scholarly journals LASER SCANNING AND POINT CLOUD SEGMENTATION FOR CONTACTLESS GEO-MECHANICAL SURVEYING: CONSERVATIVE RESTORATION IN HYPOGEUM ENVIRONMENT

2021 ◽  
Vol XLVI-M-1-2021 ◽  
pp. 455-461
Author(s):  
F. Mugnai
Keyword(s):  
Rock Mass ◽  
Point Cloud ◽  
Laser Scanning ◽  
Coating Materials ◽  
Point Cloud Segmentation ◽  
Survey Technique ◽  
Advanced Analysis ◽  
Scan Line ◽  
Conservative Restoration ◽  
The Military

Abstract. The work presents a survey campaign specifically designed to formulate an effective restoration project in a Cultural Heritage context, the Military Shrine in Cima Grappa (Italy). Several outputs have been generated by exploring the most advanced laser scanning survey technique and some specific point cloud analysis algorithms. A detailed geometrical 3D reconstruction of human-made and natural tunnels coating materials, a geo-mechanical survey of the rock mass, a map of rock collapses and cinematic analysis of instability processes.Integrating Laser Scanning technique with the Scan-line survey allowed to perform advanced analysis and rock-mass characterisation in a predominant subterranean developed area. Most of the tunnels and underground spaces displayed rock collapses and diffuse active instability processes that certainly could have drastically slowed down surveys and analysis. The adopted techniques allowed both to proceed in acquiring data end in delivering sound outputs rapidly.

scholarly journals Exploiting a Semi-Automatic Point Cloud Segmentation Method to Improve the Quality of Rock-Mass Characterization. The Cima Grappa Conservative Restoration Case Study

2021 ◽  
Vol 10 (5) ◽  
pp. 276
Author(s):  
Francesco Mugnai ◽  
Paolo Farina ◽  
Grazia Tucci
Keyword(s):  
Rock Mass ◽  
Point Cloud ◽  
Laser Scanning ◽  
Automatic Segmentation ◽  
Point Clouds ◽  
Segmentation Method ◽  
Rock Mass Characterization ◽  
Point Cloud Segmentation ◽  
Conservative Restoration ◽  
The Military

This paper presents results from applying semi-automatic point cloud segmentation methods in the underground tunnels within the Military Shrine’s conservative restoration project in Cima Grappa (Italy). The studied area, which has a predominant underground development distributed in a network of tunnels, is characterized by diffuse rock collapsing. In such a context, carrying out surveys and other technical operations are dangerous activities. Considering safety restrictions and unreachable impervious tunnels, having approached the study area with the scan-line survey technique resulted in only partial rock mass characterization. Hence, the geo-mechanical dataset was integrated, applying a semi-automatic segmentation method to the point clouds acquired through terrestrial laser scanning (TLS). The combined approach allowed for remote performance of detailed rock mass characterization, even remotely, in a short time and with a limited operators presence on site. Moreover, it permitted extending assessing tunnels’ stability and state of conservation to the inaccessible areas.

scholarly journals INTEGRATING LASER SCANNING AND GEO-MECHANICAL SURVEY IN CONSERVATIVE RESTORATION; THE CASE OF FIRST WORLD WAR’S CIMA GRAPPA MILITARY SHRINE, ITALY.

2021 ◽  
Author(s):  
Francesco Mugnai ◽  
Paolo Farina ◽  
Grazia Tucci
Keyword(s):  
Rock Mass ◽  
Laser Scanning ◽  
General Description ◽  
Coating Materials ◽  
Restoration Project ◽  
Rock Mass Characterization ◽  
The One ◽  
Conservative Restoration ◽  
The Military ◽  
First World

The work presents results obtained performing a survey campaign specifically designed to formulate an effective restoration project in a critical context. Within the remarkable project, promoted and financed by the Italian Presidency of the Council of the Ministers, and the Italian Ministry of Defence, for designing the conservative restoration plan of the Military Shrine in Cima Grappa (Italy), the assessment of the overall tunnels’ stability and a report of the state of conservation of the underground area has been produced. Exploiting the most advanced laser scanning survey technique, and some specific algorithms for point cloud analysis, several outputs have been generated, in particular a detailed geometrical 3D reconstructions of man-made and natural tunnels coating materials, geo-mechanical survey of rock mass, map of rock collapses and cinematic analysis of instability processes. The integration of Laser Scanning technique with the most commonly used Scan-line survey for rock-mass characterization and architectural surveys, allowed to perform advances analysis even in a high-risk study area as the one considered in the restoration project, which is represented by a predominant subterranean development. Most of the tunnels and underground spaces, displayed rock collapses and diffuse active instability processes that certainly could have drastically slowed down surveys and analysis. The adopted techniques allowed to rapidly proceed in acquiring data end to deliver sound outputs. This paper aims to report both a general description of the project, spending some words on the historical value of the place and describing the complex environment of work, and a detailed depiction of the performed survey activities with particular attention in showing laser scanning survey and the obtained results.

scholarly journals Concrete Spalling Detection for Metro Tunnel from Point Cloud Based on Roughness Descriptor

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Hangbin Wu ◽  
Xingran Ao ◽  
Zhuo Chen ◽  
Chun Liu ◽  
Zeran Xu ◽  
...  
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Point Clouds ◽  
Projected Area ◽  
Roughness Analysis ◽  
Bolt Holes ◽  
Scan Line ◽  
Metro Tunnel ◽  
Area Classification ◽  
Line Fitting

Automatic concrete spalling detection has become an important issue for metro tunnel examinations and maintenance. This paper focuses on concrete spalling detection research with surface roughness analysis based on point clouds produced by 3D mobile laser scanning (MLS) system. In the proposed method, at first, the points on ancillary facilities attached to tunnel surface are considered as outliers and removed via circular scan-line fitting and large residual error filtering. Then, a roughness descriptor for the metro tunnel surface is designed based on the triangulated grid derived from point clouds. The roughness descriptor is generally defined as the ratio of surface area to the projected area for a unit, which works well in identifying high rough areas on the tunnel surface, such as bolt holes, segment seams, and spalling patches. Finally, rough area classification based on Hough transformation and similarity analysis is performed on the identified areas to accurately label patches belonging to segment seams and bolt holes. After removing the patches of bolt holes and segment seams, the remaining patches are considered as belonging to concrete spalling. The experiment was conducted on a real tunnel interval in Shanghai. The result of concrete spalling detection revealed the validity and feasibility of the proposed method.

Comparing traditional geomechanical and remote sensing techniques for rock mass characterization 

2021 ◽  
Author(s):  
Angela Caccia ◽  
Biagio Palma ◽  
Mario Parise
Keyword(s):  
Rock Mass ◽  
Point Cloud ◽  
Laser Scanning ◽  
Quantitative Description ◽  
Present Contribution ◽  
Rock Mass Characterization ◽  
Rock Face ◽  
Remote Sensing Techniques ◽  
The Stability ◽  
Processing Techniques

<p>Analysis of the stability conditions of rock masses starts from detailed geo-structural surveys based on a systematic and quantitative description of the systems of discontinuities. Traditionally, these surveys are performed by implementing the classical geomechanical systems, available in the scientific literature since several decades, through the use of simple tools such as the geological compass to measure dip and dip direction directly on the discontinuity systems, and to fully describe their more significant physical characteristics (length, spacing, roughness, persistence, aperture, filling, termination, etc.). In several cases, this can be difficult because the discontinuities, or even the rock face, cannot be easily accessible. To have a complete survey, very often the involvement of geologists climbers is required, but in many situations this work is not easy to carry out, and in any case it does not cover the whole rock front.</p><p>Today, to solve these problems, traditional geomechanical surveying is implemented by innovative remote techniques using, individually or in combination, instruments such as terrestrial laser scanners and unmanned aerial vehicles to build a point cloud.</p><p>This latter permits to extract very accurate data on discontinuities for stability analyses, based on areal and non-point observations. In addition, the point cloud allows to map sub-vertical walls in their entirety in much shorter times than traditional surveying.</p><p>At this regard, two rock slopes were detected in the Sorrento Peninsula (Campania, southern Italy) with techniques that include traditional mapping, dictated by the guidelines of the International Society for Rock Mechanics, and the remote survey, through laser scanning and drone photogrammetry. The data obtained were processed automatically and manually through the Dips, CloudCompare and Discontinuity Set Extractor softwares.</p><p>In the present contribution we highlight the limits and advantages of the main data collection and the processing techniques, and provide an evaluation of the software packages currently available for the analysis and evaluation of discontinuities, in order to obtain a better characterization of the rock mass.</p>

scholarly journals Point-cloud segmentation of individual trees in complex natural forest scenes based on a trunk-growth method

2021 ◽  
Author(s):  
Qianwei Liu ◽  
Weifeng Ma ◽  
Jianpeng Zhang ◽  
Yicheng Liu ◽  
Dongfan Xu ◽  
...  
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Plant Morphology ◽  
Natural Forest ◽  
Normal Vector ◽  
Natural Forests ◽  
Individual Tree ◽  
Single Tree ◽  
Point Cloud Segmentation ◽  
Individual Trees

AbstractForest resource management and ecological assessment have been recently supported by emerging technologies. Terrestrial laser scanning (TLS) is one that can be quickly and accurately used to obtain three-dimensional forest information, and create good representations of forest vertical structure. TLS data can be exploited for highly significant tasks, particularly the segmentation and information extraction for individual trees. However, the existing single-tree segmentation methods suffer from low segmentation accuracy and poor robustness, and hence do not lead to satisfactory results for natural forests in complex environments. In this paper, we propose a trunk-growth (TG) method for single-tree point-cloud segmentation, and apply this method to the natural forest scenes of Shangri-La City in Northwest Yunnan, China. First, the point normal vector and its Z-axis component are used as trunk-growth constraints. Then, the points surrounding the trunk are searched to account for regrowth. Finally, the nearest distributed branch and leaf points are used to complete the individual tree segmentation. The results show that the TG method can effectively segment individual trees with an average F-score of 0.96. The proposed method applies to many types of trees with various growth shapes, and can effectively identify shrubs and herbs in complex scenes of natural forests. The promising outcomes of the TG method demonstrate the key advantages of combining plant morphology theory and LiDAR technology for advancing and optimizing forestry systems.

scholarly journals MLS POINT CLOUD SEGMENTATION BASED ON FEATURE POINTS OF SCANLINES

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1007-1013
Author(s):  
R. Honma ◽  
H. Date ◽  
S. Kanai
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Point Clouds ◽  
Spatial Distance ◽  
Feature Points ◽  
Segmentation Method ◽  
Point Reduction ◽  
Point Cloud Segmentation ◽  
Edge Points ◽  
The Difference

<p><strong>Abstract.</strong> Point clouds acquired using Mobile Laser Scanning (MLS) are applied to extract road information such as curb stones, road markings, and road side objects. In this paper, we present a scanline-based MLS point cloud segmentation method for various road and road side objects. First, end points of the scanline, jump edge points, and corner points are extracted as feature points. The feature points are then interpolated to accurately extract irregular parts consisting of irregularly distributed points such as vegetation. Next, using a point reduction method, additional feature points on a smooth surface are extracted for segmentation at the edges of the curb cut. Finally, points between the feature points are extracted as flat segments on the scanline, and continuing feature points are extracted as irregular segments on the scanline. Furthermore, these segments on the scanline are integrated as flat or irregular regions. In the extraction of the feature points, neighboring points based on the spatial distance are used to avoid being influenced by the difference in the point density. Based on experiments, the effectiveness of the proposed method was indicated based on an application to an MLS point cloud.</p>

Automatic extraction of rock mass discontinuity based on 3D laser scanning

2020 ◽  
Vol 54 (1) ◽  
pp. qjegh2020-054
Author(s):  
Na Chen ◽  
Xiaoming Cai ◽  
Shu Li ◽  
Xiaobo Zhang ◽  
Qinghui Jiang
Keyword(s):  
Rock Mass ◽  
Point Cloud ◽  
Laser Scanning ◽  
Reproducible Research ◽  
Normal Vector ◽  
Automatic Extraction ◽  
Cloud Data ◽  
Plane Extraction ◽  
Data Source ◽  
Ransac Algorithm

Discontinuity information is important in evaluating the security of a rock mass for the distribution of discontinuity spacings, which affects the mechanical properties and stability of the rock mass. Numerous studies have been conducted on the semi-automatic or automatic extraction of discontinuities from point cloud data. We developed a random sample consensus discontinuity detection (RANSAC) method to automatically extract discontinuities in a rock mass. The proposed method is entirely based on a raw point instead of a triangular mesh, which can retain the integrity of the data. A modified RANSAC algorithm is used to increase the degree of automation. The proposed approach consists of four steps: (1) calculation of the normal vector of the point cloud; (2) plane extraction using the modified RANSAC algorithm; (3) delineation of the boundary of the discontinuity using the modified Graham scan algorithm; and (4) calculation of the orientation and area on the basis of the normal vector and the boundary of the discontinuity. The results and the raw data source are freely provided for reproducible research and to develop the method further.

scholarly journals POINT CLOUD ANALYSIS FOR CONSERVATION AND ENHANCEMENT OF MODERNIST ARCHITECTURE

2017 ◽  
Vol XLII-2/W3 ◽  
pp. 71-77 ◽  
Author(s):  
M. Balzani ◽  
F. Maietti ◽  
B. Mugayar Kühl
Keyword(s):  
Cultural Heritage ◽  
Point Cloud ◽  
Laser Scanning ◽  
Cloud Model ◽  
Geometric Model ◽  
Laser Scanner ◽  
Surface Characteristics ◽  
3D Modelling ◽  
Advanced Analysis ◽  
Acquisition Processes

Documentation of cultural assets through improved acquisition processes for advanced 3D modelling is one of the main challenges to be faced in order to address, through digital representation, advanced analysis on shape, appearance and conservation condition of cultural heritage. 3D modelling can originate new avenues in the way tangible cultural heritage is studied, visualized, curated, displayed and monitored, improving key features such as analysis and visualization of material degradation and state of conservation. An applied research focused on the analysis of surface specifications and material properties by means of 3D laser scanner survey has been developed within the project of Digital Preservation of FAUUSP building, Faculdade de Arquitetura e Urbanismo da Universidade de São Paulo, Brazil. The integrated 3D survey has been performed by the DIAPReM Center of the Department of Architecture of the University of Ferrara in cooperation with the FAUUSP. The 3D survey has allowed the realization of a point cloud model of the external surfaces, as the basis to investigate in detail the formal characteristics, geometric textures and surface features. The digital geometric model was also the basis for processing the intensity values acquired by laser scanning instrument; this method of analysis was an essential integration to the macroscopic investigations in order to manage additional information related to surface characteristics displayable on the point cloud.

scholarly journals Automated Reconstruction of Parametric BIM for Bridge Based on Terrestrial Laser Scanning Data

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Guocheng Qin ◽  
Yin Zhou ◽  
Kaixin Hu ◽  
Daguang Han ◽  
Chunli Ying
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Point Clouds ◽  
Facility Management ◽  
Information Modeling ◽  
Geometric Features ◽  
Unit Structure ◽  
Point Cloud Segmentation ◽  
Reconstruction Quality ◽  
Building Information

Building information modeling (BIM) in industrialized bridge construction is usually performed based on initial design information. Differences exist between the model of the structure and its actual geometric dimensions and features due to the manufacturing, transportation, hoisting, assembly, and load bearing of the structure. These variations affect the construction project handover and facility management. The solutions available at present entail the use of point clouds to reconstruct BIM. However, these solutions still encounter problems, such as the inability to obtain the actual geometric features of a bridge quickly and accurately. Moreover, the created BIM is nonparametric and cannot be dynamically adjusted. This paper proposes a fully automatic method of reconstructing parameterized BIM by using point clouds to address the abovementioned problems. An algorithm for bridge point cloud segmentation is developed; the algorithm can separate the bridge point cloud from the entire scanning scene and segment the unit structure point cloud. Another algorithm for extracting the geometric features of the bridge point cloud is also proposed; this algorithm is effective for partially missing point clouds. The feasibility of the proposed method is evaluated and verified using theoretical and actual bridge point clouds, respectively. The reconstruction quality of BIM is also evaluated visually and quantitatively, and the results show that the reconstructed BIM is accurate and reliable.

Geomechanical characterization of rock masses by means of remote sensing techniques

2020 ◽  
Author(s):  
Lidia Loiotine ◽  
Marco La Salandra ◽  
Gioacchino Francesco Andriani ◽  
Giovanni Barracane ◽  
Marc-Henri Derron ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Rock Mass ◽  
Point Cloud ◽  
Laser Scanning ◽  
Mitigation Measures ◽  
Rock Masses ◽  
Testing Procedures ◽  
Remote Sensing Techniques

&lt;p&gt;Improving the methods for the characterization of rock masses by integrating traditional field surveys with remote sensing techniques is fundamental for practical and realistic discontinuous modelling, in order to identify the failures and kinematics, develop landslide susceptibility assessment and plan prevention and mitigation measures.&lt;/p&gt;&lt;p&gt;A 20 m-high cliff at Polignano a Mare (Southern Italy) was selected as case study for the presence of well-developed discontinuities (bedding and joints) and due to the local morphology, consisting of a valley with opposite slopes at a distance of 150 m, and a pocket beach at their toe. This configuration allowed to perform both traditional and remote sensing surveys. First, photogrammetry methods were carried out on the ground and with the help of a boat. Structure from Motion (SfM) technique was then used to process and combine the pictures, in order to elaborate a raw point cloud of the case study. Secondly, high resolution Terrestrial Laser Scanning (TLS) and Unmanned Aerial Vehicle (UAV) techniques were conducted after positioning Ground Control Points (GCPs) all over the rock mass, with the aim of obtaining a more detailed point cloud. Eventually, a unique and optimized georeferenced point cloud was obtained by combining the previous models, also removing the non-geological objects. Furthermore, Infrared Thermography (IT) was carried out in order to investigate the fracture pattern, the areas of concentrated stress, and the presence of humidity and voids.&lt;/p&gt;&lt;p&gt;The structural analysis of the rock mass was performed directly on the point cloud, by testing procedures and algorithms for the automatic identification of discontinuity sets and of their orientation, spacing, persistence and roughness.&lt;/p&gt;&lt;p&gt;The next step of this research will concern the evaluation of the instability mechanisms with the help of kinematic analyses, by means of stereographic projections. Finally, the reliability of the procedure for a complete rock mass characterization, which is expected to be obtained as the final result, will be tested by means of numerical stability solutions, after calibrating the geomechanical model and importing the fracture system in an appropriate software.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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