Application of Three-dimensional Laser Scanning Technology in the Teaching Practice of Surveying and Mapping of Ancient Buildings

Based on the study of the application of three-dimensional laser scanning technology in ancient building surveying and mapping,this paper briefly describes the working principle and flow of three-dimensional laser scanning technology.Based on the practical application,this paper puts forward the discussion of related problems and matters needing attention.This has a certain reference significance for the study of new technology in surveying and mapping of ancient buildings.

Slope excavation quality assessment and excavated volume calculation in hydraulic projects based on laser scanning technology

Slope excavation is one of the most crucial steps in the construction of a hydraulic project. Excavation project quality assessment and excavated volume calculation are critical in construction management. The positioning of excavation projects using traditional instruments is inefficient and may cause error. To improve the efficiency and precision of calculation and assessment, three-dimensional laser scanning technology was used for slope excavation quality assessment. An efficient data acquisition, processing, and management workflow was presented in this study. Based on the quality control indices, including the average gradient, slope toe elevation, and overbreak and underbreak,cross-sectional quality assessment and holistic quality assessment methods were proposed to assess the slope excavation quality with laserscanned data. An algorithm was also presented to calculate the excavated volume with laser-scanned data. A field application and a laboratory experiment were carried out to verify the feasibility of these methods for excavation quality assessment and excavated volume calculation. The results show that the quality assessment indices can be obtained rapidly and accurately with design parameters and scanned data, and the results of holistic quality assessment are consistent with those of cross-sectional quality assessment. In addition, the time consumption in excavation quality assessment with the laser scanning technology can be reduced by 70%e90%, as compared with the traditional method. The excavated volume calculated with the scanned data only slightly differs from measured data, demonstrating the applicability of the excavated volume calculation method presented in this study.

Study on Estimation Method of Rock Mass Discontinuity Shear Strength Based on Three-Dimensional Laser Scanning and Image Technique

The estimation of shear strength of rock mass discontinuity is always a focal, but difficult, problem in the field of geotechnical engineering. Considering the disadvantages and limitation of exist- ing estimation methods, a new approach based on the shadow area percentage （SAP） that can be used to quantify surface roughness is proposed in this article. Firstly, by the help of laser scanning technique, the three-dimensional model of the surface of rock discontinuity was established. Secondly, a light source was simulated, and there would be some shadows produced on the model surface. Thirdly, to obtain the value of SAP of each specimen, the shadow detection technique was introduced for use. Fourthly, compared with the result from direct shear testing and based on statistics, an empirical for- mula was found among SAP, normal stress, and shear strength. Data of Yujian （~ River were used as an example, and the following conclusions have been made. （1） In the case of equal normal stress, the peak shear stress is positively proportional to the SAP. （2） The formula for estimating was derived, and the predictions of peak-shear strength made with this equation well agreed with the experimental re- suits obtained in laboratory tests.

三维激光扫描技术在古建筑木结构测绘中的运用

为了确保历史建筑的完整性和稳定性,对其进行保护维修都需要准确的测绘数据。利用三维激光扫描技术,取代传统的单点立面测绘技术对历史建筑进行保护。该方法能最大程度地节省人力成本,提高工作效率。探索三维激光扫描技术在古代建筑勘察中的运用,阐述其基本原理和优点。通过在实际案例中的应用,三维激光扫描技术在古建筑的外观检查上展现出巨大的潜力,为保护和传承历史文化建筑遗产提供了有力保障。

Experimental and Numerical Investigation on the Ultimate Strength of Stiffened Plates with Scanned Initial Geometrical Imperfection

The study of the ultimate strength of stiffened plates is a hot topic in ocean engineering. The ultimate strength and behavior of collapse of stiffened plates were investigated using experimental and numerical methods. Two stiffened plates, with one and two half-bays in both longitudinal and transverse directions, were tested under the uniaxial compression. There were clamped boundaries at both ends of the stiffened panels and a restrained boundary on the transverse frames. The novel three-dimensional laser scanning technology was used to measure the initial geometric imperfections and the ultimate deformation of the stiffened panels after the test. The initial geometric deformation was imported into the finite element model, and the ultimate strength and behavior of collapse of the stiffened plates were calculated using the finite element analysis. FE analysis results based on the measured initial geometric imperfections were compared with the test results. It is concluded that structural deformation can be well measured by three-dimensional laser scanning technology, and can be conveniently imported into the finite element analysis. With the measured initial geometric imperfections considered, the FE analysis results agree well with the experimental results in ultimate strength, behavior of collapse, and the ultimate displacement distribution of the stiffened panels.

基于3D激光感知的隧道爆破参数优化设计方法

为解决隧道爆破质量控制困难的问题,探究新型爆破参数优化方法,提出一种3D激光扫描技术与BP神经网络相结合的实时优化方法,对隧道爆破超欠挖感知及其后续钻爆参数进行实时修正,构建现场扫描方法、数据处理、点云提取与超欠挖图像等工作程序,建立BP神经网络模型、算法并确定模型参数。通过试验验证表明:1)将3D激光扫描技术应用于隧道爆破超欠挖质量感知中切实可行,与人工测量结果吻合较好,具有快速、实时和准确的优点;2)采用3D激光扫描方法能够对隧道爆破后的断面轮廓线进行精确评测,在获取爆破超欠挖的精细数据后,通过样本学习完成模型训练能推理出较为合理的爆破参数,改进后的优化方案使平均超挖降低54.8%。

移动式三维激光扫描在轨道交通结构变形监测中的应用

针对轨道交通作业窗口“受限”且传统测量手段无法全面获取隧道状态的问题,本文借助移动式三维激光扫描系统,结合实际工程案例对轨道交通结构进行检测,首先推导了三维激光扫描的基本原理和坐标转换数学模型,通过外业数据采集、内业数据处理获取了隧道点云数据。对比分析临近地铁隧道的深基坑项目施工前后三维激光扫描数据,结果表明:基坑施工过程对隧道结构产生了一定影响,且基坑正对影响区域结构变形最大,外扩影响较小,净空收敛累计变化量最大,为15.4mm。同时使用全站仪对三维激光扫描获取的净空收敛结果进行精度评估,结果证实了:移动式三维激光扫描测量隧道净空收敛和全站仪测量净空收敛累计变化量总体一致性较好,其中83.33%的监测断面累计变化量互差小于2mm。

基于点云的多源数据融合技术

三维激光扫描技术是一门逆向工程应用技术,凭借其高速、全面且高自动化的特点,显示出了强大的不可替代性。三维点云数据有着其多样化、精度高、数据完整的优点。多源数据融合技术使不同设备获取的点云数据、影像数据、空载数据能够相互弥补,提高不同场景环境下的作业效率,完善数据的结构和精度质量,使空、地、水下三维数据的一体化成为可能。通过对不同射程多台三维激光扫描仪的数据进行相对精度分析、调整和融合,并对不同融合方法获取的多源融合数据进行精度验证,探索一种多源数据融合的方法,形成多源数据融合的通用技术流程。为多种载体三维激光扫描技术的数据和影像数据的融合方法研究奠定基础。

移动式三维激光扫描系统在地铁隧道病害检测中的应用

在地铁运营过程中,地铁隧道及其附属构建筑物会出现结构渗水、掉块和环片错台等病害情况,传统检测方法存在难以精确量化、检测效率低、容易漏检等缺点。为了解决这些问题,将移动三维激光扫描系统应用于地铁运营病害检测中,首先采集隧道空间的三维点云信息,再对轨道移动小车、架站式、手持式等不同移动三维激光扫描系统内外业效率、精度情况进行对比分析,总结移动式三维激光扫描系统内外业的生产流程,结合地铁工点采集的隧道三维点云数据,探讨不同三维激光扫描系统的适用性,并实现隧道病害检测的人工智能算法,以提升地铁运营监测效率和病害识别的准确率。结果显示,手持式三维激光扫描系统稳定性相对较低,不适用于地铁隧道病害检测;而轨道移动式三维激光扫描系统可以根据工点里程距离及数量等特征选取合适的测量设备,结合人工智能算法,移动式三维激光扫描系统的全流程病害识别效率提高约28%。

改进的区域生长算法在三维激光点云识别岩体结构面中的应用

交错分布的结构面构成了岩体中的薄弱部位,准确高效的岩体结构面识别和特征信息提取可为岩体稳定性评价提供重要依据。三维激光扫描技术可以极大地提高结构面勘测效率和精度,但目前主流的点云分析算法存在结构面边缘识别模糊、点云分割准确性不能满足结构面特征信息提取精度等问题。因此,考虑岩体结构面点云位置与其邻域的空间关系,利用KD-tree数据结构进行最邻近搜索的体素下采样,在稳健随机Hough变换的基础上改进了区域生长算法,通过多特征值对区域生长分割参数进行修正,依据点云法向量差值和特征终值进行结构面分割,实现了结构面产状、间距、延展度信息的提取。研究结果表明:与传统的主成分分析法和随机抽样一致法相比,在室内块体模型组成的24个结构面中,该方法在相同区域具有更高的识别率和准确率,既能在复杂变化的平面区域保证数据的完整识别,也能在平面的尖锐位置较好地分割边缘点云。利用该方法可以将24个结构面分为6组,并在识别数据中获取对应的结构面特征信息,与实际测量结果相比,角度信息误差约为1°,距离信息误差1cm以内。利用该方法在长江干流蟒蛇寨斜坡岩体中成功识别出3组结构面同时计算各组结构面间距与延展度信息,并采用赤平投影图分析不同结构面组对斜坡稳定性的影响。所提出的方法在室内模型及现场斜坡验证效果良好,可以为岩体结构面识别分割提供稳定且有效的技术支撑。

基于点云数据的预制叠合板尺寸质量智能检测方法

为保证预制叠合板在施工现场能顺利安装,在出厂前通常需要对其进行尺寸质量检测,现有预制叠合板的尺寸质量检测方法难以全面准确地测量叠合板的实际三维尺寸。提出一种基于预制叠合板点云数据的多尺寸质量智能检测方法。对采集的点云数据进行预处理后,利用机器学习算法完成预制叠合板点云的自动定位与分割;依据不同的检测任务,将目标点云沿不同方向降维,映射为二维灰度图像;利用图像特征检测算法,分别实现叠合板底板的长宽、预留胡子筋的出筋长度与间距及桁架钢筋高度的自动检测;在验证试验中,对3块预制叠合板的点云数据进行尺寸质量检测。结果表明,提出的智能检测方法能全面准确地完成预制叠合板出厂尺寸质量检测,能进一步提高预制叠合板非接触质量检测结果的科学性与精准性。

地下溶洞形态分析与可视化

我国是世界上喀斯特地貌面积分布最广泛的国家之一,岩溶类型繁杂,发育较齐全,占国土面积的1/3。岩溶地区存在的主要地质问题有溶洞、断层和软弱地质带等,其具有隐蔽性、突发性和反复性等特点,已成为南方岩溶地区城市工程建设开拓中面临的主要问题。随着激光扫描设备的不断进步和发展,三维激光扫描技术能在封闭式、环境复杂的空间进行自动化测量,具有操作简单、扫描速度快、高分辨率和高精度等特点,可极大地节约测量时间与成本,现已逐渐适应了更广泛的工程应用领域。使用钻孔式三维激光扫描仪获取地下溶洞空间的三维点云数据,针对精度要求较高的复杂空间结构,可能需要布设多个测站进行不同角度扫描获得全局信息。然后,利用深度学习强大的特征学习能力进行点云配准,通过构建数字化模型,客观真实地反映洞内空间形态特征,这将为设计人员提供更精确的岩溶空间信息,制定安全预防措施计划,确保工程施工有序推进。

大型结冰风洞冰形在线测量系统研制与应用

针对大型结冰风洞试验中结冰生长过程三维冰形连续测量需求,研制了基于激光线扫描成像的冰形在线测量系统,并在中国空气动力研究与发展中心3 m×2 m结冰风洞某型飞机机翼模型结冰试验中得到了实际应用。基于三维标定装置,对系统扫描测量过程中的所有激光平面进行了快速标定,获得了相机参数和激光平面参数。为实现复杂结冰表面激光线的精确提取,将Steger方法与梯度重心法进行了有效结合,实现了激光线亚像素的精确提取,结合标定结果,解算激光线空间三维坐标,进而重建得到结冰冰形整体三维形貌。试验结果表明,冰形在线测量系统重复测量精度仅为0.18 mm,可有效获取不同云雾环境下模型前缘霜冰、明冰以及混合冰生长过程在不同时刻的三维冰形。与商用三维扫描仪的测量结果相比,两者结果吻合良好,整体标准偏差为0.5 mm。

基于三维激光扫描技术的冻结黑土细沟发育模拟

为探究融雪径流与冻结状态对黑土细沟网络发育的影响,该研究开展了冻结与非冻结处理黑土坡面的融雪径流模拟冲刷试验,利用三维激光扫描技术获取多次定时径流冲刷并直至侵蚀形态稳定的坡面点云,结合数字表面模型差异(digital surface model of difference,DoD)微地形变化监测方法与点云逆向工程,获取细沟网络发育过程的侵蚀面积、侵蚀体积、细沟长度和细沟密度等侵蚀参数。结果表明,冻结因素与温度变化对细沟网络发育过程与程度有重要影响:1)冻结处理的黑土坡面更容易发展出细沟网络,达到坡面侵蚀形态基本稳定后的侵蚀面积、侵蚀体积以及侵蚀细沟长度是非冻结处理黑土坡面的291%、557%和437%。2)冻结处理与非冻结处理沿坡面细沟截面形态变化差异明显。冻结坡面细沟交叉时宽深比RW/D快速减小,下切速度加快,随后宽度与深度呈比例稳定增加;非冻结坡面汇水处的R_(W/D)随冲刷次数增加而增大,侧蚀速度加快,其他截面R_(W/D)随着冲刷次数的增加而减小,下切速度加快。3)采用ArcGIS与点云逆向工程模型联合获取的冻结状态下细沟形态参数与发育过程DoD相对误差范围为-12.70%~4.42%,提取精度在95%以上。该联合方法在冻结土体条件下获取细沟参数具有较高精度,可作为土壤侵蚀参数高精度提取的一种手段。

基于三维地形扫描的坡沟系统侵蚀产沙监测方法对比

[目的]阐明不同算法在坡面侵蚀监测中的精度和适用性,进而为土壤侵蚀过程监测算法的选择和构建提供参考。[方法]于黄土丘陵沟壑区典型流域同一自然坡面建立5个小区进行径流冲刷试验,以TLS三维点云数据为基础,通过DEM of difference(DoD)、Cloud to Cloud(C2C)、Cloud to Mesh/Model(C2M)和Multiscale Model to Model Cloud Comparison(M3C2)等方法计算侵蚀产沙量,并分析了不同算法对于侵蚀产沙的监测差异。[结果]不确定性分析结果表明:M3C2平均不确定性最小,C2C,C2M次之,DoD最大。产沙结果表明:大流量(85,70,55 L/min)下,4种算法单场次和累计场次产沙量与实测产沙量之间有显著的线性关系(R 2>0.62,p<0.05),M3C2表现最优;小流量(40,25 L/min)下,单场计算产沙量与实测产沙量之间的线性关系不显著但累计产沙量与实测产沙量之间有显著的线性关系(R 2>0.91,p<0.05),DoD表现最优。侵蚀沉积空间分布特征表明:C2C,M3C2和DoD均能反映梁峁坡和沟谷坡侵蚀发展经历的两个阶段(快速发育和稳定发育),其中M3C2能够检测到细微的地形变化,但在TLS扫描盲区,M3C2由于在法线方向上未找到对应点会出现“空洞”。[结论]M3C2算法更适合监测复杂三维地形,但在扫描盲区仍会失效,未来应改进算法,有助于应对更加复杂和剧烈的地形变化。

三维激光扫描技术在城市轨道交通领域的应用

为验证三维激光扫描技术在城市轨道交通领域初支断面、建筑结构限界、管片姿态、椭圆度等检测项目中的测量精度与作业效率,文章通过新型免标靶三维激光扫描仪搭配相应商用软件与传统全站仪法进行比对。结果表明:在初支断面、建筑结构限界测量时,三维激光扫描技术可满足实际工程需要,在数据完整性和侵限点漏判方面具有一定优势;在管片姿态、椭圆度测量时,三维激光扫描技术可精确地建立三维数据模型,提供真实、准确的管片姿态和椭圆度。通过实验可以看出,三维激光扫描技术在轨道交通工程的优势,为其技术的应用和推广提供了一定参考。

基于修正剑桥模型的堆料质量测量方法研究

针对堆料盘点时工作效率低、结果不准确等问题,研究了一种基于修正剑桥模型的质量测量方法,并通过对小型石英砂堆料进行质量测量实验验证了该方法的可行性。为了提高堆料质量盘点时的工作效率以及测量结果的准确度,基于积分原理,结合修正剑桥模型描述的应力应变关系构建堆料的应力-密度模型,基于薄膜式压力传感器设计密度测量装置,根据储料场中常见堆料的形式设计两种不同的堆料,对两种石英砂堆料分别进行质量测量实验,通过获取堆料不同高度以及径向不同深度处的压力进而得到密度,结合三维激光扫描仪采集到的点云数据得到堆料体积,从而实现堆料质量的测量。实验结果表明,对于质量为92.1 kg和86.1 kg的石英砂堆料,该方法测得结果的相对误差均在4%以下。实验结果证明了该测量方法的可行性,后续可为大型堆料的盘点提供参考,有助于企业进一步进行生产计划安排。

基于粒子群优化BP神经网络的激光扫描投影系统畸变预测方法

为了精准、高效地预测和校正激光扫描投影系统的畸变误差,研究了基于粒子群优化BP神经网络的畸变预测方法。建立了BP神经网络结构,并融合粒子群优化算法对BP神经网络的权值和阈值进行优化,得出基于粒子群优化BP神经网络的激光扫描投影系统投影畸变预测模型。选取距激光扫描投影仪器两米的待投影面上的理论坐标点及各点相应畸变值Δx作为粒子群优化BP神经网络的训练数据集,将待投影面上实际投影位置坐标代入训练好的粒子群优化BP神经网络进行预测得到预测畸变值输出,并与实际畸变值对比,最后,引入Elman神经网络预测模型的预测结果与所研究预测方法进行对比。结果表明:在±30°的全视场扫描投影范围内粒子群优化BP神经网络预测模型的均方根误差为0.0176 mm,解算时间仅需22.4 s,相较于Elman神经网络效率提升78.33%,预测精度及时间明显优于Elman神经网络,可以有效预测激光扫描投影系统的畸变误差。

典型地下空间穿戴式三维激光扫描精度分析

针对三维激光扫描系统在地下空间测量不同场景的测量精度及其适宜性分析不够系统和全面的问题,提出一种典型地下空间穿戴式三维激光扫描系统:使用穿戴式三维激光扫描系统采集3种典型地下空间的三维点云数据,并制作典型地下空间平面图;然后通过实测数据验证穿戴式三维激光扫描系统在典型地下空间的测量精度,并分析其适用性。结果表明,穿戴式三维激光扫描系统获取的地下空间点云数据平面及高程精度均优于3 cm,可满足3种典型地下空间场景测量精度要求,能够提高生产效率,获得较好的应用效果。

Design and experiment of variable rate orchard sprayer based on laser scanning sensor

During different growth periods,canopy size and density in orchards are variable,which need application conditions(flow rate and air flow)to be adjusted to match the canopy’s characteristics.In order to improve orchard sprayer’s automatic operating performance,an automatic variable-rate orchard sprayer(VARS)fixed with 40 electromagnetic valves and 8 brushless fans was developed based on the canopy’s spatial dimensions.Each solenoid valve and brushless motor can be individually adjusted in real-time through pulse width modulation(PWM)signals emitted by a control system to adjust each nozzle’s spout and fan rotation speed.A high-precision laser scanning sensor(light detecting and ranging,LIDAR)was adopted as the detector to measure the canopy volume using the variable rate algorithm principle.Field experiments were conducted in an apple orchard,and conventional air blast sprayer(CABS)and directed air-jet sprayer(DAJS)were tested as a comparison.Results showed that on average,46%less spraying solution was applied compared to conventional applications,while penetration rate was similar to DAJS.Normalized deposition in the canopy with variable application was higher than that of conventional applications,indicating that electronic sprayers are more efficient than conventional sprayers.It was also observed that VARS could significantly reduce off-target loss.The field experiment showed that the newly developed variable-rate sprayer can greatly reduce pesticide use and protect the environment for the orchard fruit production,and also provide a reference for design and performance optimization for plant protection machinery.