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Long-range terrestrial laser scanning measurements of annual and intra-annual mass balances for Urumqi Glacier No.?1, eastern Tien Shan, China
摘要： The direct glaciological method provides in situ observations of annual or seasonal surface mass balance, but can only be implemented through a succession of intensive in situ measurements of field networks of stakes and snow pits. This has contributed to glacier surface mass-balance measurements being sparse and often discontinuous in the Tien Shan. Nevertheless, long-term glacier mass-balance measurements are the basis for understanding climate–glacier interactions and projecting future water availability for glacierized catchments in the Tien Shan. Riegl VZ?-6000 long-range terrestrial laser scanner (TLS), typically using class 3B laser beams, is exceptionally well suited for repeated glacier mapping, and thus determination of annual and seasonal geodetic mass balance. This paper introduces the applied TLS for monitoring summer and annual surface elevation and geodetic mass changes of Urumqi Glacier No. 1 as well as delineating accurate glacier boundaries for 2 consecutive mass-balance years (2015–2017), and discusses the potential of such technology in glaciological applications. Three-dimensional changes of ice and firn–snow bodies and the corresponding densities were considered for the volume-to-mass conversion. The glacier showed pronounced thinning and mass loss for the four investigated periods; glacier-wide geodetic mass balance in the mass-balance year 2015–2016 was slightly more negative than in 2016–2017. Statistical comparison shows that agreement between the glaciological and geodetic mass balances can be considered satisfactory, indicating that the TLS system yields accurate results and has the potential to monitor remote and inaccessible glacier areas where no glaciological measurements are available as the vertical velocity component of the glacier is negligible. For wide applications of the TLS in glaciology, we should use stable scan positions and in-situ-measured densities of snow–firn to establish volume-to-mass conversion.
关键词： terrestrial laser scanning,glacier mass balance,Tien Shan,geodetic method,Urumqi Glacier No. 1
更新于2025-09-11 14:15:04
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Automated Method of Extracting Urban Roads Based on Region Growing from Mobile Laser Scanning Data
摘要： With the rapid development of three-dimensional point cloud acquisition from mobile laser scanning systems, the extraction of urban roads has become a major research focus. Although it has great potential for digital image processing, the extraction of roads using the region growing approach is still in its infancy. We propose an automated method of urban road extraction based on region growing. First, an initial seed is chosen under constraints relating to the Gaussian curvature, height and number of neighboring points, which ensures that the initial seed is located on a road. Then, the growing condition is determined by the angle threshold of the tangent plane of the seed point. Then, new seeds are selected based on the identi?ed road points and their curvature. The method also includes a strategy for dealing with multiple discontinuous roads in a dataset. The result shows that the method can not only achieve high accuracy in urban road extraction but is also stable and robust.
关键词： road extraction,tangent plane,point cloud,region growing,mobile laser scanning
更新于2025-09-11 14:15:04
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Effect of Sampling Interval and Anisotropy on Laser Scanning Accuracy in Rock Material Surface Roughness Measurements
摘要： Three-dimensional laser scanning is an advanced technique for fracture roughness measurements. The surface roughness of fractures (discontinuities) accurately measured is of practical importance for proper evaluation of the mechanical properties of a fractured rock material. It is also appropriate to perform a more systematic study on the effect of a sampling interval on the roughness measurement accuracy. This effect was investigated based on the 3D-point-cloud data of a fracture surface acquired with laser scanning. A series of 2D profiles corresponding to twelve directions were extracted from concentric circular sampling windows of different diameters. The roughness measurement accuracy is quantified by the three parameters, viz the mean square first derivative Z2 , structure function SF , and roughness profile index R p . The sampling interval effect was investigated for its different values by analyzing the three parameters of different profiles. It was established that SF was very sensitive, while Z2 and R p were less responsive to the sampling interval. It exerts a much weaker influence on the rock material fracture roughness in comparison with anisotropy.
关键词： sampling interval effect,rock material fracture,rock discontinuity,surface roughness,three-dimensional laser scanning
更新于2025-09-11 14:15:04
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The Encyclopedia of Archaeological Sciences || Laser Scanning
摘要： Laser scanning provides archaeology with a high-speed process for the acquisition of three-dimensional (3D) spatial data. The technique provides surface-based 3D measurements of any small- or large-scale, complex, irregular, standard or nonstandard real-world scene. The resulting data are visualized through the production of point clouds, with the final results depicted as line drawings, computer-aided design (CAD) models, 3D surface models, and video animations, acting as an enhanced communication tool that has the ability of visualizing real-world objects in 3D space. It is the most effective way to quickly obtain data from the observed object and it enables measurements of areas that were unable to be collected previously, such as through hand-based drawings or total station surveys.
关键词： point clouds,Laser scanning,CAD models,archaeology,3D spatial data
更新于2025-09-11 14:15:04
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Examining Forest Structure With Terrestrial Lidar: Suggestions and Novel Techniques Based on Comparisons Between Scanners and Forest Treatments
摘要： Terrestrial laser scanners (TLSs) provide a tool to assess and monitor forest structure across forest landscapes. We present TLS methods, suggestions, and mapped guidelines for planning TLS acquisitions at varying scales and forest densities. We examined rates of point-density decline with distance from two TLS that acquire data at relatively high and low point density and found that the rates were nearly identical between scanners (p value <0.01), suggesting that our findings are applicable to a range of TLS types. Using unique, TLS-adapted processing methods, we determined the relative accuracy of TLS-derived plot-scale estimates of tree height, diameter-at-breast-height, height-to-canopy, tree counts, as well as treatment-scale tree density and patch metrics, using both high point density and low point density TLS among thinned and nonthinned forest treatments. The high-density TLS consistently provides more accurate estimates of plot-level metrics (R2 = 0.46 to 0.87) than the low-density TLS (R2 = (cid:1)0.14 to 0.53). At treatment scales, tree density estimates are similar among scanners (R2 = 0.95 vs. 0.71), as are canopy cover and patch metrics. We develop and present the normalized density-distance index (NDDI), which can account for up to 59% of the variance in estimate error and can be used to guide TLS-data acquisition plans. This index indicates whether a given location has generally higher point density (higher NDDI) relative to the distance from the scanner and can be used as a proxy for uncertainty. Using NDDI as a guide for fair comparison between scanners, both plot- and treatment-scale estimates improved.
关键词： NDDI,forest management,point density,forest structure,Terrestrial laser scanning
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - An Approach to Tree Species Classification Using Voxel Neighborhood Density-Based Subsampling of Multiscan Terrestrial Lidar Data
摘要： The knowledge on the species of individual trees is ineluctable for accurate forest parameter estimation and related studies. Terrestrial Laser Scanning (TLS) remote sensing systems acquire a huge number of point samples that contain very accurate and detailed three dimensional (3D) information of tree structures. Every tree species has unique internal and external crown structural characteristics that can be modeled from its TLS data. However, methods in the state of the art show reduced performance due to inaccurate modeling of tree structures such as the crown, and the branch, and poor selection of features. The proposed method leverages on the fine internal and external crown structural information in TLS data to achieve species classification. We remove noise and stem points in TLS data using a novel voxel neighborhood density-based technique. Internal and external crown geometric features derived from the branch level, and the crown level, respectively, are provided to a nonlinear Support Vector Machines (SVM) to achieve species classification, and evaluate feature relevance. All experiments were conducted on a set of 75 manually delineated trees belonging to the Spruce, the Pine, and the Birch species.
关键词： Tree Species,Remote Sensing,Classification,Terrestrial Laser Scanning (TLS),Light Detection and Ranging (LiDAR)
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Discriminative Learning of Point Cloud Feature Descriptors Based on Siamese Network
摘要： It is challenging to direct extract the feature descriptors of the object in the point cloud, although deep learning has been widely used with the classification and detection in the point cloud, those methods hidden feature presentation in the network. Since the point cloud scanned by the Laser Scanner usually have different point density, unordered and even the different occlusion, which go beyond the reach of hand-crafted descriptors, e.g. FPH, FPFH, VFH, ROPS. In this paper, we aim to direct extract the feature descriptors of the point cloud object through the raw point cloud. Inspired by the recent success of the Siamese networks[6], PointNet[7] and PointNet++[8], we propose a novel network to direct extract the feature descriptors of the whole point cloud object. We train our network with the Euclidean distance as the loss function which reflects feature descriptors similarity. The experiment object datasets were acquired by Mobile Laser Scanning (MLS) system which contains 6 categories. Experiment result shows that our network has a robust generalization, which can well direct extract the feature descriptors of the whole point cloud object.
关键词： Point cloud,mobile laser scanning,feature description,siamese network
更新于2025-09-10 09:29:36
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Efficient and robust lane marking extraction from mobile lidar point clouds
摘要： Surveys of roadways with Mobile Laser Scanning (MLS) are now being conducted on a regular basis by many transportation agencies to provide detailed geometric information to support a wide range of applications, including asset management. Most MLS systems provide intensity (return signal strength) data as a point attribute in georeferenced point clouds, which may be used to estimate retro-reflectivity of pavement markings for effective maintenance. Nevertheless, the extraction of pavement markings from mobile lidar data remains an open challenge, due to variable noise, degree of wear on the markings, and road conditions. This paper addresses these challenges, presenting a novel approach for efficient, reliable extraction of lane markings, including those that have been significantly worn. First, using the MLS trajectory information, the lidar data is discretized into smaller sections, and then transformed to the local coordinate system, such that the road surface is near-horizontal for reliable extraction on roads with significant grade. Subsequently, the road surface is extracted using the constrained Random Sampling and Consensus (RANSAC) algorithm and then rasterized into a 2D intensity image to apply image processing techniques, namely: image segmentation to separate the lane markings from the road pavement, and a morphological opening operation to remove small objects. However, the extracted lane markings are prone to over-segmentation, due to occlusions or worn portions caused by moving vehicles. To rectify this, topologically-similar lane markings are associated with each other by computing line parameters (i.e., orientation and distance from the origin), which enables the gaps to be filled among the associated lanes. Finally, the remaining incorrect lane markings are detected and removed through a noise filtering phase using Dip test statistics. Examples of the effectiveness and application of the methodology are shown for a variety of sites with stripes of variable condition to highlight the robustness of the approach. Using optimized parameter values, the algorithm achieved F1 scores of 89–97% when tested on a variety of datasets encompassing a wide range of road scene types.
关键词： Point cloud,Mobile laser scanning,Lane marking extraction
更新于2025-09-10 09:29:36
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Estimation of forest structural and compositional variables using ALS data and multi-seasonal satellite imagery
摘要： Advanced forest resource inventory (FRI) information is of critical importance for sustainable forest management. FRIs are dependent on remote sensing data and processing methods, along with field calibration/validation to generate cost-effective options for modelling forest inventory and biophysical variables over large areas. The objective of this study was to examine the impact of combining multi-seasonal multispectral satellite imagery with airborne laser scanning (ALS) data for estimating basal area, species mixture and stem density for an uneven-aged tolerant hardwood forest in Ontario, Canada. Using random forest (RF) regression as a non-parametric diagnostic technique, three multispectral optical sensors (i.e., Landsat-5 TM, Sentinel-2 A and WorldView-2) were compared to examine the most cost-effective sensor configuration for modelling FRI variables. The contribution of spectral predictors derived from these optical sensors as well as ALS height and intensity metrics were evaluated using RF variable importance. As part of our variable selection framework, all predictor variables were grouped into relatively independent clusters using a hierarchical variable clustering technique, which revealed the distinctiveness between information contained in spectral predictors, height- and intensity-based metrics. This indicates that ALS intensity data carry unique information complementary to passive near-infrared data for forest characterization. ALS data alone did not result in accurate models for basal area and species mixture, but predictive accuracies were improved significantly with the addition of spectral predictors. Compared to single-date images, multi-seasonal imagery proved to be more accurate for modelling FRI variables, especially when combined with ALS data. Despite its limited spatial resolution, Sentinel-2 A was found to be the most cost-effective image source for enhancing ALS-based FRI models. Using variables identified by the variable selection procedure, best subsets regression outperformed the RF models developed for diagnostic analysis, resulting in a suite of accurate and parsimonious predictive models, with coefficients of determination of 0.73, 0.90 and 0.67, for basal area, species mixture, and stem density, respectively.
关键词： Multi-seasonal satellite imagery,Variable selection,Sentinel-2A,Airborne laser scanning (ALS),Forest resource inventory
更新于2025-09-10 09:29:36
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The Evaluation of Static Deficiencies of Lower Limbs with the Use of Non-Contact Measurement
摘要： The purpose of this paper is to develop a procedure of the lower limbs volumetric modelling using the laser measurement arm and the evaluation of defects, which can cause disorders in the field of locomotion. The procedure is presented based on the analysis of two specimens: woman (age 22) and man (age 23), whose lower limbs are fully formed. The method includes the laser scanning and the lower limbs regularity evaluation based on the characteristic lines, which were identified during palpation examination of the skin and bones characteristic points or during the radiological examination. The valgus knee and the knee joint hyperextension were determined for the woman’s case and no deficiencies for the man’s case. Presented procedure has a screening application and can support the rehabilitation process. The advantage is that the developed method is noninvasive and the diagnostics can be performed while muscles are active in the natural standing position. The SL method was verified by the Laser Tracker system. On the group of 55 students with the average age of 10.4 years, the measurements were performed in order to define the influence of BMI on the correctness of the results, which were achieved while using the proposed method of the evaluation of the static deficiencies. No relevant influence of BMI on errors occurring in the determination of defects valgus and varus of the lower limbs.
关键词： Valgus,BMI,Characteristic points,Varus,3D modelling,Baseline,Laser scanning
更新于2025-09-10 09:29:36