A joint measurement method integrating stereo-vision-tracked laser scanning and laser-tracker referencing: depth-stratified calibration-position design

Large-scale inspection requires both dense surface data and a stable global reference, which are difficult to obtain with a single instrument. This paper proposes a joint measurement method integrating a laser scanner, a stereo-vision tracking unit, and a laser tracker. In the proposed method, the scanner captures dense local surface data, the stereo-vision unit determines the scanner pose, and the laser tracker establishes the global reference by observing a scanner-mounted spherically mounted retroreflector (SMR). Paired observations of the same SMR center connect the tracking and laser-tracker frames, forming a unified coordinate chain that transforms local point clouds into the global frame. To ensure the accuracy of this joint measurement chain, a depth-stratified calibration-position design is further introduced to account for distance-dependent stereo uncertainty. The 3–6 m working volume is divided into near, middle, and far ranges, and eleven 12-position layouts are assessed by Monte Carlo simulation and repeated experiments. The results show that middle-dominated mixed-depth layouts consistently achieve low error levels, with the 3/6/3 (S7) and 2/8/2 (S8) near/middle/far configurations showing particularly favorable performance. For S7, the mean SMR-center consistency residuals are 0.101 mm and 0.106 mm for the fixed and estimated SMR-center modes, respectively, corresponding to reductions of 13.1% and 11.5% relative to the near-only layout. These results support distance-aware calibration-position planning for the 3–6 m, 12-position configuration investigated in this study and the proposed cross-system coordinate framework.