Research on 3D Reconstruction Procedure of Marked Points for Large Workpiece Measurement

Digital close-range photogrammetry has been used increasedly in various engineering projects. By using digital cameras along with image processing, camera calibration and bundle adjustment method, measurements with high precision can be achieved. Based on analyzing the characteristics of 3D measurement for large workpiece and its actual demand, a procedure of reconstructing marked points is proposed in this paper. In the procedure, the initial value of camera parameters and 3D coordinates of marked points is computed by optimizing alternately and spreading from the selected images to the other. The 3D coordinates of all marked points are obtained by using bundle adjustment method, in which camera parameters and 3D coordinates of all marked points are optimized at the same time. Camera calibration is the key to get high-precision 3D information from a sequence of 2D images in close-range photogrammetry. In this procedure, iterative optimization strategy is used for camera calibration, which can improve the accuracy of 3D coordinates gradually. The procedure is effective and flexible. The experimental results proved that this method can meet the needs of 3D measurements and other practical engineering applications.