3D Change Detection Method for Exterior Wall of LNG Storage Tank Supported by Multi-Source Spatial Data

Change detection methods for measuring deformation of the LNG storage tank's exterior wall cannot meet the requirements for extensive and comprehensive deformation analysis. The method proposed in this paper uses multi-source spatial data to detect the deformation of the LNG storage tank's exterior wall. Exterior wall data collected simultaneously by terrestrial and airborne laser scanners, as well as close-range and oblique photogrammetry, are pre-processed separately and then registered to the global point clouds. The deformation state of exterior wall is represented by a thorough assessment approach that takes into account four change indices. The results suggest that the registration precision of global point clouds is 6 mm. The global ovality of the LNG storage tank is 0.053%, with a tilt change of 2.58 degrees and a deviation of 27 mm in the direction of the azimuth of 321.98 degrees, an average value of 0.07 mm for depression and protrusion deformation, and a surface flatness of 21.3 mm. In this case, the flatness is greater than the variation threshold of the standard specification, indicating that the tank may have structural uneven settlement or other deformation problems. The attraction of the proposed method resides in its capacity to efficiently and accurately obtain spatial positioning and color information of the LNG storage tank's exterior wall, thereby providing a robust foundation for precise judgments regarding the deformation state. In this study, spatial localization and visual data are integrated for the full data acquisition of the LNG storage tank's exterior wall, and a step-by-step registration method is used to produce the global point clouds. 3D deformations of the exterior wall are systematically described in different dimensions, from global to local.image