| Over time,whether it is ancient buildings or modern high-rise buildings,there are more or less deformations that are influenced by the basic and structures of the building,and the external environmental impacts,which specifically manifested as the tilt deformation of the entire building.Tilt monitoring is an important part in the field of deformation monitoring,which is especially important for urban security development at this stage.In recent years,threedimensional laser scanning technology breaks through its high-precision,non-contact measurement,real-time dynamic three-dimensional,efficient and high characteristic advantages,and provides new technical means for architectural tilt monitoring.With the rapid development of the construction industry,the architectural style has gradually developed from the traditional regular symmetrical buildings to the regular asymmetrical buildings and irregular buildings without a central axis.How to use 3D laser scanning technology to monitor the tilt of special buildings has become a research hotspot.In view of this,this paper is based on Xi’an Big Wild Goose Tower’s measured point cloud data and modern high-rise building model data,this paper studies the change law of the coordinates of the point cloud of the building under the inclined state.The experimental verification and application are studied,and a method for monitoring the inclination of buildings with a central axis and buildings without a central axis is proposed and verified—the Z coordinate inclination monitoring method of contour points.The main research contents and results of this thesis are as follows:(1)Systematically expounds the characteristics,principles,error sources,application and data processing of 3D laser scanning technology in tilt monitoring.Aiming at the source of errors in the data acquisition of 3D laser scanning technology,a data acquisition scheme is designed.According to the influence of the distance and the incident angle of the station on the data acquisition,based on the geometric relationship,the instrument station scheme is optimized to reduce the transmission of data errors.(2)Through point cloud data processing,ground point cloud data purification,point cloud data compression and simplification,large-scale and small-scale point filtering,building edge smoothing,building contour feature point extraction are realized;An algorithm of contour points extraction based on z-coordinate of contour points was designed,and the authenticity of extracted contour points was compared and verified together with the longitude and latitude scanning method.Finally,the filtering and denoising of the measured point cloud data of Xi’an wild goose pagoda and the extraction of contour points are completed.(3)This paper analyzes the advantages and disadvantages of the commonly used building inclination monitoring method "fitting central axis method",explores the change law of Z coordinate under the condition of building inclination,and puts forward a new inclination calculation method based on building point cloud data-"z-coordinate method of contour point".The feasibility of "z-coordinate method of contour point" is verified by the comparison experiment of Xi’an wild goose pagoda inclination calculation and the simulation experiment of modern building inclination.(4)The "contour point Z coordinate method" is used to monitor the inclination of buildings without central axis.The experimental results show that,compared with the fitting center axis method",the "contour point Z coordinate method" can not only calculate the inclination change of a building without a center axis in two phases,but also calculate the real inclination of the building in each phase,which provides a new data processing scheme for the inclination monitoring of this kind of building. |
