Research on underground pipeline augmented reality system based on ARToolKit

Augmented Reality (AR) is the overlay of virtual computer graphics images on real world objects, and has many potential applications in industrial operations and academic research. First, this paper discusses the method of camera calibration. ARToolKit provides two calibration approaches: Two Step Calibration Approach and One Step Calibration Approach. Two Step Calibration Approach is more difficult to use, but results in better accuracy (better for 3D measurement). We used ARToolKit's two step method to calibrate our camera. Next, the paper addresses the method of spatial analysis of augmented reality system, data model of spatial analysis, data modeling of 3D pipelines, and the mathematical model of coordinate conversion of 3D pipeline networks. Then, the paper discusses the data structures of underground pipelines. The data structures of underground pipelines include spatial data structure, attribute data structure, and sense data structure. We implemented the display of 3D pipelines in augmented reality, augmented visualization of 3D pipelines based on ARToolKit, information query and spatial buffer analysis of 3D pipelines. Finally, the paper discusses the framework of underground pipeline augmented reality system based on ARToolKit. A hybrid registration based on electronic compass and inclinometer, and a position based on RTK GPS and INS in outdoor AR system are presented. The hardware configuration and software framework of the system and data processing workflow of the combined system are given.