摘要
针对砖混建筑物,通过三维激光扫描技术进行数据观测,以墙体长度为监测指标,进行变形监测.首先,基于墙体点云厚度,在确定距离阈值后,经建筑点云分割、墙体点云再分配实现建筑物墙体拆分.其次,以单面墙体为基本单位,进行墙体边界点估计,该估计方法由基于法线的点云边界估计方法变化得到,仅需计算一次线,转换一次坐标系.然后,基于上边界点,将选权迭代最小二乘法引入,同时在相邻两上边界线相交于一点的约束下,进行该线拟合.再次,由上边界线,在墙体上创建可向下平移的兴趣区域,每次平移后,结合区域内垂直边界点所在直线,计算墙体长度.最后,对于两次连续观测,将相同平移次数获取的墙体长度做差,以实现变形值提取.结果表明,由该方法计算的墙体长度而获取的变形情况,与墙体裂缝表现的变形情况基本吻合.且墙体长度的计算误差分布在-3～7 mm,可以达到毫米级精度.
Abstract
This study applies terrestrial laser scanning technology for data measurement in brick-concrete structures,using wall length as the primary index to monitor deformation.Firstly,after determining the two distance thresholds based on thickness,the single wall point cloud is acquired by building point cloud segmentation and wall point cloud redistribution.Secondly,using the single wall as the fundamental unit,the wall boundary points are estimated.This estimation method is changed from the point cloud boundary estimation method based on normal.It only needs to calculate the normal once and convert the coordinate system once.Thirdly,with the con-straint that two adjacent top boundary lines intersect at a point,the top boundary line is fitted by the weighted iterative least squares method.Fourthly,for single wall,a downward-translatable interest region is created and the structural length in the region is calculat-ed.Finally,for two consecutive measurements,the wall lengths obtained of the same translations times are difference to extract the de-formation values.The results show that the deformation discerned from the wall length calculated through this method aligns with the deformation represented by wall fractures.Furthermore,the computational error associated with the wall length ranges between-3 mm and 7 mm,thereby attaining millimeter level precision.
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