem, we designed a new text-coded target and proposed an automatic process to detect, position, and identity the targets. Automatic camera calibration can be achieved by integrating this automatic measuring process and bundle adjustment computation. The experimental results are encouraging and optimally show the feasibility of the proposed method.