Damage Detection on Structures Using Texture Mapped Laser Point Clouds

AIM: We will present how virtual laser scanning (VLS), i.e., simulation of realistic LiDAR campaigns, can be key for applying machine/deep learning (ML/DL) approaches to geographic point clouds. Recent results will be shown for semantic classification and change analysis in multitemporal point clouds using exclusively open source scientific software.MOTIVATION: Laser scanning is able to deliver precise 3D point clouds which have made huge progress in research in geosciences over the last decade. Capturing multitemporal (4D: 3D + time) point clouds enables to observe and quantify Earth surface process activities, their complex interactions and triggers. Due to the large size of 3D/4D datasets that can be captured by modern systems, automatic methods are required for point cloud analysis. Machine learning approaches applied to geographic point clouds, in particular DL, have shown very promising results for many different geoscientific applications [1,2].METHODS & RESULTS: While new approaches for deep neural networks are rapidly developing [1], the bottleneck of sufficient and appropriate training data (typically annotated point clouds) remains the major obstacle for many applications in geosciences. Those data hungry learning methods depend on proper domain representation by training data, which is challenging for natural surfaces and dynamics, where there is high intra-class variability. Synthetic LiDAR point clouds generated by means of VLS, e.g., with the open-source simulator HELIOS++ [3], can be a possible solution to overcome the lack of training data for a given task. In a virtual 3D/4D scene representing the target surface classes, different LiDAR campaigns can be simulated, with all generated point clouds being automatically annotated. VLS software like HELIOS++ allows to simulate any LiDAR platform and settings for a given scene, which offers high potential for data augmentation and the creation of training samples tailored to specific applications. In recent experiments [1], purely synthetic training data could achieve similar performances to costly labeled training data from real-world acquisitions for semantic scene classification.Furthermore, surface changes can be introduced to create dynamic VLS scenes (e.g., erosion, accumulation, movement/transport). Combining LiDAR simulation with automatic change analysis, such as offered by the open-source scientific software py4dgeo [5], enables to perform ML for change analysis in multitemporal point clouds [6]. Recent results show that rockfall activity mapping and classification for permanent laser scanning data can be successfully implemented by combining HELIOS++, py4dgeo and the open-source framework VL3D, which can be used for investigating various ML/DL approaches in parallel.CONCLUSION: Expert domain knowledge (i.e., definition of proper 3D/4D scenes) and the power of AI can be closely coupled in VLS-driven ML/DL approaches to analyze 3D/4D point clouds in the geosciences. Open-source scientific software already offers all required components (HELIOS++, VL3D, py4dgeo). REFERENCES:[1] Esmorís Pena, A. M., et al. (2024): Deep learning with simulated laser scanning data for 3D point cloud classification. ISPRS Journal of Photogrammetry and Remote Sensing. under revision.[2] Winiwarter, L., et al. (2022): DOI: https://doi.org/10.1016/j.rse.2021.112772 [3] HELIOS++: https://github.com/3dgeo-heidelberg/helios[4] VL3D framework: https://github.com/3dgeo-heidelberg/virtualearn3d[5] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo[6] Zahs, V. et al. (2023): DOI: https://doi.org/10.1016/j.jag.2023.1034

In recent years, due to the significant advancements in hardware sensors and software technologies, 3D environmental point cloud modeling has gradually been applied in the automation industry, autonomous vehicles, and construction engineering. With the high-precision measurements of 3D LiDAR, its point clouds can clearly reflect the geometric structure and features of the environment, thus enabling the creation of high-density 3D environmental point cloud models. However, due to the enormous quantity of high-density 3D point clouds, storing and processing these 3D data requires a considerable amount of memory and computing time. In light of this, this paper proposes a real-time 3D point cloud environmental contour modeling technique. The study uses the point cloud distribution from the 3D LiDAR body frame point cloud to establish structured edge features, thereby creating a 3D environmental contour point cloud map. Additionally, unstable objects such as vehicles will appear during the mapping process; these specific objects will be regarded as not part of the stable environmental model in this study. To address this issue, the study will further remove these objects from the 3D point cloud through image recognition and LiDAR heterogeneous matching, resulting in a higher quality 3D environmental contour point cloud map. This 3D environmental contour point cloud not only retains the recognizability of the environmental structure but also solves the problems of massive data storage and processing. Moreover, the method proposed in this study can achieve real-time realization without requiring the 3D point cloud to be organized in a structured order, making it applicable to unorganized 3D point cloud LiDAR sensors. Finally, the feasibility of the proposed method in practical applications is also verified through actual experimental data.

In civil engineering, health monitoring of structure have been treated as an important subject. Health monitoring by using experimental measurements such as strain, acceleration, velocity, displacement, rotation and other parameters has been used for detecting changes, which may indicate damage or degradation. In recent, the applications of health monitoring of large structure have been facilitated by the developments in measurement, communications and computational technology gradually. Especially, large civil structures as bridges are damaged by fatigue loads or unexpected load such as earthquakes and finally reach to failure. Thus, a structural health monitoring and damage detection methods have been developed and attracted a great deal of public attention in recent decades. Actually many research efforts have been conducted to develop a health monitoring and damage detection techniques of existing civil structures. However, these methods are needed to improve to apply to a real civil structure. The purpose of this study is to develop a practical instrument to identify dynamic parameters of real civil structural systems.

3D vehicle shape completion is a key task in urban environment reconstruction, since the available sensors and 3D scanning procedures (such as Mobile Laser Scanning) in an outdoor city scene cannot usually extract the entire car shapes, which can be necessary for specifying their geometric properties for further analysis or realistic visualization. In this paper, we propose a novel multi-view based 3D object point cloud completion technique. In contrast to existing approaches, our method operates on 2D images formed by projecting the point cloud from several virtual camera positions around the object of interest. Both color and geometrical information is considered during the process, generating dense textured point clouds, displaying realistic patterns in the missing regions from the partial inputs. We present both quantitative and qualitative tests on various synthetic and real laser scanned vehicle point clouds, which demonstrate that our method surpasses existing state-of-the-art approaches. By applying it to vehicles from the Shapenet dataset, our approach outperforms recent techniques in terms of Earth Mover’s Distance (EMD) and Chamfer Distance (CD) by 43.8% and 12.17%, respectively.

Slope instability in landslide prone area is a costly problem, which can lead to travel disruption, property damages, and injury or loss of life. For many years, slope monitoring activities are largely carried out by conventional survey instruments such as Total Station, levelling and Global Positioning System (GPS). However, these techniques is a time consuming, hazardous, and costly process, and it can be difficult to ensure that problems are recorded and handled in a consistent manner. Terrestrial laser scanners (TLS) find rapidly growing interest in remote sensing and photogrammetry field as efficient tools for fast and reliable three-dimensional (3D) point cloud data acquisition. The TLS technology is based on the reflectorless and contactless acquisition of a point cloud of the topography using the time-of-flight distance measurement of an infrared laser pulse. This paper describes the capabilities of TLS in slope mapping studies. The main objective of this study is to evaluate the slope mapping pattern at different resolution. This study has been conducted at Cameron Highland, Malaysia, which approximately located at latitude 4d26'36" and longitude 101d23'4". Several data acquisitions on selected cut slopes were performed using the Topcon GLS1500 laser scanner. Ground control points were established using Real Time Kinematic GPS to provide a local coordinate system on laser scanning data. Resolution of a laser scanner determines a density of point cloud during data acquisition. In this experiment, there is a different number of resolution has been set during data acquisition in order to evaluate the result of slope mapping pattern. It was found that, resolution gives an effect in slope mapping pattern.

Recently, terrestrial laser scanners have been significantly improved in terms of accuracy, measurement distance, measurement speed, and resolution. They enable us to capture dense 3D point clouds of large-scale objects and fields, such as factories, engineering plants, large equipment, and transport ships. In addition, the mobile mapping system, which is a vehicle equipped with laser scanners and GPSs, can be used for capturing large-scale point clouds from a wide range of roads, buildings, and roadside objects. Large-scale point clouds are useful in a variety of applications, such as renovation and maintenance of facilities, engineering simulation, asset management, and 3D mapping. To realize these applications, new techniques must be developed for processing large-scale point clouds. So far, point processing has been studied mainly for relatively small objects in the field of computer-aided design and computer graphics. However, in recent years, the application areas of point clouds are not limited to conventional domains, but also include manufacturing, civil engineering, construction, transportation, forestry, and so on. This is because the state-of-the-art laser scanner can be used to represent large objects or fields as dense point clouds. We believe that discussing new techniques and applications related to large-scale point clouds beyond the boundaries of traditional academic fields is very important.This special issue addresses the latest research advances in large-scale point cloud processing. This covers a wide area of point processing, including shape reconstruction, geometry processing, object recognition, registration, visualization, and applications. The papers will help readers explore and share their knowledge and experience in technologies and development techniques.All papers were refereed through careful peer reviews. We would like to express our sincere appreciation to the authors for their submissions and to the reviewers for their invaluable efforts for ensuring the success of this special issue.

In the present paper, Structural health monitoring has become an evolving area of research in last few decades with increasing need of online monitoring the health of large structures. The damage detection by visual inspection of the structure can prove impractical, expensive and ineffective in case of large structures like offshore platforms, multistoried buildings and bridges. Structural health monitoring is defined as the process of detecting damage in a structural system. Damage in the system causes a change in dynamic properties of a system. The structural damage is typically a local phenomenon, which tends to be captured by higher frequency signals. Most of vibration-based damage detection methods require the modal properties that are obtained from measured signals through the system identification techniques. However, the modal properties such as natural frequencies and mode shapes are not such a good sensitive indication of structural damage. Structural damage detection and damage localization of jacket platforms, based on wavelet packet transforms is presented in this paper. Dynamic signals measured from the structure by the finite element software package ANSYS are first decomposed into wavelet packet components. Component energies are then calculated and used for damage assessment. The results show that the WPT-based component energies are good candidate indices that are sensitive to structural damage. These component energies can be used for damage assessment including identifying damage occurrence and location.

first_page settings Order Article Reprints Font Type: Arial Georgia Verdana Font Size: Aa Aa Aa Line Spacing:    Column Width:    Background: Open AccessAbstract Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites † by Jandro L. Abot Department of Mechanical Engineering, The Catholic University of America, Washington, DC 20064, USA † Presented at the 5th International Symposium on Sensor Science (I3S 2017), Barcelona, Spain, 27–29 September 2017. Proceedings 2017, 1(8), 852; https://doi.org/10.3390/proceedings1080852 Published: 4 December 2017 (This article belongs to the Proceedings of Proceedings of the 5th International Symposium on Sensor Science (I3S 2017)) Download Download PDF Download PDF with Cover Download XML Versions Notes Non-destructive evaluation and structural health monitoring techniques can provide frequent or immediate feedback of the condition of a structure including potential damage. However, these techniques cannot detect initiating damage in composite materials with high compaction or multifaceted construction. More critically, they are unable to achieve damage detection without altering the microstructure of the composite material. An alternative method of strain monitoring and damage detection that may offer the advantages of structural health monitoring without their drawbacks consists of using piezoresistive-based carbon nanotube (CNT) yarns integrated in polymers and composite materials. The concept is that the CNT yarns form a continuous sensor circuit and their inherent piezoresistive sensitivity detects strain within the host material through resistance measurements without adding much weight or altering the integrity of the host material. This presentation includes a summary of the piezoresistive response of CNT yarns and the concept and latest experimental results on damage detection in laminated polymeric composite materials and distributed and localized strain measurement. Experimental results also show the ability of a combination of different yarn sensors to detect the exact location and extent of delamination in real time. CNT yarn sensors may provide an adaptive, practical, and sensitive structural health monitoring technique. © 2017 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Share and Cite MDPI and ACS Style Abot, J.L. Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites. Proceedings 2017, 1, 852. https://doi.org/10.3390/proceedings1080852 AMA Style Abot JL. Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites. Proceedings. 2017; 1(8):852. https://doi.org/10.3390/proceedings1080852 Chicago/Turabian Style Abot, Jandro L. 2017. "Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites" Proceedings 1, no. 8: 852. https://doi.org/10.3390/proceedings1080852 Find Other Styles Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here. Article Metrics No No Article Access Statistics Multiple requests from the same IP address are counted as one view.

The complementation of terrestrial laser scanning (TLS) by photogrammetric acquisition techniques enables the exploitation of two different measurement principles. TLS with distance measurements can be used for acquiring large-scale point clouds at medium range distances, while image-based surface reconstruction methods enable flexible acquisition with high precision at short distances. Within this paper, an automatic procedure for the combination of photogrammetry and laser scanning is presented. Synthetic images derived from the laser scanning point clouds are used together with camera images in a common Structure-from-Motion (SfM) process. This enables an automatic registration of multiple laser scans. Furthermore, surface information can also be derived from the imagery using dense image matching methods. While the laser scanning data provides the missing scale information, the imagery can complement the dataset to fill gaps, occlusions or to resolve small details. Consequently, large datasets can be connected by registering imagery and laser scans.

The 3D modeling of urban buildings has become a common research area in various disciplines such as photogrammetry and computer vision, with different applications such as intelligent city management, navigation of self-driving cars and architecture, just to name a few. The objective of this study is to produce a 3D model of the external facade of the buildings with the required precision, accuracy and level of detail according to the user’s requirements, while minimizing time and cost. This research focuses on the production of 3D models for blocks of residential buildings in Tehran, Iran. The Insta 360 One X2 spherical camera is selected to capture the data due to its low cost and 360 × 180° field of view. The camera specifications have facilitated more efficient data collection in terms of both time and cost. The proposed modeling method is based on extracting lines of external walls through the utilization of the point cloud density concept. Initially, photogrammetric point clouds are generated in with a reconstruction precision of 0.24 m from spherical camera images. In the next step, the 3D point cloud is projected into a 2D point cloud by setting the height component to zero. The 2D point cloud is then rotated based on the direction angle determined by the Hough transform so that the perpendicular walls are parallel to the axes of the coordinate system. Next, a 2D point cloud density analysis is performed by voxelizing the point cloud and counting the number of points in each voxel in both the horizontal and vertical directions. By determining the peaks in the density plot, the lines of the external vertical and horizontal walls are extracted. To extract the diagonal external walls, the density analysis is performed in the direction of the first principal component. Finally, by determining the height of each wall in the point cloud, a 3D model is created at the level of detail one. The resulting model has a precision of 0.32 m compared to real sizes, and the 2D plan has a precision of 0.31 m compared to the ground truth map. The use of the spherical camera and point cloud density analysis makes this method efficient and cost-effective, making it a promising approach for future urban modeling projects.

Abstract. The Project ADFEX (Adaptive Federative 3D Exploration of Multi Robot System) pursues the goal to develop a time- and cost-efficient system for exploration and monitoring task of unknown areas or buildings. A fleet of unmanned aerial vehicles equipped with appropriate sensors (laser scanner, RGB camera, near infrared camera, thermal camera) were designed and built. A typical operational scenario may include the exploration of the object or area of investigation by an UAV equipped with a laser scanning range finder to generate a rough point cloud in real time to provide an overview of the object on a ground station as well as an obstacle map. The data about the object enables the path planning for the robot fleet. Subsequently, the object will be captured by a RGB camera mounted on the second flying robot for the generation of a dense and accurate 3D point cloud by using of structure from motion techniques. In addition, the detailed image data serves as basis for a visual damage detection on the investigated building. This paper focuses on our experience with use of a low-cost light-weight Hokuyo laser scanner onboard an UAV. The hardware components for laser scanner based 3D point cloud acquisition are discussed, problems are demonstrated and analyzed, and a quantitative analysis of the accuracy potential is shown as well as in comparison with structure from motion-tools presented.

An adaptive approach for the segmentation and extraction of planar and linear/cylindrical features from laser scanning data

In this paper, the results of an experiment about the vertical accuracy of generated digital terrain models were assessed. The created models were based on two techniques: LiDAR and photogrammetry. The data were acquired using an ultralight laser scanner, which was dedicated to Unmanned Aerial Vehicle (UAV) platforms that provide very dense point clouds (180 points per square meter), and an RGB digital camera that collects data at very high resolution (a ground sampling distance of 2 cm). The vertical error of the digital terrain models (DTMs) was evaluated based on the surveying data measured in the field and compared to airborne laser scanning collected with a manned plane. The data were acquired in summer during a corridor flight mission over levees and their surroundings, where various types of land cover were observed. The experiment results showed unequivocally, that the terrain models obtained using LiDAR technology were more accurate. An attempt to assess the accuracy and possibilities of penetration of the point cloud from the image-based approach, whilst referring to various types of land cover, was conducted based on Real Time Kinematic Global Navigation Satellite System (GNSS-RTK) measurements and was compared to archival airborne laser scanning data. The vertical accuracy of DTM was evaluated for uncovered and vegetation areas separately, providing information about the influence of the vegetation height on the results of the bare ground extraction and DTM generation. In uncovered and low vegetation areas (0–20 cm), the vertical accuracies of digital terrain models generated from different data sources were quite similar: for the UAV Laser Scanning (ULS) data, the RMSE was 0.11 m, and for the image-based data collected using the UAV platform, it was 0.14 m, whereas for medium vegetation (higher than 60 cm), the RMSE from these two data sources were 0.11 m and 0.36 m, respectively. A decrease in the accuracy of 0.10 m, for every 20 cm of vegetation height, was observed for photogrammetric data; and such a dependency was not noticed in the case of models created from the ULS data.

Structural health monitoring, as a non-destructive damage detection technique, has beenadopted by many researchers as well as various industries to keep up with the increasingdemand for preventive maintenance routines. Oil and gas is one of the major industries inwhich effective damage detection can ensure reliable transportation of chemicals andprovide tremendous savings in maintenance costs. The present work investigates theintegrity of a novel damage detection method through a set of experiments conducted ona standard steel pipe commonly used in the oil and gas industry. The methodinvolved collection of the vibration signature of the pipe via certain sensors, anddecomposition of the signature (signals) by empirical mode decomposition. This wasfollowed by the use of a damage index defined on the first intrinsic mode functionresulting from the decomposition. The experiment consisted of a cantilever steelpipe equipped with piezoceramic sensors to monitor the free vibration of a pipeimpacted by an impulse hammer. Three damage cases were studied including singlehalf-circumferential, single full-circumferential, and multiple circumferential andhalf-circumferential damages. A MATLAB code was developed to process and todecompose the signals according to the proposed methodology. The results showed that theproposed damage detection methodology could successfully detect the presence andlocation of damage, and could also identify the severity of the damage. A set ofexperiments was also done to examine the effect of support flexibility on thedamage index, and to examine the sensitivity of the method to support conditions.

PurposeOne of the paramount challenges in the field of structural health monitoring (SHM) is the precise assessment of structural damage. Recently, many methods have been proposed to diagnose damage in structures using time series data. Nevertheless, these techniques are restricted in their ability to capture the bidirectional temporal and spatial relationships among the data. To remedy these shortcomings, this study proposes an advanced deep learning (DL) technique that integrates one-dimensional convolutional neural networks (1DCNN) with bidirectional long short-term memory (BiLSTM) networks, termed BiLSTM-1DCNN.Design/methodology/approachThis study proposes an advanced deep learning (DL) technique that integrates one-dimensional convolutional neural networks (1DCNN) with bidirectional long short-term memory (BiLSTM) networks, termed BiLSTM-1DCNN. The novelty of BiLSTM-1DCNN comes in its effective fusion of 1DCNN’s local feature extraction and BiLSTM’s capacity to capture long-term information from both directions (forward and backward).FindingsValidation using a dataset from the Nam O steel truss bridge demonstrates that the proposed method surpasses conventional models, including 1DCNN (87.9%), LSTM (72.5%), BiLSTM (76.1%) and LSTM-1DCNN (91.1%), achieving an accuracy rate of 96.4%. This approach provides a significant advancement in SHM, paving the way for more accurate and reliable damage detection.Research limitations/implicationsThe study’s limitations include potential overfitting due to the model’s complexity and the high computational resources required. The BiLSTM-1DCNN model’s performance is also influenced by the quality and quantity of the training data as well as the specific characteristics of the dataset. Additionally, while the model performs well in detecting damage in the Nam O steel truss bridge, its generalizability to other types of structures and environmental conditions remains untested.Practical implicationsThe BiLSTM-1DCNN model offers significant practical benefits for structural health monitoring by enhancing damage detection accuracy. Its ability to effectively capture both local features and long-term temporal dependencies makes it a valuable tool for real-time monitoring and early detection of structural issues. This can lead to more timely maintenance actions, potentially reducing repair costs and improving safety. The model’s high accuracy in detecting damage can also support infrastructure management decisions, contributing to better resource allocation and enhanced overall safety of critical structures.Social implicationsThe BiLSTM-1DCNN model’s advanced damage detection capabilities have positive social implications, such as improving the safety and reliability of public infrastructure like bridges. Enhanced structural health monitoring can reduce the risk of catastrophic failures, protecting lives and reducing accidents. By providing more accurate and timely assessments, the model can also lead to more efficient use of maintenance and repairs, ensuring that resources are allocated effectively.Originality/valueThe originality of the BiLSTM-1DCNN model lies in its innovative integration of one-dimensional convolutional neural networks (1DCNN) with bidirectional long short-term memory (BiLSTM) networks. This unique combination leverages 1DCNN’s strength in local feature extraction and BiLSTM’s capacity to capture temporal dependencies in both directions, addressing the limitations of existing methods. The model’s high accuracy in detecting structural damage, as demonstrated by its performance on the Nam O steel truss bridge dataset, highlights its value in advancing structural health monitoring technologies and offers a significant improvement over traditional approaches.