基于三维声呐点云的河口水闸水下结构安全评估

河口水闸水下结构安全对于水闸工程、整个河道,以及周边居民地的安全具有重要意义。在低可视度的水体环境中,采用传统人工潜水探摸方式进行水下结构安全检测效率低下。为提高效率,三维扫描声呐逐步应用于相关水下结构的安全检测中。本文以BlueView BV5000型三维扫描声呐系统在苏州河河口水闸水下结构的实测数据为基础,经滤波、测站拼接等处理过程,利用所得三维声呐点云对该水闸的水下结构进行安全评估。采用人工探摸方式对评估结果进行验证,结果表明,三维扫描声呐在水下结构安全评估中具有优越性,可为后续运维保障提供数据基础。     

FJCORS 与测深仪组合系统在水下地形测量中的质检探讨

根据连续运行卫星定位服务系统可实时获取三维坐标、测深仪可实时获取水深数据的特点,提出水下地形测量中快速获取水下地形点高程和水深的方法。 FJCORS和测深仪组合系统不但广泛应用于水下地形测量,而且还可对其成果质量进行检查和分析,确保成果数据的可靠性,保证水下地形测量成果合格。     

水上水下一体化三维河道场景构建与展示

随着无人机与新型航拍技术的发展,无人机倾斜摄影技术在大范围地形数据采集过程中发挥了重要作用,三维测绘相关研究得到了极大的促进。而针对水利行业所需的水上地形与水下地形一体化生产过程的研究相对较少。本文布设统一控制点,采用固定翼无人机倾斜摄影测量技术进行水上地形测绘,应用RTK配合测深仪在船上进行水下河道三维地形数据采集,对于涉河建筑物采用BIM软件进行参数化建模。最后,针对水上地形数据,水下河道地形数据及建筑物三维模型进行融合处理,得到水上水下一体化三维河道场景,搭建Cesium平台进行三维展示。其研究成果可为水上水下一体化测绘与可视化提供技术帮助,有助于推进智慧水利的应用发展。     

Exploring differences of visual attention in pedestrian navigation when using 2D maps and 3D geo-browsers

ABSTRACT

Despite the now-ubiquitous two-dimensional (2D) electronic maps, three-dimensional (3D) globe viewers, or 3D geo-browsers such as Google Earth and NASA World Wind have gained much attention. However, the effect of such interactive 3D geo-browsers on spatial knowledge acquisition and decision-making is not well known. This study aims to explore the potential benefits of using interactive 3D geo-browsers in three processes of pedestrian navigation (self-localization, spatial knowledge acquisition, and decision-making) in digital environments. We employed eye tracking to show differences of visual attention in pedestrian navigation between a 2D map (Google Map) and a 3D geo-browser (Google Earth). The results indicated that benefits and drawbacks of 3D representations are task dependent. Participants using the 3D geo-browser had an extensively visual search resulting in significantly longer response time than the 2D participants for spatial knowledge acquisition, whereas 3D users performed a more efficient visual search and resulted in a better navigation performance at complex decision points. We speculate that the inefficient knowledge acquisition when using the 3D geo-browser was most probably due to information overload and obstructed views. Landmarks in photorealistic 3D models assisted recall of spatial knowledge from mental maps, which contributed to efficient decision-making at a complex turning point. These empirical results can be helpful to improve the usability of pedestrian navigation systems.     

Use of laser range and height texture cues for building identification

Airborne LiDAR has found application in an increasing number of mapping and Geo-data acquisition tasks. Apart from terrain information generation, applications such as automatic detection and modeling of objects like buildings or vegetation for the generation of 3-D city models have been explored. Besides the height itself, height texture defined by local variations of the height is a significant parameter for object recognition. The paper explores the potential of the analysis of height texture as a cue for the automatic detection of objects in LiDAR datasets. A number of texture measures were computed. Based on their definition and computation these measures were used as bands in a classification algorithm, and objects like buildings, single trees, and roads could be recognized.     

Investigating Effects of Seafloor Topography on Sea Surface Currents in the Caspian Sea and Northern Indian Ocean

Seafloor topography certainly has an impact on ocean circulation in different ways. Due to this assumption, the sea surface currents calculated by optical flow (Horn–Schunck) and geostrophic currents methods are analyzed to observe this impact. Pair of sea surface temperature imageries, calculated sea surface height and sea level anomaly are showed beside depth map in areas with meaningful bathymetric features such as underwater mountains and pools. The reason for the formation of some eddies in the Caspian Sea and Indian Ocean is concluded from the location of pools and knolls. In this study, in addition to introducing new time span for calculating geostrophic currents, Ocean Surface Current Analyses Real-Time (OSCAR) currents are applied to validate our estimated currents. Variety of products such as sea surface temperature imageries, OSCAR currents, depth map, calculated results like sea level anomaly and absolute dynamic topography and estimated currents via optical flow and geostrophic currents have been collected in this paper to make very detailed investigation on depth effect on mentioned water parameters. Results show that impacts of knolls and pools are meaningfully clear in optical flow and geostrophic currents in shaping and rationing water motions.     

REMOTE SENSING IN THE STATISTICAL CHARACTERIZATION OF ATMOSPHERIC PARAMETERS

An analysis of the statistical characteristics of the optical depth of suspended particulates was made in several parts of the visible spectrum as it is affected by meteorological conditions. The paper tests whether the association of the statistical characteristics of the spectral structure of visible radiation with meteorological parameters is strong enough to serve as part of the explanation for the onset of different states of atmospheric turbidity. Equations are derived that permit estimation of atmospheric optical conditions from meteorological data.     

无人机遥感在大型不可移动文物三维重建中的应用

针对大型不可移动文物三维重建技术存在的困难,本文基于无人机遥感等平台,利用基于图片的三维重建技术,设计了一种低成本、简便高效、较高精度的大型不可移动文物的表面精细几何纹理获取与三维重建的技术流程,对建模中的技术问题进行了研究,并对其精度和实用性进行了评价。其结果较好地满足了文物测量的精度要求;为文物保护与展示等研究提供了新的思路,能全方位、近距离面向公众做三维展示;结果带有精确的地理位置信息,可作为三维GIS平台新的数据采集方法和数据源。     

Relevance of airborne lidar and multispectral image data for urban scene classification using Random Forests

Airborne lidar systems have become a source for the acquisition of elevation data. They provide georeferenced, irregularly distributed 3D point clouds of high altimetric accuracy. Moreover, these systems can provide for a single laser pulse, multiple returns or echoes, which correspond to different illuminated objects. In addition to multi-echo laser scanners, full-waveform systems are able to record 1D signals representing a train of echoes caused by reflections at different targets. These systems provide more information about the structure and the physical characteristics of the targets. Many approaches have been developed, for urban mapping, based on aerial lidar solely or combined with multispectral image data. However, they have not assessed the importance of input features. In this paper, we focus on a multi-source framework using aerial lidar (multi-echo and full waveform) and aerial multispectral image data. We aim to study the feature relevance for dense urban scenes. The Random Forests algorithm is chosen as a classifier: it runs efficiently on large datasets, and provides measures of feature importance for each class. The margin theory is used as a confidence measure of the classifier, and to confirm the relevance of input features for urban classification. The quantitative results confirm the importance of the joint use of optical multispectral and lidar data. Moreover, the relevance of full-waveform lidar features is demonstrated for building and vegetation area discrimination.     

GZCORS在广州轨道交通水下地形测量中的应用

水下地形图是轨道交通工程规划、设计、施工的重要基础资料,本文以广州轨道交通三号线流溪河水下地形测量为例,阐述了广州市连续运行参考站城市3维定位系统(GZCORS)在水下地形测量中的作业模式、方法及精度。该种作业模式在河道、沿海港口等水下地形测量中有着广阔的应用前景。     

Data model and visualization of 3D city landscape based on integrated databases

Data acquisition and modeling are the two important, difficult and costful aspects in a Cybercity project. 2D-GIS is mature and can manage a lot of spatial data. Thus 3D-GIS should make the best of data and technology of 2D-GIS. Construction of a useful synthetic environment requires integration of multiple types of information like DEM, texture images and 3D representation of objects such as buildings. In this paper, the method for 3D city landscape data model and visualization based on integrated databases is presented. Since the data volume of raster are very huge, special strategies(for example, pyramid gridded method) must be adopted in order to manage raster data efficiently. Three different methods of data acquisition, the proper data structure and a simple modeling method are presented as well. At last, a pilot project of Shanghai Cybercity is illustrated.     

Data model and visualization of 3D city landscape based on integrated databases

Data acquisition and modeling are the two important, difficult and costful aspects in a Cybercity project. 2D-GIS is mature and can manage a lot of spatial data. Thus 3D-GIS should make the best of data and technology of 2D-GIS. Construction of a useful synthetic environment requires integration of multiple types of information like DEM, texture images and 3D representation of objects such as buildings. In this paper, the method for 3D city landscape data model and visualization based on integrated databases is presented. Since, the data volume of raster are very huge, special strategies (for example, pyramid gridded method) must be adopted in order to manage raster data efficiently. Three different methods of data acquisition, the proper data structure and a simple modeling method are presented as well. At last, a pilot project of Shanghai Cybercity is illustrated.     

高分辨率光学卫星影像全球重点区域三维建模方法——以迪拜市为例

针对境外典型区域精细化三维建模数据获取与产品制作技术难点,本文设计归纳出一种高分辨率光学卫星影像精细化三维建模方法。选取迪拜市中心城区为试验区域,以WorldView-3、GeoEye-1等主流高分卫星影像为主要数据源,以互联网众源影像为辅助数据源,利用卫星影像精准定向精化的RPC参数及生成的精准几何信息（DSM/DOM）,完成区域内主要建筑物的三维模型生产制作,并形成高分辨率卫星影像三维建模原型系统,满足全球地理信息资源建设与维护更新工程,快速制作符合精度和精细度要求的三维数字模型的需要。     

海洋测量技术在输水隧洞进水口检测中的应用

本文以某输水隧洞进水口岩塞爆破后水下检测为例,综合利用多波束声呐、水下机器人、彩色图像声呐等声学和光学相结合的海洋测量技术,获得高精度、全覆盖、高时效性的输水隧洞进水口测量数据。检测结果显示：多波束声呐水下地形测量地形分辨率达1.25 cm,实现输水隧洞进水口岩塞爆破后的形状、尺寸、平面位置、高程及洞口周围边坡高精度检测;水下机器人深入隐蔽复杂的隧洞水底环境,搭载的彩色图像声呐剖面扇扫可拟合隧洞进水口岩塞段、锁口段和集渣坑断面,高清水下摄像呈现了爆破后洞身衬砌质量和集渣坑内块石堆积状况。本文综合利用海洋测量技术,实现了复杂环境水下隧洞的安全、高效、全覆盖检测,其技术手段可为相关水下工程测量提供借鉴。     

利用GIS技术对莲花电站水库库容曲线复核分析

通过以GPS载波相位差分定位技术和回声测深仪等组成的三维数据自动采集系统,按照规定的测线,快速准确地采集高密度、高精度水下地形数据,获取水底测点平面和深度信息,利用以ArcGIS为平台的数据处理编辑软件,制作水下地形图、计算库容、生成库容曲线,并与初设库容曲线进行复核分析,为探查泥沙淤积对库容的影响、节能增效提供详实可靠的基础数据。     

Automatic reasoning for geometric constraints in 3D city models with uncertain observations

This paper presents a novel approach to automated geometric reasoning for 3D building models. Geometric constraints like orthogonality or parallelity play a prominent role in man-made objects such as buildings. Thus, constraint based modelling, that specifies buildings by their individual components and the constraints between them, is a common approach in 3D city models. Since prototyped building models allow one to incorporate a priori knowledge they support the 3D reconstruction of buildings from point clouds and allow the construction of virtual cities. However, high level building models have a high degree of complexity and consequently are not easily manageable. Interactive tools are needed which facilitate the development of consistent models that, for instance, do not entail internal logical contradictions. Furthermore, there is often an interest in a compact, redundancy-free representation. We propose an approach that uses algebraic methods to prove that a constraint is deducible from a set of premises. While automated reasoning in 2D models is practical, a substantial increase in complexity can be observed in the transition to the three-dimensional space. Apart from that, algebraic theorem provers are restricted to crisp constraints so far. Thus, they are unable to handle quality issues, which are, however, an important aspect of GIS data and models. In this article we present an approach to automatic 3D reasoning which explicitly addresses uncertainty. Hereby, our aim is to support the interactive modelling of 3D city models and the automatic reconstruction of buildings. Geometric constraints are represented by multivariate polynomials whereas algebraic reasoning is based on Wu’s method of pseudodivision and characteristic sets. The reasoning process is further supported by logical inference rules. In order to cope with uncertainty and to address quality issues the reasoner integrates uncertain projective geometry and statistical hypothesis tests. Consequently, it allows one to derive uncertain conclusions from uncertain premises. The quality of such conclusions is quantified in a way which is sound both from a logical and a statistical perspective.     

3D GIS技术研究发展综述

回顾了3DGIS的发展进程,从三维空间数据获取,三维数据模型,三维空间数据管理和分析以及三维可视化技术4个方面综述了3DGIS技术的发展。探讨了目前研究3DGIS的4个热点问题:①数据源集成快速获取数据的方法;②不同数据模型的集成;③支持空间分析的面向对象的数据模型;④城市三维模型。     

基于倾斜影像的城市场景隐式曲面重建

在基于倾斜影像的城市场景重建过程中,由于获取影像时存在场景遮蔽和大视点变化的情况,建筑物立面等区域存在着影像密集匹配点云稀疏甚至空洞的情况,自动化重建难度大,难以反映建筑物的真实形态。本文提出了一种新的基于倾斜影像的城市场景隐式曲面重建方法：首先,以倾斜影像密集匹配点云为基础建立Delaunay四面体;然后,对Delaunay四面体进行约束图割,提取出可视化的三角面,进而更加精确地估计点云的法向信息;最终,结合Screened Poisson曲面重建,实现了城市场景的隐式曲面重建。通过多种隐式曲面重建方法的对比试验,验证了本方法的准确性和适用性。     

依托航空模拟平台的激光雷达技术课程实践教学装备

为了能更好地理解激光雷达技术工作原理与三维信息采集全过程,规避现有激光雷达技术,尤其是机载激光雷达,在实践教学中受场地限制的不利条件,本文依托于中国矿业大学(北京)沙河校区的航空模拟平台,自主研发了一套基于单线激光雷达与行程测距仪集成的三维激光扫描装备,阐述了该装备集成的数学原理,设计了三维数据采集实践教学方法,并进行了三维数据采集的实践体验与数据质量评价。结果表明,该装备采集三维点云的精度优于99%,可为激光雷达技术的实践教学、创新训练及本科毕业设计等环节提供有效的硬件支撑,并可在仓储方量核算等工程应用方面进行推广。     

基于实景三维的地形图编绘软件研发与使用技术流程的研究

近年来随着无人机航摄技术和实景三维建模技术逐渐成熟,人们逐渐探索使用实景三维模型进行1∶500地形图采集编绘。这种编绘与传统的立体像对测图不同,是一种直观的基于模型的采集。它与立体测图相比各有优缺点,精度控制相对较弱,但因其属于基于摄影测量成果的采集,因此可一次建模,多次使用。本文讨论了实景三维模型地形图编绘软件的研发技术流程,并且针对具体案例,对该软件编绘的效率和精度进行了分析。