scholarly journals Close-range laser scanning in forests: towards physically based semantics across scales

2018 ◽  
Vol 8 (2) ◽  
pp. 20170046 ◽  
Author(s):  
F. Morsdorf ◽  
D. Kükenbrink ◽  
F. D. Schneider ◽  
M. Abegg ◽  
M. E. Schaepman
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Ground Truth ◽  
Vital Role ◽  
Area Index ◽  
Physically Based ◽  
Laser Systems ◽  
Close Range ◽  
Rich Data ◽  
Information Retrieval Methods

Laser scanning with its unique measurement concept holds the potential to revolutionize the way we assess and quantify three-dimensional vegetation structure. Modern laser systems used at close range, be it on terrestrial, mobile or unmanned aerial platforms, provide dense and accurate three-dimensional data whose information just waits to be harvested. However, the transformation of such data to information is not as straightforward as for airborne and space-borne approaches, where typically empirical models are built using ground truth of target variables. Simpler variables, such as diameter at breast height, can be readily derived and validated. More complex variables, e.g. leaf area index, need a thorough understanding and consideration of the physical particularities of the measurement process and semantic labelling of the point cloud. Quantified structural models provide a framework for such labelling by deriving stem and branch architecture, a basis for many of the more complex structural variables. The physical information of the laser scanning process is still underused and we show how it could play a vital role in conjunction with three-dimensional radiative transfer models to shape the information retrieval methods of the future. Using such a combined forward and physically based approach will make methods robust and transferable. In addition, it avoids replacing observer bias from field inventories with instrument bias from different laser instruments. Still, an intensive dialogue with the users of the derived information is mandatory to potentially re-design structural concepts and variables so that they profit most of the rich data that close-range laser scanning provides.

scholarly journals Mobile Laser Scanning Data for the Evaluation of Pavement Surface Distress

2020 ◽  
Vol 12 (6) ◽  
pp. 942 ◽  
Author(s):  
Maria Rosaria De Blasiis ◽  
Alessandro Di Benedetto ◽  
Margherita Fiani
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Road Traffic ◽  
Single Point ◽  
Three Dimensional ◽  
Point Clouds ◽  
Road Surface ◽  
Important Indicator ◽  
The Road ◽  
Laser Systems

The surface conditions of road pavements, including the occurrence and severity of distresses present on the surface, are an important indicator of pavement performance. Periodic monitoring and condition assessment is an essential requirement for the safety of vehicles moving on that road and the wellbeing of people. The traditional characterization of the different types of distress often involves complex activities, sometimes inefficient and risky, as they interfere with road traffic. The mobile laser systems (MLS) are now widely used to acquire detailed information about the road surface in terms of a three-dimensional point cloud. Despite its increasing use, there are still no standards for the acquisition and processing of the data collected. The aim of our work was to develop a procedure for processing the data acquired by MLS, in order to identify the localized degradations that mostly affect safety. We have studied the data flow and implemented several processing algorithms to identify and quantify a few types of distresses, namely potholes and swells/shoves, starting from very dense point clouds. We have implemented data processing in four steps: (i) editing of the point cloud to extract only the points belonging to the road surface, (ii) determination of the road roughness as deviation in height of every single point of the cloud with respect to the modeled road surface, (iii) segmentation of the distress (iv) computation of the main geometric parameters of the distress in order to classify it by severity levels. The results obtained by the proposed methodology are promising. The procedures implemented have made it possible to correctly segmented and identify the types of distress to be analyzed, in accordance with the on-site inspections. The tests carried out have shown that the choice of the values of some parameters to give as input to the software is not trivial: the choice of some of them is based on considerations related to the nature of the data, for others, it derives from the distress to be segmented. Due to the different possible configurations of the various distresses it is better to choose these parameters according to the boundary conditions and not to impose default values. The test involved a 100-m long urban road segment, the surface of which was measured with an MLS installed on a vehicle that traveled the road at 10 km/h.

3D Measuring of Complex Automotive Parts by Multiple Laser Scanning

2013 ◽  
Vol 371 ◽  
pp. 519-523 ◽  
Author(s):  
Adrian Catalin Voicu ◽  
Ion Gheorghe Gheorghe ◽  
Liliana Laura Badita ◽  
Adriana Cirstoiu
Keyword(s):  
Computer Games ◽  
Laser Scanning ◽  
Three Dimensional ◽  
3D Scanning ◽  
Single Step ◽  
Graph Representation ◽  
Production Environment ◽  
Manufacturing Networks ◽  
Laser Systems ◽  
3D Metrology

Three-dimensional scanning is available for more than 15 years, however there are few that have heard of it and as few people know the applications of this technology. 3D scanning is also known as 3D digitizing, the name coming from the fact that this is a process that uses a contact or non-contact digitizing probe to capture the objects form and recreate them in a virtual workspace through a very dense network of points (xyz) as a 3D graph representation. Based on this information have been developed many new applications in many fields - computer games industry, prosthetics or forensic medicine, the arts and culture area - but the most common area where scanning systems are used remains the automotive industry, aircraft and consumer goods. Most automotive manufacturers currently use 3D metrology based on optical or laser systems to validate products quality. The pieces are initially measured by 3D scanning then they are compared with the designed model (CAD file) using a specialized software. By this comparison producer can interfere very quickly in the manufacturing process to remove the cause of defects, this technique being called Reverse Engineering (RE). The overall accuracy of a 3D acquisition system depends above all on the sensors precision and on the acquisition device (acquisition with contact) or acquisition structure (acquisition without contact). This accuracy may vary from micron to millimeter and the acquisitions size from a few points to several thousand points per second. In a perfect world or in an integrated production environment, 3D measuring systems should be able to measure all the necessary parameters in a single step without errors, and to render the results in the same way to the manufacturing networks equipped with computers, in formats useful for machines control and processes management.

scholarly journals 3D COMPARISON TOWARDS A COMPREHENSIVE ANALYSIS OF A BUILDING IN CULTURAL HERITAGE

2018 ◽  
Vol XLII-2 ◽  
pp. 1061-1066 ◽  
Author(s):  
I. Selvaggi ◽  
M. Dellapasqua ◽  
F. Franci ◽  
A. Spangher ◽  
D. Visintini ◽  
...  
Keyword(s):  
Cultural Heritage ◽  
Point Cloud ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Deformation Analysis ◽  
Point Cloud Data ◽  
Cloud Data ◽  
Site Restoration ◽  
Close Range ◽  
Remote Sensing Techniques

Terrestrial remote sensing techniques, including both Terrestrial Laser Scanning (TLS) and Close-Range Photogrammetry (CRP), have been recently used in multiple applications and projects with particular reference to the documentation/inspection of a wide variety of Cultural Heritage structures.<br> The high density of TLS point cloud data allows to perform structure survey in an unprecedented level of detail, providing a direct solution for the digital three-dimensional modelling, the site restoration and the analysis of the structural conditions. Textural information provided by CRP can be used for the photorealistic representation of the surveyed structure. With respect to many studies, the combination of TLS and CRP techniques produces the best results for Cultural Heritage documentation purposes. Moreover, TLS and CRP point cloud data have been proved to be useful in the field of deformation analysis and structural health monitoring. They can be the input data for the Finite Element Method (FEM), providing some prior knowledge concerning the material and the boundary conditions such as constraints and loading.<br> The paper investigates the capabilities and advantages of TLS and CRP data integration for the three-dimensional modelling compared to a simplified geometric reconstruction. This work presents some results concerning the Baptistery of Aquileia in Italy, characterized by an octagonal plan and walls composed by masonry stones with good texture.

scholarly journals COMPARING 3D DIGITAL TECHNOLOGIES FOR ARCHAEOLOGICAL FIELDWORK DOCUMENTATION. THE CASE OF THESSALONIKI TOUMBA EXCAVATION, GREECE

2021 ◽  
Vol XLVI-M-1-2021 ◽  
pp. 713-720
Author(s):  
A. Stamnas ◽  
D. Kaimaris ◽  
C. Georgiadis ◽  
P. Patias
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Digital Data ◽  
3D Measurement ◽  
Advanced Technologies ◽  
Surface Models ◽  
Historic Structures ◽  
Aerial Vehicle ◽  
Close Range ◽  
Documentation Tool

Abstract. Nowadays, there are many methods and techniques for the documentation and the restoration of historic structures and historical artifacts that are commonly used due to their completeness, accuracy and fastness. The use of advanced 3D measurement technologies, by either using terrestrial or aerial means of acquiring digital data, has become an efficient and reliable documentation tool. Within this context, this study focuses on combining terrestrial laser scanning, unmanned aerial vehicle photogrammetry, close-range photogrammetry and topographic surveying, and comparing the associated digital data for archaeological fieldwork documentation. The data collected during the Thessaloniki Toumba Excavation (Greece) provided accurate digital surface models and photo-realistic three-dimensional outputs of archaeological trenches. The data elaboration enabled new inferences and knowledge to be gained through the implementation of advanced technologies in heritage documentation.

THREE DIMENSIONAL MODELING OF ARCHAEOLOGICAL ARTIFACT USING PHOTOMODELER SCANNER

2015 ◽  
Vol 75 (10) ◽  
Author(s):  
Ainun Nadzirah Abdul Raof ◽  
Halim Setan ◽  
Abert Chong ◽  
Zulkepli Majid
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Data Recording ◽  
Dimensional Model ◽  
Stereo Images ◽  
Three Dimensional Model ◽  
Scanning Method ◽  
Close Range Photogrammetry ◽  
Archaeological Artifact ◽  
Close Range

This article describes the work of archaeological artifact data recording using close range photogrammetry method. A calibrated stereo camera was used to take the stereo images of the artifacts. Photomodeler Scanner software was used to process the stereo images to produce a three-dimensional model of the artifact. For verification purposes, VIVID 910 laser scanner was used to generate three-dimensional model of the same artifact. The study found that close range photogrammetry method is easy to use, with fast data recording, fast data processing and it is a method which is cheaper than the laser scanning method.

scholarly journals COMBINATION OF TERRESTRIAL LASERSCANNING, UAV AND CLOSE-RANGE PHOTOGRAMMETRY FOR 3D RECONSTRUCTION OF COMPLEX CHURCHES IN GEORGIA

2019 ◽  
Vol XLII-2/W11 ◽  
pp. 753-761 ◽  
Author(s):  
T. Luhmann ◽  
M. Chizhova ◽  
D. Gorkovchuk ◽  
H. Hastedt ◽  
N. Chachava ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Measurement Data ◽  
Point Clouds ◽  
Spatial Reconstruction ◽  
External Conditions ◽  
Close Range ◽  
Residual Errors

<p><strong>Abstract.</strong> In September 2018, photogrammetric images and terrestrial laser scans were carried out as part of a measurement campaign for the three-dimensional recording of several historic churches in Tbilisi (Georgia). The aim was the complete spatial reconstruction with a spatial resolution and accuracy of approx. 1cm under partly difficult external conditions, which required the use of different measurement techniques.</p><p>The local measurement data were collected by two laser scanning campaigns (Leica BLK360 and Faro Focus 3D X330), two UAV flights and two terrestrial image sets. The photogrammetric point clouds were calculated with the SfM programs AgiSoft PhotoScan and RealityCapture taking into account the control points from the Faro laser scan. The mean residual errors from the registrations or photogrammetric evaluations are 4-12mm, depending on the selected software. The best completeness and quality of the resulting 3D model was achieved by using laserscan data and images simultaneously.</p>

scholarly journals Contribution of woody elements to tree level reflectance in boreal forests

Silva Fennica ◽  
2021 ◽  
Vol 55 (5) ◽  
Author(s):  
Nea Kuusinen ◽  
Aarne Hovi ◽  
Miina Rautiainen
Keyword(s):  
Norway Spruce ◽  
Scots Pine ◽  
Forest Floor ◽  
Laser Scanning ◽  
Remote Sensing Data ◽  
Hyperspectral Data ◽  
Tree Level ◽  
Area Index ◽  
Reflectance Model ◽  
Physically Based

Spectral mixture analysis was used to estimate the contribution of woody elements to tree level reflectance from airborne hyperspectral data in boreal forest stands in Finland. Knowledge of the contribution of woody elements to tree or forest reflectance is important in the context of lea area index (LAI) estimation and, e.g., in the estimation of defoliation due to insect outbreaks, from remote sensing data. Field measurements from four Scots pine ( L.), five Norway spruce ( (L.) Karst.) and four birch ( Roth and Ehrh.) dominated plots, spectral measurements of needles, leaves, bark, and forest floor, airborne hyperspectral as well as airborne laser scanning data were used together with a physically-based forest reflectance model. We compared the results based on simple linear combinations of measured bark and needle/leaf spectra to those obtained by accounting for multiple scattering of radiation within the canopy using a physically-based forest reflectance model. The contribution of forest floor to reflectance was additionally considered. The resulted mean woody element contribution estimates varied from 0.140 to 0.186 for Scots pine, from 0.116 to 0.196 for birches and from 0.090 to 0.095 for Norway spruce, depending on the model used. The contribution of woody elements to tree reflectance had a weak connection to plot level forest variables.Pinus sylvestrisPicea abiesBetula pendulaBetula pubescens

scholarly journals Accuracy Evaluation of Videogrammetry Using A Low-Cost Spherical Camera for Narrow Architectural Heritage: An Observational Study with Variable Baselines and Blur Filters

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 496 ◽  
Author(s):  
Zheng Sun ◽  
Yingying Zhang
Keyword(s):  
Laser Scanning ◽  
Low Cost ◽  
Three Dimensional ◽  
Ground Truth ◽  
3D Models ◽  
Accuracy Evaluation ◽  
Architectural Heritage ◽  
Video Frames ◽  
Image Pairs ◽  
Spherical Camera

Three-dimensional (3D) reconstruction using video frames extracted from spherical cameras introduces an innovative measurement method in narrow scenes of architectural heritage, but the accuracy of 3D models and their correlations with frame extraction ratios and blur filters are yet to be evaluated. This article addresses these issues for two narrow scenes of architectural heritage that are distinctive in layout, surface material, and lighting conditions. The videos captured with a hand-held spherical camera (30 frames per second) are extracted to frames with various ratios starting from 10 and increasing every 10 frames (10, 20, …, n). Two different blur assessment methods are employed for comparative analyses. Ground truth models obtained from terrestrial laser scanning and photogrammetry are employed for assessing the accuracy of 3D models from different groups. The results show that the relative accuracy (median absolute errors/object dimensions) of spherical-camera videogrammetry range from 1/500 to 1/2000, catering to the surveying and mapping of architectural heritage with medium accuracy and resolution. Sparser baselines (the length between neighboring image pairs) do not necessarily generate higher accuracy than those from denser baselines, and an optimal frame network should consider the essential completeness of complex components and potential degeneracy cases. Substituting blur frames with adjacent sharp frames could reduce global errors by 5–15%.

scholarly journals Low-Cost Three-Dimensional Modeling of Crop Plants

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2883 ◽  
Author(s):  
Jorge Martinez-Guanter ◽  
Ángela Ribeiro ◽  
Gerassimos G. Peteinatos ◽  
Manuel Pérez-Ruiz ◽  
Roland Gerhards ◽  
...  
Keyword(s):  
Low Cost ◽  
Three Dimensional ◽  
Ground Truth ◽  
Reconstruction Algorithm ◽  
3D Models ◽  
Crop Plants ◽  
Plant Phenotyping ◽  
Area Index ◽  
Ground Truth Data ◽  
The Creation

Plant modeling can provide a more detailed overview regarding the basis of plant development throughout the life cycle. Three-dimensional processing algorithms are rapidly expanding in plant phenotyping programmes and in decision-making for agronomic management. Several methods have already been tested, but for practical implementations the trade-off between equipment cost, computational resources needed and the fidelity and accuracy in the reconstruction of the end-details needs to be assessed and quantified. This study examined the suitability of two low-cost systems for plant reconstruction. A low-cost Structure from Motion (SfM) technique was used to create 3D models for plant crop reconstruction. In the second method, an acquisition and reconstruction algorithm using an RGB-Depth Kinect v2 sensor was tested following a similar image acquisition procedure. The information was processed to create a dense point cloud, which allowed the creation of a 3D-polygon mesh representing every scanned plant. The selected crop plants corresponded to three different crops (maize, sugar beet and sunflower) that have structural and biological differences. The parameters measured from the model were validated with ground truth data of plant height, leaf area index and plant dry biomass using regression methods. The results showed strong consistency with good correlations between the calculated values in the models and the ground truth information. Although, the values obtained were always accurately estimated, differences between the methods and among the crops were found. The SfM method showed a slightly better result with regard to the reconstruction the end-details and the accuracy of the height estimation. Although the use of the processing algorithm is relatively fast, the use of RGB-D information is faster during the creation of the 3D models. Thus, both methods demonstrated robust results and provided great potential for use in both for indoor and outdoor scenarios. Consequently, these low-cost systems for 3D modeling are suitable for several situations where there is a need for model generation and also provide a favourable time-cost relationship.

scholarly journals Important Airborne Lidar Metrics of Canopy Structure for Estimating Snow Interception

2021 ◽  
Vol 13 (20) ◽  
pp. 4188
Author(s):  
Micah Russell ◽  
Jan U. H. Eitel ◽  
Timothy E. Link ◽  
Carlos A. Silva
Keyword(s):  
Laser Scanning ◽  
Mean Squared Error ◽  
Canopy Structure ◽  
Three Dimensional ◽  
Variable Importance ◽  
Airborne Lidar ◽  
Extrinsic Factors ◽  
Area Index ◽  
Wide Range ◽  
Structural Metrics

Forest canopies exert significant controls over the spatial distribution of snow cover. Canopy snow interception efficiency is controlled by intrinsic processes (e.g., canopy structure), extrinsic processes (e.g., meteorological conditions), and the interaction of intrinsic-extrinsic factors (i.e., air temperature and branch stiffness). In hydrological models, intrinsic processes governing snow interception are typically represented by two-dimensional metrics like the leaf area index (LAI). To improve snow interception estimates and their scalability, new approaches are needed for better characterizing the three-dimensional distribution of canopy elements. Airborne laser scanning (ALS) provides a potential means of achieving this, with recent research focused on using ALS-derived metrics that describe forest spacing to predict interception storage. A wide range of canopy structural metrics that describe individual trees can also be extracted from ALS, although relatively little is known about which of them, and in what combination, best describes intrinsic canopy properties known to affect snow interception. The overarching goal of this study was to identify important ALS-derived canopy structural metrics that could help to further improve our ability to characterize intrinsic factors affecting snow interception. Specifically, we sought to determine how much variance in canopy intercepted snow volume can be explained by ALS-derived crown metrics, and what suite of existing and novel crown metrics most strongly affects canopy intercepted snow volume. To achieve this, we first used terrestrial laser scanning (TLS) to quantify snow interception on 14 trees. We then used these snow interception measurements to fit a random forest model with ALS-derived crown metrics as predictors. Next, we bootstrapped 1000 calculations of variable importance (percent increase in mean squared error when a given explanatory variable is removed), keeping nine canopy metrics for the final model that exceeded a variable importance threshold of 0.2. ALS-derived canopy metrics describing intrinsic tree structure explained approximately two-thirds of the snow interception variability (R2 ≥ 0.65, RMSE ≤ 0.52 m3, relative RMSE ≤ 48%) in our study when extrinsic factors were kept as constant as possible. For comparison, a generalized linear mixed-effects model predicting snow interception volume from LAI alone had a marginal R2 = 0.01. The three most important predictor variables were canopy length, whole-tree volume, and unobstructed returns (a novel metric). These results suggest that a suite of intrinsic variables may be used to map interception potential across larger areas and provide an improvement to interception estimates based on LAI.

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