Application of 3D Digital Modeling Technology in the Construction of Digital Cities

The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which was to build a digital and virtualized city that matched the real physical world, to achieve a one-to-one correspondence between all elements of the physical world and the digital virtual world. And one of its basic geographic information data was a highly similar, virtual simulation of the 3D real scene. After exploring the traditional manual 3DsMax modeling, UAV low-altitude digital oblique photogrammetry modeling, airborne laser scanning modeling and other single modeling technologies, this paper discussed the 3D digital modeling technology used by the UAV airborne laser scanning point cloud and low-altitude digital oblique photogrammetry for complementary integration, constructing the 3D scene of the digital city. This paper expounded the technical route and production process of 3D digital modeling, in order to provide technical references for related projects.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

Optimization of the forearm angle for arm wrestling using multi-camera stereo digital image correlation: A preliminary study

This study analyzes the function of different muscles during arm wrestling and proposes a method to analyze the optimal forearm angle for professional arm wrestlers.We built a professional arm-wrestling platform to measure the shape and deformation of the skin at the biceps brachii of a volunteer in vivo during arm wrestling.We observed the banding phenomenon of arm skin strain during muscle contraction and developed a model to evaluate the moment provided by the biceps brachii.According to this model,the strain field of the area of interest on the skin was measured,and the forearm angles most favorable and unfavorable to the work of the biceps brachii were analyzed.This study demonstrates the considerable potential of applying DIC and its extension method to the in vivo measurement of human skin and facilitates the use of the in vivo measurement of skin deformation in various sports in the future.

A TECHNIQUE OF DIGITAL SURFACE MODEL GENERATION

It is usually a time-consuming process to real-time set up 3D digital surface model(DSM) of an object with complex surface.On the basis of the architectural survey project of"Chilin Nunnery Reconstruction",this paper investigates an easy and feasible way,that is,on project site,applying digital close range photogrammetry and CAD technique to establish the DSM for simulating ancient architectures with complex surface.The method has been proved very effective in practice.

Using UAVs for detection of trees from digital surface models

A difficult problem in forestry is tree inventory.In this study, a GoProHero attached to a small unmanned aerial vehicle was used to capture images of a small area covered by pinus pinea trees. Then, a digital surface model was generated with image matching. The elevation model representing the terrain surface, a ‘digital terrain model’,was extracted from the digital surface model using morphological filtering. Individual trees were extracted by analyzing elevation flow on the digital elevation model because the elevation reached the highest value on the tree peaks compared to the neighborhood elevation pixels. The quality of the results was assessed by comparison with reference data for correctness of the estimated number of trees. The tree heights were calculated and evaluated with ground truth dataset. The results showed 80% correctness and 90% completeness.

Digital 3D Modeling of Whole Garment Based on Structure Illumination

With the coming of information age and the development of computer science, digitalization of whole garment is becoming more and more important. The surface of whole garment is sequent and glossy so that it is lack of the texture characteristic which is the key of digital 3D modeling. According to this reason, the structure illumination is steered into a method of this paper. The paper proposes the method by which 3D model of whole garment is created from 2D image sequences directly but not by the common techniques using general CAD model. In the paper the structure illumination is generated by the slide projector and the modeling of whole garment is based on the strict theory of the digital photogrammetry, computer vision and image processing pattern recognition. Because whole garment is lack of the applicable texture for matching, the characteristic texture generated by the structure illumination is added onto the surface of whole garment. After the characteristic texture is extracted from images and is matched well, 3D coordinates of the characteristic texture can be calculated out by the space forward intersection. Then the whole garment model is acquired by connecting all neighbour space points in the TIN and rendering the real texture of whole garment automatically. The 3D modeling method is untouched so that it is nondestructive which is just suitable for the messaline and the clothing. The method of whole garment 3D modeling proposed in the paper is flexible, effective and practical, which is confirmed by the results of the reconstructing experiments.

Positioning of Screw Holes Group Based on Digital Camera and Digital Control Drilling

Positioning of screw holes is an important production procedure for steel construction connecting with bolts. In this paper, a new production method is presented, in which the digital camera is used for taking pictures of screw holes and other techniques are advanced. This paper also indicates that the pixels of CCD chip in photogrammetry should be chosen as all geometric units in an image, such as interior elements and all kinds of distortions. The measure can also simplify the camera calibration for determining the size of non-square pixel.

大众众包技术在文物古迹数字化保护中的应用探讨

大数据分析表明,文物古迹数字化模型的在线传播和消费对文化遗产传承的影响显著,且趋势愈加明显。随着网络普及率的提高,数字化文化遗产在促进大众文化参与、丰富文化传承方式等方面发挥了积极作用。数字化模型的三维重建是一种非常普遍的文化遗产保护和存储方法,通过摄影测量技术,准确复制文化遗产对象的形态与色彩,进而实现其高质量的数字化重建。这种重建三维模型不需要设计师建模,考虑到摄影测量流程中的图像采集环节可以利用公众参与的力量,该文探讨了将大众众包技术应用于数字化文化遗产保护,建立众包共享平台的可行性,并提出了一种基于众包的图像采集方法,进一步阐明了大众众包技术在数字遗产领域的潜力。

侗族鼓楼数字化保护研究

侗族鼓楼是国家级非物质文化遗产之一,其建筑技术和建筑文化的传承和发展非常重要。本文通过分析侗族鼓楼的传承现状,利用无人机贴近摄影测量技术对鼓楼建筑进行测绘,完成三维精细化模型建模,形成数字化技术储存鼓楼建筑的信息数据以及各类型的成果文档,为侗族鼓楼建筑的保护、修复和传承提供新的思路。

无序无人机影像的并行化SfM三维重建方法

增量式运动恢复结构(ISfM)已成为无人机影像三维重建的关键技术。然而,大数据量、大重叠度和高分辨率的无序无人机影像导致的匹配对检索代价大、迭代优化误差累积和效率低的问题,使其难以满足大场景ISfM处理需求。本文提出联合全局描述子和图索引的无人机影像并行化SfM方法。针对影像特征数量大、影像检索编码本尺寸增加导致的匹配对检索效率低的问题,设计了联合全局描述子和图索引的高效影像检索方法,从而加速影像匹配。针对分块并行化SfM子场景合并存在同名点搜索效率低、内存消耗大、合并解算精度低的问题,设计了基于按需匹配图和双向重投影误差的子场景合并方法,实现无人机影像的并行化SfM重建。利用不同场景、不同采集方式获取的真实无人机影像进行试验,结果表明本文方法能够实现36~108倍加速比的匹配对检索,ISfM重建效率达到30倍加速,且相对定向和绝对定向精度与传统方法相当。

基于多源数据融合的数字工厂三维模型重建与可视化

如何为企业安全生产、应急救援指挥、事故灾害调查等提供现势、详尽、精确的空间基础地理信息数据以辅助智能决策,是政府与企业面临的重要难题。本文从虚拟构建数字工厂关键技术出发,通过融合机载倾斜摄影测量技术宏观建模与局部地面三维激光扫描技术精细建模,构建厂区模型;以前端Cesium框架和Web GL技术为依托,结合微软开发的Web预览版Bing地图服务,实现用户浏览器端的“数字工厂”三维场景可视化浏览,提升企业安全生产信息化水平与防范并遏制重大安全事故。

多时相数字孪生滑坡变形监测方法与应用研究--以金沙江白格滑坡为例

高位隐蔽滑坡因为难到达、难识别、难监测,致使成灾表现具有极强的突发性和破坏性。针对传统人工地面调查和地面布设监测设备存在危险系数高、工作效率低、设备易损坏和离线误报率高等问题,提出基于无人机倾斜摄影测量技术构建高位隐蔽滑坡数字孪生体的方法,通过信息化、数字化手段对地质灾害变形特征及时空演化规律进行监测分析。以西藏金沙江白格滑坡为研究对象,利用无人机倾斜摄影测量技术获取2019年4月—2021年9月共计10期次航测数据,融合多源数据构建了多时相数字孪生滑坡体,通过多期孪生滑坡体实现对白格滑坡整体滑移、局部微变形、滑塌体积等多维要素的高精度定量分析,并及时应用于白格滑坡时空演化分析和监测预警中。研究表明:白格滑坡在2019—2021年监测期内存在持续变形迹象,强变形主要位于滑坡两侧及后缘,渐有扩大趋势,存在垮塌堵江风险。运用多时相数字孪生滑坡变形监测手段实现对地质灾害定性-定量化特征描述与风险评估,具有快速灵活、覆盖全面、不受复杂艰险地形条件限制等优势,可为高位隐蔽滑坡等斜坡灾害大梯度形变监测提供工程实践参考。

一种GNSS与相机集成的实时水边界测绘新方法

针对水边界测绘现有方法施测困难等问题,提出一种免像控、免惯导支持的实时水边界船基摄影测量方法。该方法通过GNSS罗经、数码相机、计算机组网与通信端口编程,实现数据的全自动采集;采用自检校光束法实现传感器的标定与数据配准;构建自由网光束法空三平差模型,引入水位和外方位线元素最小范数条件约束,实现三维水边线的高精度提取。长江实时水边界测绘典型实验结果表明,本文方法切实可行、精度可靠,中误差优于0.2m,可有效消除作业人员安全风险,降低劳动强度,实现水下地形与水边界一体化测绘,且具有成本低、续航持久等显著优势。

基于无人机数字近景摄影测量的服役边坡监测方法

针对现有边坡变形监测技术自动化与智能化程度低及安设复杂且对边坡有损坏等问题,提出一种基于无人机数字近景摄影测量的服役边坡坡表变形监测方法。根据数字近景摄影测量的相关理论,确定了数码相机内参数标定和监测点坐标解算方法,研制出一种可布设在服役边坡坡表的数字近景摄影测量和全站仪测量通用的变形监测目标物,实现对边坡的联合监测。研究结果表明,数字近景摄影测量技术配合专门设计的变形监测目标物对边坡坡表变形较为敏感,第一期和第二期的监测点位中误差分别为3.3 mm和1.7 mm,水平位移监测的点位和垂直位移监测的高程中误差分别为3.5 mm和1.6 mm,达到毫米级的监测精度,满足滑坡监测标准的精度要求;同时变形监测目标物制作可靠、成本低廉,具有较高的应用价值。

基于异构无人机协同的路桥设施数字化管理系统

路桥设施信息化管理存在工作量大、工作时间长、条件艰苦、成本高和效率低等问题。基于路桥设施数字化管理迫切需求,综合应用无人机航拍巡检、影像快速拼接、倾斜摄影测量、WebGIS以及BIM技术,设计路桥设施数字化管理系统,开展路桥设施数字化管理建设,实现无人机影像快速拼接成图支撑应急应用。基于航拍影像的路桥病害检测精细化应用、多机航拍的路桥精细化模型构建,以及基于路桥设施数字化管理Web平台建设,共同推进路桥设施管理信息化、数字化、可视化水平,提高管理效率。

极端复杂地貌下的自适应贴近摄影测量研究——以张家界天门山实景数字孪生建模为例

实景数字孪生集实景三维、数字孪生、摄影测量、云计算等新型技术于一体,是一种将真实地物或空间1∶1复刻到虚拟空间、反映其全生命周期过程的数字化技术,针对现有摄影测量技术不能较好的对复杂地貌进行自动化高精度数字孪生建模的问题,提出了一种针对张家界地貌的智能航迹规划方法,并将其成功应用于实景三维张家界项目中,实现在极端复杂环境下的快速高精模型构建。结果表明,该方法在作业安全性、采集效率、成果质量上较传统摄影测量方法提升显著,所构建的三维模型相对精度达到厘米级甚至毫米级,高精度复刻了张家界立体地貌,可为国土空间规划、景区智能化管理、大众出行导航、地质灾害防治、林业普查、生态修复等工作提供更加科学精准的三维数字空间分析基础。

13.2 m天线日照温度变形主面精度测量研究

13.2 m反射面天线有口径大、面形精度要求高的特点,并长期经受四季、昼夜温差带来的主反射面形变。针对主反射面承受夏季高温日晒,产生的结构变形,提出了一种主面精度日照变形测量分析方法,利用工业数字摄影测量技术,对主反射面精度进行测量。结果表明,主面最佳拟合精度受温度影响较小,固定坐标系拟合精度受温度影响较大。由于重力变形和高温影响,在俯仰70°工况时,12时和14时主面最佳拟合精度超出了0.3 mm指标,相关试验结果可为同类大口径反射面天线主面精度日照温度变形分析提供参考依据。

ICam4D摄影测量技术应用于全牙弓种植固定终修复的临床研究

目的:探讨ICam4D摄影测量技术在全牙弓种植固定修复终印模制取中的临床效果。方法:选取需进行终修复的全牙弓种植固定修复患者30名。对照组及实验组各15名,分别采用传统夹板印模技术制取硅橡胶开窗印模及ICam4D摄影测量技术获取数字化印模完成最终固定义齿修复。患者填写印模制取舒适度及修复体满意度视觉模拟量表(Visual Analogue Scale,VAS),比较两组制取印模耗时、患者舒适度、修复体就位及边缘适合性、修复体满意度及修复后随访差异,评估ICam4D摄影测量技术在全牙弓种植固定修复中的临床效果。结果:全部终修复体均精准被动就位,边缘适合性均为I级;印模制取耗时对比,实验组(15.67±2.77)min显著少于对照组(51.47±5.88)min,差异有统计学意义(P<0.05);印模舒适度(VAS)评分对比,实验组(94.60±13.64)显著高于对照组(55.13±13.64),差异有统计学意义(P<0.01);两组修复体咀嚼、美观、发音满意度(VAS)评分均无显著性差异(P>0.05);两组随访,螺丝松动及折裂率、支架折裂率均为0%,种植体成功率均为100%。结论:ICam4D摄影测量技术应用于全牙弓种植固定修复终印模制取,节约椅旁操作时间,提高患者舒适度,准确性能满足临床需求,具有较好的临床预后。