A voxel-based fine-scale 3D landscape pattern analysis using laser scanner point clouds

The landscape pattern metrics can quantitatively describe the characteristics of landscape pattern and are widely used in various fields of landscape ecology.Due to the lack of vertical information,2D landscape metrics cannot delineate the vertical characteristics of landscape pattern.Based on the point clouds,a high-resolution voxel model and several voxel-based 3D landscape metrics were constructed in this study and 3D metrics calculation results were compared with that of 2D metrics.The results showed that certain quantifying difference exists between 2D and 3D landscape metrics.For landscapes with different components and spatial configurations,significant difference was disclosed between 2D and 3D landscape metrics.3D metrics can better reflect the real spatial structure characteristics of the landscape than 2D metrics.

Confocal 3D Optical Intraoral Scanners and Comparison of Image Capturing Accuracy

Several capture techniques are used in intraoral optical scanners in the dental market,such as Triangulation(Cerec Omnicam,Dentsply Sirona),Activewave front sampling(3M ESPE)and confocal technology(iTero,Align).The accuracy of intraoral scanners is the most significant focal point for developers to research.This in-vitro study studied the accuracy of confocal scanners launched from 2015-2020(Trios 3,Trios 4,iTero Element;3Shape Trios A/S,Copenhagen,Denmark,and iTero Element2,and iTero Element5D;Align Technologies,San Jose,CA,USA).A 3D printing model modified from the American National Standard No.132 was scanned five times each scanner.Both Trios3 and Trios4 were scanned using regular scan mode(N)and high-resolution mode(HR).All scanning methods followed the recommendations from the manufacturers.Then the digital models were exported and saved as STL files.Various measurements were determined in the digital model from each scan using Rhinoceros 3D Software(Rhino,Robert McNeel&Associates for Windows,Washington DC,USA).Measurements from the 3D printed model were used as control.All data were recorded in Microsoft Excel and then transferred to SPSS.Descriptive statistics were recorded.Multiple comparisons of various measurements were made among the different scanners and with the control using One-way ANOVA and post hoc using Sheffe(p<0.01).The surface area in the X and Y axis ranged from 2–60 mm,while the depth(Z-axis)ranged from 2–8 mm.The Trios and iTero families showed similar accuracy.However,for the diagonal,the Trios series showed better results compared with the iTero series.Within the same brand,different versions showed no significant change regarding accuracy.

The Interventions of Pietro da Cortona in the Crypt of Santa Maria in Via Lata in Rome, Studied through a Morphometric Three-Dimensional Survey

Twenty years after the last archaeological researches and surveys, a new investigation has been carried out on the basement in the church of Santa Maria in Via Lata in Rome. The study has employed three-dimensional surveys with laser scanning methodology and has focused both on archaeological and architectural issues. Indeed, the present layout of the basement derives from a XVII century remodelling of early Christian and medieval spaces planned by Pietro da Cortona. The architect gave a unique setting and composition to the underground spaces, different in shapes and building materials, thanks to the refinement of his baroque language. Though he worked in small spaces with static problems connected to the foundations and to the loads of the church rising above, and with poor lighting and extreme dampness, Pietro da Cortona put skilfully together “modern” elements with ancient or historical pre-existences. The study focuses on Berrettini’s design process through a three-dimensional analysis with CAD systems, starting from the new XVII century fa?ade and from the articulated distribution of routes that led to the intimate underground interiors. Metrical processing gave the possibility to improve the knowledge about room geometry and to confirm the interpretations put forward by major scholars such as Krautheimer and Cavazzi.

3D激光扫描测量开发建设项目堆弃土边坡侵蚀强度的试验研究

为了提高开发建设项目水土保持监测中侵蚀强度测量的效率和精度,尝试使用3D激光扫描仪对排土场堆弃土边坡进行土壤流失量监测,并与常用的测钎法进行比较。结果表明:在同一水土流失坡面同时期的监测中,传统测钎法的监测结果与3D激光扫描法监测的结果偏差为13.26%;3D激光扫描仪具有较高的土壤形态变化记录性能,相对传统的监测方法具有较高的监测精度。

A shoe-box-sized 3D laser nanoprinter based on two-step absorption

State-of-the-art commercially available 3D laser micro-and nanoprinters using polymeric photoresists based on two-or multi-photon absorption rely on high-power pico-or femtosecond lasers,leading to fairly large and expensive instruments.Lately,we have introduced photoresists based on two-step absorption instead of two-photon absorption,allowing for the use of small and inexpensive continuous-wave 405 nm wavelength GaN semiconductor laser diodes with light-output powers below 1 mW.Here,using the identical photoresist system and similar laser diodes,we report on the design,construction,and characterization of a 3D laser nanoprinter that fits into a shoe box.This shoe box contains all optical components,namely the mounted laser,the collimation-and beam-shaping optics,a miniature MEMS xy-scanner,a tube lens,the focusing microscope objective lens(NA=1.4,100×magnification),a piezo slip-stick z-stage,the sample holder,a camera monitoring system,LED sample illumination,as well as the miniaturized control electronics employing a microcontroller.We present a gallery of example 3D structures printed with this instrument.We achieve about 100 nm lateral spatial resolution and focus scan speeds of about 1 mm/s.Potentially,our shoe-box-sized system can be made orders of magnitude less expensive than today’s commercial systems.

RESEARCH ON LASER RANGE SCANNING AND ITS APPLICATION

In this paper the development of the technology of the laser scanning is summarized.The principles of laser range scanning are introduced.Based on the laser scanning technology and methods,which are investigated by the authors to survey deposit volume,a surveying system is developed and a practical application is performed.It is shown that the laser_scanning technology has obvious advantages such as measurement precision,automation and visualization of observed data in comparison with the traditional methods.As a result,labor intensity is relieved obviously and work efficiency is promoted.

Identify Plant Drought Stress by 3D-Based Image

Plants respond to drought stress with different physical manners, such as morphology and color of leaves. Thus, plants can be considered as a sort of living-sensors for monitoring dynamic of soil water content or the stored water in plant body. Because of difficulty to identify the early wilting symptom of plants from the results in 2D （two-dimension） space, this paper presented a preliminary study with 3D （three-dimension）-based image, in which a laser scanner was used for achieving the morphological information of zucchini （Cucurbita pepo） leaves. Moreover, a leaf wilting index （DLWIF） was defined by fractal dimension. The experiment consisted of phase-1 for observing the temporal variation of DLWIF and phase-2 for the validation of this index. During the experiment, air temperature, luminous intensity, and volumetric soil water contents （VSWC） were simultaneously recorded over time. The results of both phases fitted the bisector （line： 1：1） with R2=0.903 and REMS=0.155. More significantly, the influence of VSWC with three levels （0.22, 0.30, and 0.36 cm3 cm-3） on the response of plant samples to drought stress was observed from separated traces of DLWIF. In brief, two conclusions have been made： （i） the laser scanner is an effective tool for the non-contact detection of morphological wilting of plants, and （ii） defined DLWIF can be a promising indicator for a category of plants like zucchini.

3维激光扫描仪定向技术研究

针对3维激光扫描仪无法直接获得目标物表面点的大地坐标的缺点,将全站仪导线测量中的定向技术应用到3维激光扫描仪中;根据扫描技术特点,设计了定向标识;根据定向标识的扫描数据,设计了标识的识别算法,并应用最速下降法进行求解,实现了3维激光扫描仪的定向。

Focus3D三维激光扫描仪测距精度检校试验

为对地面三维激光扫描仪的测距精度进行校准,以Focus3D三维激光扫描仪为例,对其径向距离和空间距离的测量精度进行了检校试验。采用该型三维激光扫描仪对具有几何中心的球型标靶进行扫描获得试验数据,并利用Geomagic Studio软件对点云数据进行拟合精度评定。试验表明:Focus3D三维激光扫描仪的空间距离测量精度为0.61 mm(≤2 mm),在5~40 m范围内的径向测距精度为-2~2 mm,测距超过50 m后,测量精度呈离散趋势。

Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China

The Dunhuang–Golmud railway passes through different deserts in arid areas,especially drifting-sand desert and sandy-gravel Gobi.The near-surface wind environment and wind-sand transport process vary due to different external factors,such as topography,vegetation,and regional climate,resulting in evident spatial differences in surface erosion and deposition.Consequently,the measures for preventing wind-sand hazards will differ.However,the mechanism and control theory of sand damage remain poorly understood.In this study,we used meteorological observation,three-dimensional(3D)laser scanning,and grain-size analysis to compare and evaluate the spatial distribution of wind conditions,sand erosion and deposition patterns,and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang–Golmud railway in China.Results show that the annual mean wind speed,the frequency of sand-driving wind,and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert,indicating a greater wind strength in the sandy-gravel Gobi,which exhibits spatial heterogeneity in wind conditions.The major sediment components in sandy-gravel Gobi are very fine sand,fine sand,and medium sand,and that in drifting-sand desert are very fine sand and fine sand.We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component.The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent,with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway.The area of sand deposition in the drifting-sand desert accounts for 75.83%of the total area,with a mean deposition thickness of 0.032 m;while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31%of the total area,with a mean deposition thickness of 0.028 m,indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components.However,the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert.The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway.The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control.

三维激光扫描测量外鼻形态的可靠性研究

目的 :验证三维激光扫描测量系统测量外鼻形态的技术可靠性。方法 :取 11个石膏鼻模型为研究对象 ,通过三维激光扫描测量系统获取外鼻的三维数字化模型 ,利用相关测量软件对其进行形态测量 ,并以手工测量得到的测量结果为对照组进行统计学分析。结果 :激光三维扫描测量结果与手工测量结果高度相关。结论 :三维激光扫描测量系统进行鼻形态测量结果完全可靠 ,测量误差符合人体测量学的要求。

三维激光扫描数据获取高分辨率DTM试验研究

三维激光扫描技术能够提供实体表面点云数据,可用于获取高精度高分辨率数字地形模型。本文以重庆万州区付家岩滑坡体为例探讨了采用三维激光扫描监测技术获取数字地形模型的方法,着重讨论了相关点云数据处理流程和关键技术问题。通过结合差分GPS技术进行激光数据的相对定位和绝对定位、去噪、拼接等方法,获得了该区域地表高精度地形数据,并生成了相应的数字高程模型。试验结果初步说明该技术可用于获取小尺度高精度高分辨率数字地形模型,具有一定的应用前景。

标准牙冠三维模型的建立及其可操作平台的研究

目的 建立标准牙冠的计算机三维模型以及开发其可操作的软件平台。方法 利用三维激光扫描仪扫描全牙列 2 8颗标准牙冠的石膏模型 ,编写程序对获得的数据进行处理 ,重建各牙冠的三维图形 ,并结合国人牙冠的平均测量数据对其进行调整 ,同时在牙冠表面定义特征区和特征点 ,利用程序对牙冠进行各种变换和调整。结果 扫描仪获取了牙冠数据 ,系统重建了各牙冠的标准三维图形 ,可对牙冠进行各种变换使其产生位移、旋转和整体形变 ,按照各牙冠的解剖特点及正中牙合时的咬合接触定义了特征区 ,特征区可以在空间三个方向上产生指定形变。结论 标准牙冠的三维计算机模型精确可靠 ,其操作平台实现了多种功能 ,为进一步开发打下了基础。

三维激光扫描技术在船体外形测量中的试验性研究

介绍了三维激光扫描技术的测量原理,进行了21 m长船体外形测量的试验性研究,证明了其在快速、高效获取船体三维数据、提取船体型线方面有着较大的优越性。

长距离输水隧洞缺陷检测新技术

本文介绍了长距离输水隧洞缺陷检测的特点和重要性,分析了人工普查法的弊病,提出采用高分辨率红外热成像仪检测渗漏缺陷、高精度三维激光扫描仪检测表观缺陷的方法替代传统的人工普查法,辅以测距仪定位、数字地质雷达检测内部缺陷,并在深圳龙茜供水工程输水隧洞进行了现场试验。该技术缩短了检测占用现场的时间,具有检测速度快、数据采样率高、数字化的特点,为长距离输水隧洞缺陷检测提供了全新的方法。

变电站三维建模方法现状及展望

分析了VRML建模法、几何造型建模法、地面激光雷达建模法建立变电站模型的原理及特点。理论分析与实际案例表明VRML建模法需要对变电站每种电气设备编写程序建模,对作业人员要求较高,建模效率与直观性较低;几何造型建模法直接选取特征体建模,效率和直观性有所提提升,但其变电站模型的真实感较差;地面激光雷达建模法使变电站模型具备了真三维实景特性,建模效率高、精度高、直观性强,特别是采用Pointcloud与Auto CAD联合建模法对电气设备细节特性具有非常真实的表现效果,能满足智能电网建设需求,值得推广应用。

Cyra三维激光扫描点云数据在AutoCAD中的处理方法研究

文章详细介绍了Cyra三维激光扫描点云数据在AutoCAD中的处理过程,重点介绍了坐标纠正和进行三维建模方法,总结了AutoCAD在三维建模方面的优点,并针对一些处理中的问题提出了一些解决的方法。

船用凸轮外形轮廓线测量与建模的研究

船用凸轮进行国产化和再升级的正向设计较困难,本文基于逆向工程技术,采用激光扫描仪测量并进行逆向设计。首先对实体零件采用激光扫描仪获取表面点云数据,利用逆向软件对测量数据进行点云合并、点云去噪、点云精简、建立坐标系、点云平面投影等处理,提出分层提取边界算法。将提取的边界点云由点到线到面的流程,构造三维实体模型。实践表明,该逆向设计能快速建立实体模型,基本可以满足凸轮运动要求,有一定实践指导意义。

车载激光扫描系统及其在城市测量中的应用

激光扫描仪在测量中的广泛应用使得车载扫描系统的研究成为热点,本文首先介绍了车载激光扫描技术的原理和特点,然后详述了其在城市测量中的应用,最后指出当前应用中存在的问题及需要解决的关键技术。

三维激光扫描技术在城市建筑竣工测量中的应用研究

在分析三维激光扫描技术特点基础上,以广州市会展中心某异形建筑为工程实例,提出了一种基于三维激光扫描技术的城市建筑竣工测量方法。首先对工程概况及其作业流程进行了阐述,继而分别对三维竣工测量数据采集和处理过程中的关键技术进行了详细介绍,最后对工程结果进行了分析。研究和分析结果表明,三维激光扫描技术在结构复杂、超大规模建筑物测量中具有较好的应用前景。