Accurate Calibration for Large-Scale Tracking-Based Visual Measurement System

Abstract

The combination of a large-field-of-view visual positioning system and a local scanning sensor affords an effective approach to the 3-D measurement of meter-scale objects and has been actively investigated by researchers. The calibration of such an integrated measurement system is essential to establish the overall measurement accuracy. This article proposes to calculate the transformation relationship between the local system and the transfer target through the determination of the scales of the combined system. The principle and implementation of this tracking-based combined measurement system are described in this article, as well as the use of the respective scales of the combined system to establish a model of the applicable geometrical relationships. The Kronecker product was used to solve the model equations, after which homogenous transformation matrix optimization was performed. An error model of the camera-based measurement system was also established based on a combination of the image distortion and the working volume. The 2-D and 3-D errors of the local and global sensors were further quantitatively simulated and visualized to demonstrate the calibration accuracy. Standard plane and complex large object measurement experiments were performed to verify the accuracy of the proposed measurement system and its use for the reconstruction of a large shape.