激光雷达技术在应县木塔形变分析中的应用

Application of LiDAR Technology in Deformation Analysis of Yingxian Wooden Pagoda

为了更好地对应县木塔进行保护,需要分析其形变程度,了解木塔的健康状况,进而制定科学的保护方案。利用地面激光雷达、高精度全站仪等测量传感器,通过激光雷达扫描和全站仪控制测量相结合的方案采集监测数据。首先对采集的点云数据进行预处理,外部点云采用整体配准算法进行配准,通过特征进行粗配准和迭代最近点(ICP)算法进行精配准的两次配准,配准后根据控制点完成内、外点云坐标转换,通过罗德里格矩阵求解空间转换参数,最终得到绝对坐标系下的整体点云模型。对点云模型进行多种剖切,测量出柱子的倾斜角度、偏移距离以及整体倾斜角度等数据,定量分析单柱、单层及整体的形变。结果表明:应县木塔各层柱子都存在形变,木塔第2层形变较大,其中M2W23号柱子倾斜最严重;各层均向东北方向有不同程度的倾斜,西南面柱子的位移量普遍较大;从整体上看,木塔向东北方向倾斜并存在着复杂的扭转变形,木塔西侧由南向北发生顺时针扭转,东侧由南向北发生逆时针扭转;应县木塔正处于严重的形变中,急需进行保护。

In order to protect Yingxian wooden pagoda better,it is necessary to analyze the degree of deformation and understand the health status,so as to formulate a scientific protection program.The monitoring data was collected by the combination of lidar scanning and total station control measurement by using ground lidar,high-precision total station and other measuring sensors.Firstly,the collected point clouds data was preprocessed,and the external point clouds were registered by the overall registration method.The internal point clouds performed two registrations of coarse registration through feature and fine registration by the iterative closest point(ICP)algorithm,which were the main data of deformation analysis and required high accuracy.After registration,the coordinate transformation between internal and external point clouds was carried out according to control points.The space transformation parameters were solved by Rodrigues matrix and finally the overall point clouds model in absolute coordinate system was obtained.The point clouds model was cut in various ways to measure the deviation angles and distances of columns and the inclination angles of whole pagoda.Then the deformations of the single column,single layer and the whole pagoda were quantitatively analyzed.The results show that all the columns of Yingxian wooden pagoda are deformed,the second layer of Yingxian wooden tower has a large deformation,of which the M2W23 column has the most serious inclination.Each layer inclines to the northeast in varying degrees,the inclination degree of the southwest columns is generally large.On the whole,the wooden pagoda inclines to the northeast with complex torsional deformation,the west side is turned clockwise from the south to the north,but the east side is turned counterclockwise from the south to the north.In brief,Yingxian wooden pagoda is undergoing serious deformation,which urgently needs protection.