摘要

为了满足复杂景区环境中游客的个性化导航需求，建立了一种综合考虑景区地形、气象与游客密度等多维动态环境要素的导航网格模型，在此基础上设计实现了智慧旅游动态寻径的A*算法.融合多维动态环境信息的景区综合导航网格模型突破了传统旅游地图主要依赖静态路网模型的局限，支持实时环境感知并适应游客偏好的动态路径规划.以都江堰景区为例进行了实验验证，实验结果表明，本文算法的最优路径规划结果比景区推荐路径的综合距离缩短了17.6%，同时有助于为游客提供动态、智能化、精准化和一体化的智慧旅游位置信息服务.

摘要

半全局匹配实质是在视差连续性假设下的离散优化方法。为克服视差断裂带影响，依赖一组参数控制视差不一致性。 若参数过小，在平面内难以保证视差连续性，产生明显噪声，导致凹凸不平现象；若参数过大，将致使物体表面过于平滑，难以保留视差断裂等重要特征。为克服上述问题，本文提出了一种顾及纹理特征的自适应密集匹配方法：首先，检测影像纹理特征并定量表达纹理丰富性程度；其次，依据纹理丰富程度与视差差异存在正相关的规则知识，实现匹配参数依据纹理信息的自适应选择；最后，采用上述参数进行自适应的半全局匹配。通过ISPRS基准数据集和国产SWDC-5获取的倾斜影像进行试验分析证明，本文方法能够有效减少低纹理区域匹配噪声，同时更有效保留边缘特征。

摘要

为了避免灾情误判和误报，准确探测和剔除滑坡形变监测数据中的粗差已经成为提高监测数据质量亟待解决的问题。 已有方法主要针对单一传感器数据独立处理，且过度依赖数据变化本身的突变-平滑关系，难以有效区分粗差和外界因素突变引起的奇异值。介绍了一种知识引导的滑坡监测数据粗差剔除方法，通过粗糙集属性约简筛选具有相关关系的多源滑坡观测数据，并结合多元统计理论挖掘粗差影响因素间的时空约束关系，利用不同类型滑坡监测数据变化间的相关性规律，将多因素影响下的滑坡形变抽象为多模式的组合根据不同模式自适应选择多因子模型以此引导卡尔曼滤波模型更新，从而实现滑坡形变监测粗差的定位与剔除。实验证明，该方法不仅能够有效甄别因环境变化引起的突变， 并且能显著提高滑坡形变监测数据粗差自适应剔除的准确性、可靠性与智能化水平。

摘要

针对大规模复杂三维城市场景三维可视化的数据调度效率不高、视觉一致性差等关键问题， 提出了一种视觉感知驱动的复杂三维城市场景数据自适应组织管理与动态调度方法. 该方法根据三维场景数据的空间分布特征，利用自适应四叉树对复杂三维城市场景进行不同层次粒度的划分， 并自底向上遍历四叉树，为中间节点生成LOD（level of detail）和计算各个层级的几何误差， 构建灵活的多粒度三维瓦片模型，最后根据屏幕误差评估建筑物模型的三维几何特征（形状、尺寸、高度）等视觉感知参数，约束不同细节层次模型的自适应调度. 选择了柏林4个细节层次的三维城市模型数据，进行交互式三维漫游测试.实验结果表明，基于视点相关HLOD（hierarchical LOD）动态调度，动态可视化的渲染帧率始终保持在40 f/s左右， 达到了网络环境下复杂三维城市场景数据动态调度的高效性和三维可视化视觉一致性的要求.

摘要

应急测绘中的无人机调度存在时空环境约束复杂、调度方案多样的特点， 现有调度主要以人为经验判断为主，方案粗放不可靠，难以综合考虑应急过程中复杂多变的因素， 结果的精准性与可靠性较低。为实现灾后应急测绘的快速响应，提出了一种无人机资源的快速调度方法， 综合考虑应急测绘任务需求、优先级、时间窗、作业区域地理环境和无人机测绘资源能力等约束条件， 构建了以任务成果收益效率最大化、任务完成率最大化以及调度风险最小化等为多优化目标的应急测绘无人机资源调度模型，并运用蚁群算法实现对模型的求解。 实验结果验证了调度方法的有效性。

摘要

时空大数据可视分析是近年国际大数据分析与数据可视化领域研究的热点前沿， 也是全空间信息系统的核心研究内容之一。本文针对时空大数据多源、多粒度、多模态和时空复杂关联的特点， 按照描述性、解释性和探索性3个层次分类归纳了现有时空大数据可视分析方法， 论述了时空大数据可视分析中多模态特征筛选、新型人机交互分析以及探索性可视推理等技术难点和主要发展动态。 研究表明，以数据可视化为主的描述性可视分析研究相对成熟，以可视环境下交互式挖掘分析实现问题诊断为主的解释性可视分析已成为当前大数据分析的焦点， 而面向复杂问题协同决策的探索性可视分析方法则是大数据分析有待突破的重要发展方向。

摘要

针对单直线匹配过程中缺乏考虑邻近直线特征之间关系，纹理断裂处单一直线描述符的弱可靠性， 提出了一种顾及拓扑关系的立体影像直线特征可靠匹配算法。该算法首先根据直线间距离、角度等基本拓扑关系对参考影像、搜索影像上提取的直线进行编组； 然后将编组得到的直线组作为匹配基元，充分利用直线特征组内的拓扑关系，依次采用核线约束、单应矩阵约束、象限约束、不规则三角形区域灰度相关约束对其进行匹配；最后将同名直线组分裂为两对同名单直线、并对分裂后的结果进行整合、拟合、检核等后处理，得到“一对一”的同名直线。选取典型纹理特征的航空影像和近景影像进行参数分析及直线匹配试验， 结果表明，本文算法能获取可靠的直线匹配结果。

摘要

卫星对侦查区域的覆盖语义是影响侦查覆盖效率的关键因素之一。 针对现有覆盖算法低效耗时的技术瓶颈，提出了一种针对成像卫星区域覆盖的自适应规划方法， 包括自适应的网格划分、平衡成像精度和覆盖效率的最大可视覆盖计算以及窗口优化的卫星区域覆盖策略。 通过与常用经典算法对比，验证了本文方法的有效性和鲁棒性。 本文方法已成功应用于某些在轨卫星的区域覆盖任务。

摘要

The semantic classification of point clouds is a fundamental part of three-dimensional urban reconstruction. For datasets with high spatial resolution but significantly more noises, a general trend is to exploit more contexture information to surmount the decrease of discrimination of features for classification. However, previous works on adoption of contexture information are either too restrictive or only in a small region and in this paper, we propose a point cloud classification method based on multi-level semantic relationships, including point–homogeneity, supervoxel–adjacency and class–knowledge constraints, which is more versatile and incrementally propagate the classification cues from individual points to the object level and formulate them as a graphical model. The point–homogeneity constraint clusters points with similar geometric and radiometric properties into regular-shaped supervoxels that correspond to the vertices in the graphical model. The supervoxel–adjacency constraint contributes to the pairwise interactions by providing explicit adjacent relationships between supervoxels. The class–knowledge constraint operates at the object level based on semantic rules, guaranteeing the classification correctness of supervoxel clusters at that level. International Society of Photogrammetry and Remote Sensing (ISPRS) benchmark tests have shown that the proposed method achieves state-of-the-art performance with an average per-area completeness and correctness of 93.88% and 95.78%, respectively. The evaluation of classification of photogrammetric point clouds and DSM generated from aerial imagery confirms the method’s reliability in several challenging urban scenes.

摘要

Intelligent navigation and facility management in complex indoor environments are issues at the forefront of geospatial information science. Indoor spaces with fine geometric and semantic descriptions provide a solid foundation for various indoor applications, but it is difficult to comprehensively extract free multi-floor indoor spaces from complex three-dimensional building models, such as those described using CityGML LoD4, with existing methods for the subdivision or extraction of indoor spaces based on vector topology processing. Therefore, this paper elaborates a new voxelbased approach for extracting free multi-floor indoor spaces from 3D building models. It transforms the complicated vector processing tasks into a simple raster process that consists of three steps: voxelization with semantic enhancement, voxel classification, and boundary extraction. Experiments illustrate that the proposed method can automatically and correctly extract free multi-floor indoor spaces, especially two typical kinds of open indoor spaces, namely, lobbies and staircases.

摘要

Indoor emergency response plays a critically important role in disaster management for cities, which must consider the evacuation of people in a dynamic indoor environment. The spatial model is the foundation for the specific analysis of indoor emergency responses, such as evacuations. The current spatial model for evacuation has three primary pitfalls: (1) it primarily focuses on static spatial information, such as rooms, doors, and windows, and lacks dynamic information, such as events and sensors; (2) it mainly focuses on the horizontal space and the static scene and lacks a multi-story component that considers the different properties of stairs compared to planar areas; and (3) it places emphasis on the indoor navigation calculation with a 2D/3D network, which lacks individual properties that can support more complicated analysis, such as congestion and stagnation. In this paper, we propose a dynamic indoor field model with three typical characteristics. (1) It includes not only static information but also dynamic information, such as outdoor and indoor building geometry, sensors, fire spread, and personnel behavior. (2) It supports multi-story buildings from the macro level (building level and floor level) to the micro level (room level and individual level) based on horizontal and vertical indoor space. (3) It supports spatial calculations based on a three-dimensional space grid and can analyze potential congestion and stagnation during evacuation. We design a corresponding evacuation method that supports individual evacuation route finding and evacuation assessment. We perform a series of analyses of the applicability of the proposed model and the efficiency of the designed evacuation method based on multi-story evacuation studies. The simulation includes a total evacuation population exceeding 7000 individuals, and the analysis suggests that the new model and algorithm are effective in planning indoor emergency routes that avoid potential congestion or stagnation.

摘要

The flood disaster management system (FDMS) is a platform developed to provide ongoing disaster reduction capabilities that cover the entire process of flood management. The ontology-based approach links environmental models with disaster-related data to support FDMS-constructed workflows with suitable models and recommend appropriate datasets as model input automatically. This automated activity for model selection and data binding reduces the time-consuming and unreliable operations involved in traditional management techniques, which rely on manual retrieval through simple metadata indices—typically when flood management personnel are overwhelmed with large quantities of observed data. The OpenMI-based modular design used in the system unifies interfaces and data exchange to provide flexible and extensible architecture. Subsequent 3D visualization improves the interpretability of disaster data and the effectiveness of decision-making processes. This paper presents an overview of the design and capabilities of FDMS that provides one-stop management for flood disasters.

摘要

Monitoring, response, mitigation and damage assessment of disasters places a wide variety of demands on the spatial and temporal resolutions of remote sensing images. Images are divided into tile pyramids by data sources or resolutions and published as independent image services for visualization. A disaster-affected area is commonly covered by multiple image layers to express hierarchical surface information, which generates a large amount of namesake tiles from different layers that overlay the same location. The traditional tile retrieval method for visualization cannot distinguish between distinct layers and traverses all image datasets for each tile query. This process produces redundant queries and invalid access that can seriously affect the visualization performance of clients, servers and network transmission. This paper proposes an on-demand retrieval method for multi-layer images and defines semantic annotations to enrich the description of each dataset. By matching visualization demands with the semantic information of datasets, this method automatically filters inappropriate layers and finds the most suitable layer for the final tile query. The design and implementation are based on a two-layer NoSQL database architecture that provides scheduling optimization and concurrent processing capability. The experimental results reflect the effectiveness and stability of the approach for multi-layer retrieval in disaster reduction visualization.

摘要

Constructing 3D railway scenes helps improve the railway information construction ability and the comprehensive railway management level. However, the existing modeling methods have disadvantages such as low flexibility in scene configuration, weak extensibility of scene objects and poor reusability of modeling knowledge. To enable multitype 3D railway scenes to be automatically constructed, a template-based knowledge reuse method was proposed in this paper. First, based on parsing of modeling operation characteristics and modeling knowledge expression, a modeling knowledge template was designed to store modeling knowledge and modeling operations in a parameterized way. The contents of this template were described in terms of semantic information, geometric information, topologic information and reference system information, and the method for instantiating the modeling knowledge template was proposed. Second, a scene configuration template was designed to organize the instantiated modeling knowledge files and scene objects. By the use of a flexible tree structure, the scene configuration template enables extensibility of scene objects. Finally, the two types of templates were parsed in terms of scene organization, linear referencing information, geometric and topologic relationships, and semantic descriptions. In this way, different types of 3D railway scenes were generated automatically. After a prototype system was developed, experiments on automatic modeling of two 3D railway scenes were carried out to verify the template-based knowledge reuse method. The experimental results show that the proposed method can be used to generate multitype 3D railway scenes automatically. With this method, model combination can be configured, model types can be extended and modeling knowledge can be reused.

摘要

A novel method called knowledge-guided spatio-temporal consistent correlation analysis (KSTCCA) was developed to discover reliable deformation features induced by multiple factors based on multimode landslide monitoring data. Compared to conventional approaches, KSTCCA integrates both temporal and spatial correlation analysis to improve the consistency of deformation patterns and capture the spatio-temporal heterogeneities in multimode monitoring data. KSTCCA considers both the landslide deformation mechanisms and the relationships between different influential factors as knowledge. Moreover, the method extracts the morphological structures of monitoring curves based on a seven-point approach and identifies knowledge rules using the k-means clustering method. Under the guidance of prior knowledge, a spatial correlation analysis is conducted based on support vector regression, and a temporal correlation analysis of the time lag is carried out based on the morphological structure features. Finally, three kinds of typical monitoring data, including deformation, rainfall, and reservoir water level data collected in the Baishuihe landslide area, China, are used for experimental analysis to verify the validity of the proposed method.

摘要

Improving the matching reliability of multi-sensor imagery is one of the most challenging issues in recent years, particularly for synthetic aperture radar (SAR) and optical images. It is difficult to deal with the noise influence, geometric distortions, and nonlinear radiometric difference between SAR and optical images. In this paper, a method for SAR and optical images matching is proposed. First, interest points that are robust to speckle noise in SAR images are detected by improving the original phase-congruency-based detector. Second, feature descriptors are constructed for all interest points by combining a new Gaussian-Gamma-shaped bi-windows-based gradient operator and the histogram of oriented gradient pattern. Third, descriptor similarity and geometrical relationship are combined to constrain the matching processing. Finally, an approach based on global and local constraints is proposed to eliminate outliers. In the experiments, SAR images including COSMO-Skymed, RADARSAT-2, TerraSAR-X and HJ-1C images, and optical images including ZY-3 and Google Earth images are used to evaluate the performance of the proposed method. The experimental results demonstrate that the proposed method provides significant improvements in the number of correct matches and matching precision compared with the state-of-the-art SIFT-like methods. Near 1 pixel registration accuracy is obtained based on the matching results of the proposed method.

摘要

受全球极端气候变化和人类活动影响,复杂滑坡灾害时空演变过程复杂,其时空演变的高突变性、高隐蔽性、高动态性,以及孕育环境的时空异质性与不确定性等十分突出,复杂地形地质条件下滑坡灾害模拟分析已经成为世界性难题.为此,本文提出动态观测数据驱动的滑坡灾害精准模拟分析方法,设计了动态数据驱动的复杂滑坡灾害精准模拟分析框架,阐释了滑坡灾害过程时空变化的显式语义描述,任务驱动的空天地一体化观测数据规划与调度,计算与存储融合的复杂滑坡灾害实时数据组织与管理,变化驱动的多源动态观测数据实时接入与自主加载,多源动态观测数据在线智能处理,复杂滑坡灾害模拟模型参数智能率定等关键技术,为滑坡灾害链的全链条防灾减灾提供科学理论支撑.

摘要

提出了一种基于影像边缘强度图描述的SAR影像与光学影像匹配方法。首先对影像进行粗纠正,消除影像之间的尺度和旋转变化;其次,改进相位一致性特征检测方法,提取对影像相干斑噪声稳健的特征点;然后基于高斯伽玛型双边窗口比值算子计算影像边缘强度图,在此基础上构造不变特征描述符;最后联合几何约束条件,实现SAR影像与光学影像匹配。试验结果证明,与现有方法相比,本文方法能够大幅提高SAR影像与光学影像匹配结果中的正确匹配特征数量以及影像配准精度。

摘要

提出了一种基于亮度空间和相位一致性理论的多光谱遥感影像特征点检测算法。首先利用参数自适应的灰度变换函数建立影像亮度空间;然后结合相位一致性方法在影像亮度空间进行候选特征点检测,并将候选特征点映射到原始影像上进行非极大值抑制;最后在尺度空间计算特征点的特征尺度值。本文方法有效结合了亮度空间特征检测和相位一致性特征检测的优势,对多光谱遥感影像的辐射变化具有较强的稳健性。试验结果证明,与传统特征点检测算法相比,本文方法在特征重复率和重复特征数量方面都具有明显的优势。

摘要

倾斜摄影测量进行三维模型重建时，由于影像匹配精度和密集点云简化等因素，使得三角形网格模型表面的法向量存在许多明显噪声，加上镜头畸变和光照条件不同引起的影像间几何与辐射的不一致，最终导致不同三角形之间纹理映射结果不连续，这种碎片状纹理表面的真实感不强，难以直观理解。针对此，提出了一种局部区域表面一致性约束的纹理映射方法，采用区域生长策略将多个三角形合并为一个较大的平面区域，并且在区域生长过程中顾及了区域的连续性和平面性，建立该平面区域与同一影像之间的映射关系。实验证明了该方法能够有效消除纹理映射碎片化的现象。

摘要

如何在火灾态势迅速演变的复杂室内环境下选择安全有效的疏散路线是正确引导人群疏散、减少人员伤亡的重要保障。传统静态寻径方法难以顾及火灾态势演变过程，导致疏散决策的盲目性和滞后性突出。本文提出了一种实时威胁态势感知的室内火灾疏散路径动态优化方法，充分利用实时接入的火场状态和室内建筑环境状态等火灾威胁态势场信息，动态调整和优化疏散路径。该方法建立了室内火灾实时威胁态势信息在语义空间的统一表示模型，并对多源、多尺度火灾传感器观测数据在语义空间进行统一建模，从实时接入的动态观测数据中提取室内火灾三维威胁态势信息，用于约束疏散路径的动态优化。模拟试验证明，本方法可根据火灾态势演变准确可靠地动态调整疏散路径，从而显著提高应急疏散的精准性。

摘要

彭州地处成都平原与龙门山的过渡地带，土地利用状况具有强度高、类型多、复杂度大的特点，土地类型变化非常快。同时，“5·12”汶川大地震严重破坏了该区域的生态环境，这场大灾难导致了地震灾区土地利用在类型和结构上都发生了巨大变化。因此，如何快速的获取最新的土地利用信息对于灾后重建及政府决策具有重要意义。利用无人机高空间分辨率影像作为数据源，首先引入SIFT算法完成了无人机影像的自动拼接，然后采用面向对象的分析技术获取了两期无人机影像的土地利用类型，着重研究了影像最优分割尺度的获取，最后建立了土地利用动态监测系统获取了两期土地利用信息的变化量，提出了一种适用于四川盆地多云雾山地区域土地信息动态监测方法。通过对实验区两期影像的分析研究，快速获取了各类型地类的变化量，并对变化原因进行了分析。研究结果表明：利用无人机影像进行土地利用动态监测能克服多云雾山地区域卫星影像难以实时获取问题，能快速、高效的获得土地变更信息。

摘要

在深入分析无人机应急测绘任务主要特点、工作模式和主要流程的基础上,提出了任务需求语义约束的任务模板设计方法,并设计了一种统一的无人机航飞任务模板,通过在省级应急测绘指挥平台中的实际应用验证了该任务模版的正确性和有效性。

摘要

建筑物间距规划方案审批是工程质量管理中的重要步骤,传统的规划审批方案以二维CAD线划数据为基础,其在数据完整性和可视化表达方面存在明显的局限性。BIM丰富的几何语义信息和3D GIS良好的数据管理与可视化分析能力为建筑规划审批提供了更为可靠的解决方案。本文设计实现了将典型BIM数据(revit数据格式)几何及其语义集成到3D GIS的技术方案,并开发了BIM与GIS集成的建筑间距自动化审批功能,为三维环境下建筑规划审批提供了更有效与可靠的技术支撑。

摘要

我国水文气象站少且空间分布不均衡,水文模型参数难以获取极大限制了其在防洪预警中的应用。针对新安江水文模型在无水文资料地区应用的局限性,本文提出了一种基于遥感信息的新安江模型参数推求方法,实现了可率定的模型参数的推求:利用土壤特性与土地覆被遥感信息推求流域张力水蓄水容量;基于流域土地覆被遥感信息提取不透水面积比;利用流域土壤特性及叶面积指数遥感影像间接推算流域自由水蓄水容量。利用本文方法推求了老灌河流域新安江水文模型参数并进行了日径流模拟,实验结果表明,流域水文模拟中利用遥感信息推求出的模型参数的准确性可以达到80%以上。

摘要

通勤高峰期的交通拥堵在中国很多城市越来越严重。通勤高峰期城市道路交通流量的准确预测是缓解交通拥堵和建设智能交通的关键基础问题之一。针对现有道路交通流量主要依靠ORIGIN-DESTINATION调查法,成本高、效率低且结果准确性有限等难题,本文提出一种低成本高效率的方法。综合利用全市域范围内的交通、社保、参保、人口等数字城市数据,依据交通工具的服务半径和出行距离,将居民的出行方式归结为步行、公汽、轨道交通和自驾4种类型,利用轨道交通优先原则和最短路径算法分析统计私家车出行数量和轨道交通人流量,并在此基础上预测通勤高峰期内的道路交通流量。以武汉市典型数据为例,证明了该方法的有效性和可靠性。

摘要

针对灾区通讯设施破坏环境中,应急测绘指挥调度过程实时通信能力不足的问题,利用北斗卫星定位系统定位和短报文的优势,在Android平台基础上设计实现一套可以实时监控、实时反馈应急任务状态的应急测绘移动指挥终端系统,以提高应急测绘指挥调度的灵活性和可靠性。

摘要

BIM精细化三维模型中的数据是三维GIS重要的数据来源,然而两者数据模型在几何和语义上差异是阻碍BIM与GIS集成应用的重要问题。IFC与City GML分别为BIM和三维GIS领域最通用的标准数据模型,当前的数据转换工具虽然可有效地将IFC数据转为City GML数据,但还是难以顾及到City GML所有的LOD层级,存在信息丢失和几何不准确的问题。本文通过分析IFC数据模型与City GML模型中所有的建筑构件类型以及其关联的语义信息,分别建立IFC数据模型到City GML各层级的映射模型,描述了一种从BIM模型到多层次细节GIS模型的完整转换方法。并通过具体的实验数据进行了验证,保证数据转换方法的正确性以及稳健性。

摘要

The Open Geospatial Consortium (OGC) Geography Markup Language (GML) standard provides basic types and a framework for defining geo-informational data models such as CityGML and IndoorGML, which provide standard information models for 3D city modelling and lightweight indoor network navigation. Location information, which is the semantic engine that fuses big geo-information data, is however, discarded in these standards. The Chinese national standard of Indoor Multi-Dimensional Location GML (IndoorLocationGML) presented in this study can be used in ubiquitous indoor location intelligent applications for people and robots. IndoorLocationGML is intended as an indoor multi-dimensional location information model and exchange data format standard, mainly for indoor positioning and navigation. This paper introduces the standard’s main features: (1) terminology; (2) indoor location information model using a Unified Modeling Language (UML) class diagram; (3) indoor location information markup language based on GML; and (4) use cases. A typical application of the standard is then discussed. This standard is applicable to the expression, storage, and distribution of indoor multi-dimensional location information, and to the seamless integration of indoor–outdoor location information. The reference and basis are therefore relevant to publishers, managers, users, and developers of indoor navigation and location-based services (LBS).

摘要

The rapid and accurate assessment of building damage states using only post-event remote sensing data is critical when performing loss estimation in earthquake emergency response. Damaged roof detection is one of the most efficient methods of assessing building damage. In particular, airborne LiDAR is often used to detect roofs damaged by earthquakes, especially for certain damage types, due to its ability to rapidly acquire accurate 3D information on individual roofs. Earthquake-induced roof damages are categorized into surface damages and structural damages based on the geometry features of the debris and the roof structure. However, recent studies have mainly focused on surface damage; little research has been conducted on structural damage. This paper presents an original 3D shape descriptor of individual roofs for detecting roofs with surface damage and roofs exhibiting structural damage by identifying spatial patterns of compact and regular contours for intact roofs, as well as jagged and irregular contours for damaged roofs. The 3D shape descriptor is extracted from building contours derived from airborne LiDAR point clouds. First, contour clusters are extracted from contours that are generated from a dense DSM of individual buildings derived from point clouds. Second, the shape chaos indexes of contour clusters are computed as the information entropy through a contour shape similarity measurement between two contours in a contour cluster. Finally, the 3D shape descriptor is calculated as the weighted sum of the shape chaos index of each contour cluster corresponding to an individual roof. Damaged roofs are detected solely using the 3D shape descriptor with the maximum entropy threshold. Experiments using post-event airborne LiDAR point clouds of the 2010 Haiti earthquake suggest that the proposed damaged roof detection technique using the proposed 3D shape descriptor can detect both roofs exhibiting surface damage and roofs exhibiting structural damage with a high accuracy.

摘要

Least-squares matching is a standard procedure in photogrammetric applications for obtaining sub-pixel accuracies of image correspondences. However, least-squares matching has also been criticized for its instability, which is primarily reflected by the requests for the initial correspondence and favorable image quality. In image matching between oblique images, due to the blur, illumination differences and other effects, the image attributes of different views are notably different, which results in a more severe convergence problem. Aiming at improving the convergence rate and robustness of least-squares matching of oblique images, we incorporated prior geometric knowledge in the optimization process, which is reflected as the bounded constraints on the optimizing parameters that constrain the search for a solution to a reasonable region. Furthermore, to be resilient to outliers, we substituted the square loss with a robust loss function. To solve the composite problem, we reformulated the least-squares matching problem as a bound constrained optimization problem, which can be solved with bounds constrained Levenberg–Marquardt solver. Experimental results consisting of images from two different penta-view oblique camera systems confirmed that the proposed method shows guaranteed final convergences in various scenarios compared to the approximately 20–50% convergence rate of classical least-squares matching.

摘要

Combined bundle adjustment is a fundamental step in the processing of massive oblique images. Traditional bundle adjustment designed for nadir images gives identical weights to different parts of image point observations made from different directions, due to the assumption that the errors in the observations follow the same Gaussian distribution. However, because of their large tilt angles, aerial oblique images have trapezoidal footprints on the ground, and their areas correspond to conspicuously different ground sample distances. The errors in different observations no longer conform to the above assumption, which leads to suboptimal bundle adjustment accuracy and restricts subsequent 3D applications. To model the distribution of the errors correctly for the combined bundle adjustment of oblique images, this paper proposes an asymmetric re-weighting method. The scale of each pixel is used to determine a re-weighting factor, and each pixel is subsequently projected onto the ground to identify another anisotropic re-weighting factor using the shape of its quadrangle. Next, these two factors are integrated into the combined bundle adjustment using asymmetric weights for the image point observations; greater weights are assigned to observations with fine resolutions, and those with coarse resolutions are penalized. This paper analyzes urban and rural images captured by three different five-angle camera systems, from both proprietary datasets and the ISPRS/EuroSDR benchmark. The results reveal that the proposed method outperforms the traditional method in both back-projected and triangulated precision by approximately 5–10% in most cases. Furthermore, the misalignments of point clouds generated by the different cameras are significantly alleviated after combined bundle adjustment.

摘要

RGB-D sensors (sensors with RGB camera and Depth camera) are novel sensing systems that capture RGB images along with pixel-wise depth information. Although they are widely used in various applications, RGB-D sensors have significant drawbacks including limited measurement ranges (e.g., within 3 m) and errors in depth measurement increase with distance from the sensor with respect to 3D dense mapping. In this paper, we present a novel approach to geometrically integrate the depth scene and RGB scene to enlarge the measurement distance of RGB-D sensors and enrich the details of model generated from depth images. First, precise calibration for RGB-D Sensors is introduced. In addition to the calibration of internal and external parameters for both, IR camera and RGB camera, the relative pose between RGB camera and IR camera is also calibrated. Second, to ensure poses accuracy of RGB images, a refined false features matches rejection method is introduced by combining the depth information and initial camera poses between frames of the RGB-D sensor. Then, a global optimization model is used to improve the accuracy of the camera pose, decreasing the inconsistencies between the depth frames in advance. In order to eliminate the geometric inconsistencies between RGB scene and depth scene, the scale ambiguity problem encountered during the pose estimation with RGB image sequences can be resolved by integrating the depth and visual information and a robust rigid-transformation recovery method is developed to register RGB scene to depth scene. The benefit of the proposed joint optimization method is firstly evaluated with the publicly available benchmark datasets collected with Kinect. Then, the proposed method is examined by tests with two sets of datasets collected in both outside and inside environments. The experimental results demonstrate the feasibility and robustness of the proposed method.

摘要

Textureless and geometric discontinuities are major problems in state-of-the-art dense image matching methods, as they can cause visually significant noise and the loss of sharp features. Binary census transform is one of the best matching cost methods but in textureless areas, where the intensity values are similar, it suffers from small random noises. Global optimization for disparity computation is inherently sensitive to parameter tuning in complex urban scenes, and must compromise between smoothness and discontinuities. The aim of this study is to provide a method to overcome these issues in dense image matching, by extending the industry proven Semi-Global Matching through 1) developing a ternary census transform, which takes three outputs in a single order comparison and encodes the results in two bits rather than one, and also 2) by using texture-information to self-tune the parameters, which both preserves sharp edges and enforces smoothness when necessary. Experimental results using various datasets from different platforms have shown that the visual qualities of the triangulated point clouds in urban areas can be largely improved by these proposed methods.

摘要

RGB-D sensors are novel sensing systems that capture RGB images along with pixel-wise depth information. Although they are widely used in various applications, RGB-D sensors have significant drawbacks with respect to 3D dense mapping of indoor environments. First, they only allow a measurement range with a limited distance (e.g., within 3 m) and a limited field of view. Second, the error of the depth measurement increases with increasing distance to the sensor. In this paper, we propose an enhanced RGB-D mapping method for detailed 3D modeling of large indoor environments by combining RGB image-based modeling and depth-based modeling. The scale ambiguity problem during the pose estimation with RGB image sequences can be resolved by integrating the information from the depth and visual information provided by the proposed system. A robust rigid-transformation recovery method is developed to register the RGB image-based and depth-based 3D models together. The proposed method is examined with two datasets collected in indoor environments for which the experimental results demonstrate the feasibility and robustness of the proposed method

摘要

Improving the matching reliability of low-altitude images is one of the most challenging issues in recent years, particularly for images with large viewpoint variation. In this study, an approach for low-altitude remote sensing image matching that is robust to the geometric transformation caused by viewpoint change is proposed. First, multiresolution local regions are extracted from the images and each local region is normalized to a circular area based on a transformation. Second, interest points are detected and clustered into local regions. The feature area of each interest point is determined under the constraint of the local region which the point belongs to. Then, a descriptor is computed for each interest point by using the classical scale invariant feature transform (SIFT). Finally, a feature matching strategy is proposed on the basis of feature similarity confidence to obtain reliable matches. Experimental results show that the proposed method provides significant improvements in the number of correct matches compared with other traditional methods.

摘要

飞行器航路前方的“威胁态势图”

面向飞行器导航需求,针对传统空地环境警告信息繁杂导致情境意识薄弱和决策时间长等瓶颈问题,建立了机场环境威胁态势信息在语义空间的统一表示模型,提出了对多源、多尺度、多种分布类型的机场空地环境信息在语义空间的统一建模与动态更新方法,实现了从实时接入的动态观测数据中深度搜索威胁态势信息,并达到信息快速组织与检索的目的。从林芝机场的数据建模和实验结果表明,该方法能精准、高效的建立面向飞行器导航应用的动态机场环境威胁态势图。

摘要

针对公共安全应急响应中支持推理、挖掘和关联分析的地理视频建模难题,提出了一种显式表达视频变化的多层次地理视频语义模型,并用UML图进行描述.该模型的特点是：改变了传统视频流整体语义描述方法,通过面向变化的三域（特征域-行为过程域-事件域）定义地理视频语义的层次结构和数据的层次表达;在各层次语义描述中将地理环境语义与视频内容语义有机结合,支持多地理视频数据的关联表示.以公共安全事件监控视频为例阐明了模型的实用性和有效性.

摘要

为兼顾时空索引方法的空间利用率、时间效率和查询种类,提出了一种新的轨迹数据索引方法-HBSTR树.其基本思想是：轨迹采样点以轨迹节点的形式成组集中管理,哈希表用于维护移动目标的最新轨迹节点,轨迹节点满后作为叶节点插入时空R 树,另外采用B 树对轨迹节点构建一维索引,既有利于提升索引创建效率,又同时满足时空条件搜索和特定目标轨迹搜索等多种查询类型.为提升时空查询效率,提出了新的时空R 树评价指标和节点选择子算法改进时空R 树插入算法,同时提出了一种时空R树的数据库存储方案.试验结果表明,HBSTR 树在创建效率、查询效率和支持查询类型等方面综合性能优于现有方法,支持大规模实时轨迹数据库的动态更新和高效访问.

摘要

建筑信息模型(BIM)与地理信息系统(GIS)集成，不仅使得精细化的三维模型得到极大重用，同时两者的数据集成和共享可实现从几何到物理和功能特性的多尺度综合表达，已经成为新一代数字城市三维建模的关键途径之一。本文选取典型的BIM模型数据格式(RVT)，提出语义约束的RVT模型到CityGML模型的转换方法，以BIM模型丰富的语义信息为约束实现几何简化及转换，同时实现了几何部件与语义信息的一一映射及语义输出，并以建筑模型、暖通、桥梁模型为例进行了验证。

摘要

With the goal to achieve an accuracy navigation within the building environment, it is critical to explore a feasible way for building the connectivity relationships among 3D geographical features called in-building topology network. Traditional topology construction approaches for indoor space always based on 2D maps or pure geometry model, which remained information insufficient problem. Especially, an intelligent navigation for different applications depends mainly on the precise geometry and semantics of the navigation network. The trouble caused by existed topology construction approaches can be smoothed by employing IFC building model which contains detailed semantic and geometric information. In this paper, we present a method which combined a straight media axis transformation algorithm (S-MAT) with IFC building model to reconstruct indoor geometric topology network. This derived topology aimed at facilitating the decision making for different in-building navigation. In this work, we describe a multi-step deviation process including semantic cleaning, walkable features extraction, Multi-Storey 2D Mapping and S-MAT implementation to automatically generate topography information from existing indoor building model data given in IFC.

摘要

Indoor navigation is increasingly widespread in complex indoor environments, and indoor path planning is the most important part of indoor navigation. Path planning generally refers to finding the most suitable path connecting two locations, while avoiding collision with obstacles. However, it is a fundamental problem, especially for 3D complex building model. A common way to solve the issue in some applications has been approached in a number of relevant literature, which primarily operates on 2D drawings or building layouts, possibly with few attached attributes for obstacles. Although several digital building models in the format of 3D CAD have been used for path planning, they usually contain only geometric information while losing abundant semantic information of building components (e.g. types and attributes of building components and their simple relationships). Therefore, it becomes important to develop a reliable method that can enhance application of path planning by combining both geometric and semantic information of building components. This paper introduces a method that support 3D indoor path planning with semantic information.

摘要

With the rapid development of sensor networks and Earth observation technology, a large quantity of disaster-related data is available, such as remotely sensed data, historic data, case data, simulated data, and disaster products. However, the efficiency of current data management and service systems has become increasingly difficult due to the task variety and heterogeneous data. For emergency task-oriented applications, the data searches primarily rely on artificial experience based on simple metadata indices, the high time consumption and low accuracy of which cannot satisfy the speed and veracity requirements for disaster products. In this paper, a task-oriented correlation method is proposed for efficient disaster data management and intelligent service with the objectives of 1) putting forward disaster task ontology and data ontology to unify the different semantics of multi-source information, 2) identifying the semantic mapping from emergency tasks to multiple data sources on the basis of uniform description in 1), and 3) linking task-related data automatically and calculating the correlation between each data set and a certain task. The method goes beyond traditional static management of disaster data and establishes a basis for intelligent retrieval and active dissemination of disaster information. The case study presented in this paper illustrates the use of the method on an example flood emergency relief task.

摘要

Public security incidents have been increasingly challenging to address with their new features, including large-scale mobility, multi-stage dynamic evolution, spatio-temporal concurrency and uncertainty in the complex urban environment, which require spatio-temporal association analysis among multiple regional video data for global cognition. However, the existing video data organizational methods that view video as a property of the spatial object or position in space dissever the spatio-temporal relationship of scattered video shots captured from multiple video channels, limit the query functions on interactive retrieval between a camera and its video clips and hinder the comprehensive management of event-related scattered video shots. GeoVideo, which maps video frames onto a geographic space, is a new approach to represent the geographic world, promote security monitoring in a spatial perspective and provide a highly feasible solution to this problem. This paper analyzes the large-scale personnel mobility in public safety events and proposes a multi-level, event-related organization method with massive GeoVideo data by spatio-temporal trajectory. This paper designs a unified object identify(ID) structure to implicitly store the spatio-temporal relationship of scattered video clips and support the distributed storage management of massive cases. Finally, the validity and feasibility of this method are demonstrated through suspect tracking experiments.

摘要

Dynamic flood disaster simulation is an emerging and promising technology significantly useful in urban planning, risk assessment, and integrated decision support systems. It is still an important issue to integrate the large assets such as dynamic observational data, numerical flood simulation models, geographic information technologies, and computing resources into a unified framework. For the intended end user, it is also a holistic solution to create computer interpretable representations and gain insightful understanding of the dynamic disaster processes, the complex impacts, and interactions of disaster factors. In particular, it is still difficult to access and join harmonized data, processing algorithms, and models that are provided by different environmental information infrastructures. In this paper, we demonstrate a virtual geographic environments-based integrated environmental simulation framework for flood disaster management based on the notion of interlinked resources, which is capable of automated accumulating and manipulating of sensor data, creating dynamic geo-analysis and three-dimensional visualizations of ongoing geo-process, and updating the contents of simulation models representing the real environment. The prototype system is evaluated by applying it as a proof of concept to integrate in situ weather observations, numerical weather and flood disaster simulation models, visualization, and analysis of the real time flood event. Case applications indicate that the developed framework can be adopted for use by decision-makers for short-term planning and control since the resulting simulation and visualization are completely based on the latest status of environment.

Abstract

Abstract

三维GIS 是当今乃至未来GIS 技术的主要标志性内容之一，它突破了空间信息在二维地图平面中单调表现 的束缚，为各行各业以及人们的日常生活提供了更有效的辅助决策支持。本文重点介绍了三维GIS 的数据模型、 数据库管理和可视化分析等关键技术及其研究进展，并以武汉市为例展示了三维GIS 对城市立体空间的整体表 达，为大城市、全市域的三维数字城市建设奠定了基础，最后探讨了在智慧城市建设与城市安全中三维GIS将发挥 日益重要的时空信息承载引擎与空间智能技术支撑作用。

Abstract

以“4·20”芦山7.0级强烈地震中应急测绘保障为例,系统分析了目前应急测绘保障工作的机制,以及数据获取、传输、处理、发布以及应急测绘数据共享多个环节中存在的突出问题,提出了一种新的应急测绘保障体系架构和任务驱动的聚焦服务机制。

Abstract

基于三维建筑空间表达充分结合建筑防火专题语义信息建立了面向建筑物内部空间划分与通达性分析的一体化语义描述并结合防火部件层次的动态特征发展面向室内火灾动态疏散过程的三维建筑信息模型从而辅助火灾应急疏散的三维空间逃生分析 基于实验构建的三维建筑信息模型及其基于语义的动态联通网络证明了其在室内火灾动态疏散中的特殊价值

Abstract

为实现大规模地形景观和精细工程设施模型在三维GIS中的无缝集成管理,并支持工程设施全生命周期的共享应用,提出了一种可根据设计参数自动建立复杂设施三维模型并交互式编辑修改的方法,扩展了三维GIS数据模型,实现了三维几何模型与其参数信息的有机集成与同步更新,并以桥梁模型的构建为例验证了该方法的可行性和有效性。

Abstract

近年来,建筑信息模型(BIM)与地理信息系统(GIS)的集成应用越来越广泛且深入,不同专业领域通过简单模型转换实现信息交互的方法由于只保留了少量的语义信息从而导致了应用的分散和独立,局限性十分明显.IFC和CityGML分别为BIM和GIS领域内通用的数据模型标准,两者之间的几何和语义信息共享将为BIM和GIS的集成奠定基础.本文基于IFC和CityGML标准,提出IFC几何要素过滤方法以及IFC到CityGML的语义映射规则,为IFC与CityGML建筑模型的几何、语义信息互操作提供一种通用手段,并通过实例进行了验证.

Abstract

商业中心、交通枢纽、医院、停车场等复杂室内及地下空间的安全管理与应急响应对室内外无缝导航与位置服务的需求日益迫切,提出了一种室内位置信息模型,扩展了OGC标准CityGML和IndoorGML中的位置信息描述,提供了描述室内相对位置和室内绝对位置的本体,介绍了一种针对三维建筑物模型的室内空间自动提取方法,为智能位置服务奠定了重要基础。

Abstract

传统基于“图层付象”的组织方法，没有考虑三维城市模型的不同内容以及不同细节层次的粒度差 异，导致在网络环境下的传输效率低，难以满足多用户并发访问的流畅可视化。深入分析了大范围漫游与小 范围聚焦的用户体验特点，通过元数据统筹管理和对象离散化，即时响应用户请求，减少无效数据传输，保证 了多用户并发环境下的高效调度和浏览。针对模型LoI)和分解的对象，设计了结构统一的对象ID,隐式存储 关联关系并支持分布式模型存储管理。以分布式数据库MongoDB为平台进行实验，验证了本文方法的可行 性和有效性。

The task-oriented FSM of the IDISS

Abstract

The Chinese Government and citizens face enormous challenges of disaster management as widespread devastation, economic damages, and loss of human lives caused by increasing natural disasters. Disaster management requires a complicated iterative process that includes disaster monitoring, early detection, forecasting, loss assessment, and efficient analysis of disaster reduction. Each task typically involves the use of technologists and multiple geospatial information resources, including sensors, data sources, models, geo-tools, software packages, and computing resources. However, most existing disaster management systems operate in a typical passive data-centric mode, where resources cannot be fully utilized. This impediment is partially being addressed by the increasingly complex application requirements and the growing availability of diverse resources. In this paper, we summarize and analyze the practical problems experienced by the National Disaster Reduction Application System of China. To address the issues of data-centric, centralized, isolated solutions, we propose a novel Focusing Service Mechanism, which is capable of scheduling and allocating for optimum utilization of multiple resources, to dynamically generate collaborative and on-demand disaster information services. We also demonstrate the design and implementation of the Integrated Disaster Information Service System (IDISS). Through the service strategies of Virtualizing, Wrapping, and Integrating, disaster-related resources are constructed into services in the IDISS. These services are dynamically aggregated into focusing service chains, for diverse disaster management tasks. Actual applications illustrate that the proposed service system can significantly improve the capability of disaster management in China.

Structure of a complete VGE

Abstract

Abstract Virtual Geographic Environments (VGEs) are proposed as a new generation of geographic analysis tool to contribute to human understanding of the geographic world and assist in solving geographic problems at a deeper level. The development of VGEs is focused on meeting the three scientific requirements of Geographic Information Science (GIScience) — multi-dimensional visualization, dynamic phenomenon simulation, and public participation. To provide a clearer image that improves user understanding of VGEs and to contribute to future scientific development, this article reviews several aspects of VGEs. First, the evolutionary process from maps to previous GISystems and then to VGEs is illustrated, with a particular focus on the reasons VGEs were created. Then, extended from the conceptual framework and the components of a complete VGE, three use cases are identified that together encompass the current state of VGEs at different application levels: 1) a tool for geo-object-based multi-dimensional spatial analysis and multi-channel interaction, 2) a platform for geo-process-based simulation of dynamic geographic phenomena, and 3) a workspace for multi-participant-based collaborative geographic experiments. Based on the above analysis, the differences between VGEs and other similar platforms are discussed to draw their clear boundaries. Finally, a short summary of the limitations of current VGEs is given, and future directions are proposed to facilitate ongoing progress toward forming a comprehensive version of VGEs.

Abstract

The difference between real-time CSCW systems and traditional distributed systems is that the former one is supposed to provide a natural, free and fast interface for multi-user interaction. However, the typical multi-user interaction method applied in 3D CAD systems is strict consistency maintenance, such as locking mechanism and floor control, which may generate a stagnant and unnatural interface. This paper proposes a 3D semanticbased Operational transformation (OT) to support less constrained multi-user interaction and to achieve consistency in collaborative CAD editing (co-CAD) systems, and it can be used in many collaborative CAD/CAM industries.

Abstract

A complex 3D city model contains detailed descriptions of both its appearance and its internal structure, including architectural components. Because of the topological complexity and the large volumes of data in such models, profiling is an effective method to present the internal structure, the distributed characteristics, and the hierarchical relationships of the model to provide intuitive visual information to the viewer and to reveal the relationships between the elements of the model and the whole. However, with commonly used boundary descriptions, it is difficult to comprehensively preserve the consistency of three-dimensional profiling using existing algorithms based on geometric constraints. This paper proposes a novel semantics-constrained profiling approach to ensure the consistency of the geometrical, topological, and semantic relationships when profiling complex 3D city models. The approach transforms the 3D model’s boundary description, defined using the CityGML standard of the Open Geospatial Consortium (OGC), into a set of unified volumetric features described as solids. This approach is characterized by (1) the use of the concepts of semantic relationships, virtual edges, and virtual surfaces; (2) the semantic analysis of 3D models and the extraction of volumetric features as basic geometric analytic units; (3) the completion of structural connectivity and space coverage for each volumetric feature, which is represented as a solid model; and (4) the use of a reliable 3D Boolean operation for efficient and accurate profiling. A typical detailed 3D museum model is used as an example to illustrate the profiling principle, and the experimental results demonstrate the correctness and effectiveness of this approach.

Abstract

Highly detailed surface models and their real-time applications are increasingly popular in architecture, construction and other design and engineering fields. However, new and related problems have emerged concerning the efficient management of the resulting large datasets and the seamless integration of heterogeneous data. Moreover, the increasingly common requirements of local high-fidelity modeling combined with large-scale landscapes lead to difficulty in the seamless multi-resolution representation of hybrid triangulated irregular networks (TINs) and Grids. This paper presents a hybrid data structure with high-efficiency and a related organizational method for the seamless integration of multi-resolution models. This approach is characterized by (1) a self-adaptive algorithm for feature-preserving surface partitioning, (2) an efficient hybrid index structure for combined Grid and TIN surfaces, and (3) a view-dependent scheduling strategy with access to Grids of necessary resolution, giving priority to the dynamic loading of TINs. Experiments using typical real design datasets of highway constructions are able to achieve accuracy-preserved and real-time availability of results that prove the validity and efficiency of this approach.

Abstract

GIS is now faced with the challenge how to represent and understand the fast-paced, constantly changing world, given increasingly real-time data including readings from large-scale distributed sensors and large quantities of simulation data generated by computation models. Traditional static GIS pays more attention to representing historic data and Temporal GIS(TGIS) only treats time as a occasional but not critical factor and can't support the explicit change representation. In this context, Real-time GIS(RGIS) is put forward and its data model becomes a key problem how to make an appropriate abstraction over the rapid changes implied in real-time data stream and establish the general interaction relationship between them. The paper proposes a spatiotemporal changeoriented three-domain model with the emphasis on the semantic interaction relationship of object, event and process. Based on this model, a semantic enrichment method for multi-scale spatiotemporal change is put forward. Finally, as a RGIS application, indoor fire disaster simulation is illustrated and proves the validity of the proposed model.

Abstract

Aiming at the increasing requirements of seamless indoor and outdoor navigation and location service, a Chinese standard of Multidimensional Indoor Location Information Model is being developed, which defines ontology of indoor location. The model is complementary to 3D concepts like CityGML and IndoorGML. The goal of the model is to provide an exchange GML-based format for location needed for indoor routing and navigation. An elaborated user requirements analysis and investigation of state-of-the-art technology in expressing indoor location at home and abroad was completed to identify the manner humans specify location. The ultimate goal is to provide an ontology that will allow absolute and relative specification of location such as "in room 321", "on the second floor", as well as, "two meters from the second window", "12 steps from the door"

Abstract

Research in support of indoor mapping and modelling (IMM) has been active for over thirty years. This research has come in the form of As-Built surveys, Data structuring, Visualisation techniques, Navigation models and so forth. Much of this research is founded on advancements in photogrammetry, computer vision and image analysis, computer graphics, robotics, laser scanning and many others. While IMM used to be the privy of engineers, planners, consultants, contractors, and designers, this is no longer the case as commercial enterprises and individuals are also beginning to apply indoor models in their business process and applications. There are three main reasons for this. Firstly, the last two decades have seen greater use of spatial information by enterprises and the public. Secondly, IMM has been complimented by advancements in mobile computing and internet communications, making it easier than ever to access and interact with spatial information. Thirdly, indoor modelling has been advanced geometrically and semantically, opening doors for developing user-oriented, context-aware applications. This reshaping of the public’s attitude and expectations with regards to spatial information has realised new applications and spurred demand for indoor models and the tools to use them. This paper examines the present state of IMM and considers the research areas that deserve attention in the future. In particular the paper considers problems in IMM that are relevant to commercial enterprises and the general public, groups this paper expects will emerge as the greatest users IMM. The subject of indoor modelling and mapping is discussed here in terms of Acquisitions and Sensors, Data Structures and Modelling, Visualisation, Applications, Legal Issues and Standards. Problems are discussed in terms of those that exist and those that are emerging. Existing problems are those that are currently being researched. Emerging problems are those problems or demands that are expected to arise because of social changes, technological advancements, or commercial interests. The motivation of this work is to define a set of research problems that are either being investigated or should be investigated. These will hopefully provide a framework for assessing progress and advances in indoor modelling. The framework will be developed in the form of a problem matrix, detailing existing and emerging problems, their solutions and present best practices. Once the framework is complete it will be published online so that the IMM community can discuss and modify it as necessary. When the framework has reached a steady state an empirical benchmark will be provided to test solutions to posed problems. A yearly evaluation of the problem matrix will follow, the results of which will be published.

Abstract

洪涝灾害损失评估是防洪减灾科学决策的基础，其中洪水淹没分析是准确提取洪水淹没范围、水深及历时等灾情信息的关键。洪水淹没分析主要采用数字高程模型数据（DEM），由于DEM的格网分辨率与高程精度有限，常出现异常的洼地或平地，导致难以可靠计算每个格网点处的流向，而传统方法采用统一高程的洼地填平处理又使得容易出现洪水演进过程中复杂起伏地形水面爬坡以及平坦地形水位断流的问题，为此本文提出了顾及流速和淹没时间的自适应逐点水位修正算法，即在DEM坡面流模拟的基础上，根据洪水水流特性、地形、边界变化、水流速度、水深变化以及淹没点的淹没时间，计算水位修正值，对洪水演进过程中每个格网点的水位进行修正，采用多种地貌类型的DEM数据进行实验，证明洪水演进的淹没范围、水深及历时的实时计算结果准确可靠，可为快速评估灾害损失与防洪决策服务提供更为科学的依据。

Abstract

Typical characteristics of remote sensing applications are concurrent tasks, such as those found in disaster rapid response. The existing composition approach to geographical information processing service chain, searches for an optimisation solution and is what can be deemed a “selfish” way. This way leads to problems of conflict amongst concurrent tasks and decreases the performance of all service chains. In this study, a non-cooperative game-based mathematical model to analyse the competitive relationships between tasks, is proposed. A best response function is used, to assure each task maintains utility optimisation by considering composition strategies of other tasks and quantifying conflicts between tasks. Based on this, an iterative algorithm that converges to Nash equilibrium is presented, the aim being to provide good convergence and maximise the utilisation of all tasks under concurrent task conditions. Theoretical analyses and experiments showed that the newly proposed method, when compared to existing service composition methods, has better practical utility in all tasks.

Abstract

The real-time visualization of 3D GIS at a whole city scale always faces the challenge of dynamic data loading with high-efficiency. Based on the multi-tier distributed 3D GIS framework, this paper presents a multi-level cache approach for dynamic data loading. It aims to establish in 3D GIS spatial database engine (3DGIS-SDE) the unified management mechanism of caches on three levels, including: the client memory cache (CMC) oriented to sharing application, the client file cache (CFC) organized by index, as well as the application server memory cache (ASMC) of structural consistency. With the help of the proposed optimized cache replacement policy, multi-level cache consistency maintenance as well as multithread loading model designed in the paper, the engine is able to adaptively make full use of each-level caches according to their own application properties and achieve effective coordination between them. Finally, a practical 3D GIS database based on Oracle 11g is employed for test. The experimental results prove this approach could satisfy multi-user concurrent applications of 3D visual exploration.

Abstract

针对飞行器可视导航中复杂空地环境时空要素统一精准表示的难题，本文提出了面向飞行器可视导航的复杂空地环境动态3维表示的GIS数据模型和相应的时刻数据存储结构，并用UML图进行了描述。该模型综合考虑了复杂空地环境要素多维、动态、边界模糊等特点，刻画了多维动态时空数据在空间、时间、尺度、语义四个方面的特征及其相互关系。最后，以某机场的空地环境数据的组织、分析和可视化为例，验证了该模型的实用性。

Abstract

面向大型土木工程设计,提出了一种运用WMS共享空间数据源并实现高效应用集成的工程设计应用技术体系。首先,直接针对WMS数据服务器定向开发数据获取应用,通过高效并行多线程实现空间数据的分块网络传输,同时结合本地缓存机制与网络共享,实现了一种双轨存储访问机制;其次,基于独立的应用下载与嵌入的实时线程分配,实现了远程数据的本地化模拟应用环境与分布式共享协同;再次,针对WMS数据的应用,实现了空间数据向工程数据的高精度转换与工程制图出图体系,开发了统一的全球三维可视化平台,用于直观地综合表达各种WMS数据源。

Abstract

车载激光扫描点云数据已经成为数字城市和危机管理等领域越来越重要的三维空间信息源,针对大规模点云数据高效管理的技术瓶颈,提出一种八叉树和三维R树集成的空间索引方法——3DOR树,充分利用八叉树的良好收敛性创建R树叶节点,避免逐点插入费时过程,同时R树平衡结构保证良好的数据检索效率。并还扩展R树结构生成多细节层次（LOD）点云模型,提出一种支持缓存的多细节层次点云数据组织方法。试验证明,该方法具有良好的空间利用率和空间查询效率,支持多细节层次描述能力和数据缓存机制,可应用于大规模点云数据的后处理与综合应用。

Abstract

Many 3D GIS applications require 3D building models with different LoD (Level of Detail) that satisfy certain quality criteria. However, because of their complexity, most detailed 3D building models available are still produced manually, which results in inevitable geometric and topological errors. These errors hinder the downstream processing of such models. And existing researches on LoD production either focus on the simplification of smooth polygonal mesh or the generalization of regular prismatic building models. The generalization of detailed 3D building models is still immature. Aiming at producing cleaned models of different LoD for existing hand-made 3D building models, this paper starts by investigating two typical modeling errors of such models, incompleteness and separation. Repair methods with reasonable assumptions of buildings are then proposed for each type of errors. The generalization method based on morphological operations is then employed, coupled with model repair, to generate error-free simplified models.

Abstract

Spatial data balancing distribution can evidently improve the performance of parallel spatial database in shared nothing parallel architecture. Considering spatial locality and unstructured variable length characteristics of spatial data, this paper proposes a dynamic spatial data balancing distribution method under shared nothing parallel database environment. By using Hilbert ordering code to keep spatial locality relationship between spatial objects, the presented method can fulfill spatial data static balancing distribution status, which depends on hierarchically decomposing Hilbert space-filling curve code to allocate approximately even spatial data volume to parallel nodes in distributed network. Then spatial proximity index is introduced to resolve spatial data unbalancing problem caused by spatial database dynamic updating. Through moving spatial data fragments to goal node which is the minimum spatial proximity with data moving out node, the spatial database redistributing strategy can attain dynamic data balance among all network parallel nodes. Our experimental results show that the proposed method can effectively improve parallel performance deterioration resulted from spatial data unbalancing and achieve spatial data dynamic balancing distribution in parallel spatial database.

Abstract

多细节层次表达是三维GIS的重要特征之一。为提高细节层次模型的管理效率，本文提出一种扩展多细节层次功能的三维R树索引方法，通过全局优化和三维聚类分析建立动态三维R树索引，研制了先自下而上、后自上而下全局搜索的节点选择算法和基于k-medoids聚类算法的节点分裂算法，保证节点尺寸均匀、形状规则以及重叠减少。基于良好的三维树形结构，本文扩展了传统的三维R树索引结构，实现R树索引和细节层次模型的无缝集成。为验证本文方法的有效性，通过仿真实验，结果证明了本文方法能很大程度地提升多细节层次三维城市模型数据库的空间查询效率，具有较好的应用前景和实用价值。

Abstract

三维模型多细节层次的自适应控制是三维GIS和虚拟环境等领域研究的难点问题之一，针对大规模三维城市建模需要，本文介绍了一种基于三维R树索引的多细节层次(以下简称LOD)管理方法，从叶节点层向根节点自动生成LOD模型，并设计实现了视锥体查询和LOD检索的算法。通过实验分析，证明本文的LOD定义参数能够定量调整场景复杂度，进而自适应控制三维模型可视化的细节层次，适合建筑物类型地物的LOD描述。

Abstract

针对大规模三维城市建模与数据库协同应用,设计实现了一种高效的三维GIS数据库引擎,支持基于Oracle 11g的多模式数据库管理;提出了顾及语义的三维空间数据库模型,为地上下室内外三维空间数据的一体化组织管理奠定了基础。介绍了该引擎涉及的多层次三维空间索引、多级缓存、多线程调度以及异步通信传输等关键技术,并用武汉市三维城市模型数据进行了试验分析,验证了该引擎的有效性和可靠性。

Abstract

从基本概念、应用需求和技术动态等方面就3维GIS技术的发展与演进进行了简要评述，强调了专业化与大众化两种应用对3维GIS提出的不同挑战。

Abstract

Aiming at the integrative management and comprehensive applications of large-scale 3D geospatial information covering the full 3D space of a city, this paper briefly introduces the design and implementation of a full 3D GIS platform: GeoScope, which provides a professional solution for the massive full three-dimensional geospatial data integration, management, analysis, visualization, and applications. GeoScope is characterized by: (1) extendible software architecture based on the hierarchical message bus, facilitates multimodal integrative applications of 2D GIS and 3D GIS; (2) unified 3D city models, support multiscale semantic representation of outdoor & indoor and aboveground & underground 3D objects; (3) high-efficient 3D geospatial database engine, supports integrated management of massive 3D geospatial data for real-time applications; and (4) high-performance visualization engine exploiting the massively parallel computation architecture of modern GPUs, supports real-time realistic rendering of large-scale complicated 3D geospatial environments. The successful pilot application of GeoScope is also illustrated with the 3D city models of 8494 km2 of the whole Wuhan City, the largest city in middle China.

Abstract

Web services make tools which used to be merely accessible to the specialist available to all, and permitting previous manual data processing and analysis tasks to be automated. One of key problem is Web services composition in terms of Quality of Service (QoS). There are many task concurrencies, such as remote sensing image processing, in computation-intensive scientific applications. However, existing Web service optimal combination approaches are mainly focused on single tasks by using "selfish" behavior to pursue optimal solutions. This causes conflicts because many concurrent tasks are competing for limited optimal resources, and the reducing of service quality in services. Based on the best reply function of quantified task conflicts and game theory, this paper establishes a mathematical model to depict the competitive relationship between multitasks and Web service under QoS constraints and it guarantees that every task can obtain optimal utility services considering other task combination strategies. Moreover, an iterative algorithm to reach the Nash equilibrium is also proposed. Theory and experimental analysis show the approach has a fine convergence property, and can considerably enhance the actual utility of all tasks when compared with existing Web services combinatorial methods. The proposed approach provides a new path for QoS-aware Web service with optimal combinations for concurrent tasks.

Description of hierarchical levels of detail

Abstract

Aiming at the increasing critical issues of existing 2D plans and map‐based methodology for integrated management of advanced buildings and related dynamic property rights in complicated 3D built environments, a novel semantics‐based 3D dynamic house property model with hierarchical levels of detail is proposed in this paper, based on comprehensive analysis of 3D house property objects and various application requirements. This model is characterized by: (1) 3D geometric semantics: a 3D geometry hierarchy of exterior and interior of buildings is defined; (2) thematic semantics, comprehensive house property object and related property right relationships are illustrated; (3) temporal semantics, dynamic representation of house property driven by both geometric events and property right events is involved. This model facilitates comprehensive data mining to analyze spatial relationships and dynamic change of property rights in real 3D built environments and can also support the sale and lease of real estate, facility management, house planning and so on.

The comparison results of a facade (Eq represents equal interval and exp represents exponential interval)

Abstract

Aiming at the fundamental issue of optimal design of discrete levels of detail (LOD) for the visualization of complicated 3D building façades, this paper presents a new quantitative analytical method of perceptible 3D details based on perceptual metric. First, the perceptual metric is defined as the quantitative indicator of the visual perceptibility of façade details at a given viewing distance. Then, according to the human vision system, an algorithm employing 2D discrete wavelet transform and contrast sensitivity function is developed to extract the value of perceptual metric from the rendered image of the façade. Finally, a perceptual metric function is defined, based on the perceptual metric values extracted at equal interval viewing distances. The minimum detail redundancy model is then proposed for the optimal design of discrete LODs. This method provides a quantitative instruction for generating discrete LODs. The experimental results prove the effectiveness and great potential of this method.

Abstract

In recent years, the necessity of the incorporation of semantic information into three-dimensional city models (3DCMs) has become a consensus in 3D GIS field. In order to provide practical support for visual applications concerned with semantics, this paper firstly presents an extended semantic model based on the CityGML standard, which was worked out for the general storage and representation of semantics. In this model, concepts like Room, Corridor and Stair are all derived from concept Space which corresponds to the concept of Room in CityGML. This extension will benefit the indoor structure representation. Geological feature is also supported by the model for the underground analysis. Next, for the promotion of semantic modeling by this model, a semi-automatic process of semantic enrichment is implemented in a data integration tool. It provides an adaptive way to link semantics with pure geometry. Finally, two typical cases of visual exploration are illustrated to prove the model's practicability in a national 3D GIS project of China. One is indoor routing, which adopts this model to extract the geometric path and thus enrich traditional semantic-enhanced navigation routine; another case is unified profiler, where semantics are intergrated in order to fill up the cross section correctly and ensure the topological and semantic consistency.

Abstract

To improve the reusability of three-dimensional (3D) models and simplify the complexity of natural scene reconstruction, this paper presents a 3D model database for universal 3D GIS. After the introduction of its extensible function architecture, accompanied by the conclusion of implicit spatial-temporal hierarchy of models in any reconstructed scene of 3D GIS for general purpose, several key issues are discussed in detail, such as the storage and management of 3D models and related retrieval and load method, as well as the interfaces for further on-demand development. Finally, the validity and feasibility of this model database are proved through its application in the development of 3D visualization system of railway operation.

Abstract

In this paper, a novel method, namely contextual routing and navigation, is proposed. This method is based on the author's proposed hierarchical, lane-oriented 3D road network. The key to implement contextual routing and navigation is to adopt cognition-based hierarchical routing strategy and the view-based multi-scale navigation strategy. The two strategies enable users routing on roadway centreline, carriageway or lane and provides 2D, 2.5D and 3D communicating based on user defined context. A prototype is also developed in the VGEGIS system and the experimental results have confirmed the effectiveness and efficiency of the method. The paper will provide a contribution to flexible location-based services by innovatively considering the hierarchical knowledge of the road network system and contextual visualization needs.

Abstract

Aiming at the massive data organization and management of textures with various sizes for real-time rendering of large-scale 3D city models, this paper proposes a new method: a texture spatial index tree is built up based on the hierarchical spatial index of 3D geometries, and then the texture data is written into mapping files structure through depth-first and hierarchical iteration for the clustering of data blocks, which facilitates the flexible size-changed disk I/O operations. Experimental results prove such kind of storage is more compact and more effective than single file storage method, and enables the fast access of texture data.

Abstract

Especially for landmark buildings or in the context of cultural heritage documentation, highly detailed digital models are being created in many places. In some of these models, surfaces are represented by tiles which are individually modeled as solid shapes. In many applications, the high complexity of these models has to be reduced for more x efficient visualization and analysis. In our paper, we introduce an approach to derive versions at different scales from such a model through the generalization method of typification that works for curved underlying surfaces. Using the example of tiles placed on a curved roof – which occur, for example, very frequently in ancient Chinese architecture, the original set of tiles is replaced by fewer but bigger tiles while keeping a similar appearance. In the first step, the distribution of the central points of the tiles is approximated by a spline surface. This is necessary because curved roof surfaces cannot be approximated by planes at large scales. After that, the new set of tiles with less rows and/or columns is distributed along a spline surface generated from a morphing of the original surface towards a plane. The degree of morphing is dependent on the desired target scale. If the surface can be represented as a plane at the given resolution, the tiles may be converted to a bump map or a simple texture for visualization. In the final part, a perception-based method using CSF (contrast sensitivity function) is introduced to determine an appropriate LoD (level of detail) version of the model for a given viewing scenario (point of view and camera properties) at runtime.

Abstract

In recent years, the integration of semantics into 3D city models has become a consensus. The CityGML standard laid the foundation for the storage and application of semantics, which boosts the progress of semantic 3D city modeling. This paper reports an extended semantic model based on CityGML and its visual applications under the content of a three-dimensional GIS project of China. Firstly, concepts Room, Corridor and Stair are derived from concept Space which represents the similar concept of Room in CityGML. These concepts will benefit the application of indoor navigation. Geological model is also supported by this model, which enables the underground analysis. Secondly, a semi-automatic data integration tool is developed. The types of semantic concept are defined based on the Technical Specification for Three-Dimensional City Modeling of China which leads to an adaptive way to assign semantics into pure geometry. In order to better visualize the models enriched by semantics, two fundamental techniques, data reduction and selective representation are then introduced. It shows that semantics could not only help improve the performance of exploration tasks but also enhance the efficiency of spatial cognition. Finally, two exploration cases are presented, one is indoor navigation, the semantic model is used to extract the geometric path and a semantics enhanced navigation routine is used, which greatly enriches the connotation of ordinary navigation applications; the other is a unified profiler, in order to fill up the cross-section correctly, semantics are incorporated, which help ensure the topological and semantic consistency.

Abstract

Spatial data declustering is an important data processing method for parallel spatial database especially in shared nothing parallel architecture. Spatial data declustering can achieve parallel dataflow to exploit the I/O bandwidth of multiple parallel nodes by reading and writing them in parallel, which can improve the performance of parallel spatial database evidently. Aiming at the unique spatial objects locality, this paper presents a novel spatial data declustering method, which uses Hilbert space-filling curve to impose a linear ordering on multidimensional spatial objects, and to partition spatial objects logical segments according to this ordering to preserve spatial locality of spatial objects, and then to allocate logical segments to physical parallel nodes based on round-robin rule. Experimental results show that the proposed method can obtain well spatial data declustering results.

Abstract

针对时域、空间、专题、分辨率等多种语义相互关联所导致的遥感信息处理服务组合的准确性难题,提出了一种基于语义匹配的遥感信息处理服务组合方法,包括多层次的遥感信息处理服务语义匹配和渐进精化的服务组合,即时构建与用户需求相关的服务关系与或图,将后续服务选择范围限定在需求相关服务的范围之内,在关系与或图中进行启发式搜索,并选择语义匹配度最高的子图作为服务组合的结果。

Abstract

针对结构错综复杂的目标实时绘制中的遮挡剔除问题,提出了部件可视锥概念,用一个圆锥区域描述部件在考虑其邻近范围其他部件联合遮挡情况下的可视区域,并提出了基于部件可视锥的遮挡剔除算法,实现了实时绘制过程中可见性的快速判断,并以一个典型的虚拟建筑环境为例测试了本文方法的有效性。实验证明,利用可视锥能简化绘制过程中的可见性识别,大大提高实时绘制效率。

Abstract

提出了QoS感知的多任务服务优化组合非合作博弈模型,准确刻画了不同任务之间的竞争关系,在此基础上设计了顾及QoS的遥感信息服务优化组合反应函数,为求解遥感信息服务优化组合奠定理论基础。理论和实验分析表明,该模型有利于减少任务并发时的资源冲突,最大化所有任务的平均效用。

Abstract

The efficient display of flooding in intertidal zones is crucial to coastal applications (e.g., coastal zone management and anti-flood directing systems). This paper proposes a new algorithm to plot flooded intertidal areas. Initially, a digital tide-coordinated shoreline (DTS) is traced on the basis of creating a digital intertidal zone model (DIZM) and an instantaneous water surface model (IWSM). Then unconnected depressions are obtained depending on the type of DTS. At the same time, the algorithm detects unconnected depressions by considering the influences of the changing water level, and creates an index from different water levels to corresponding depressions. Finally, unconnected depressions are effectively handled and flooded areas are plotted correctly. Experimental results demonstrate that the proposed algorithm results in a more accurate and efficient display than with traditional algorithms.

Abstract

根据海洋大气环境的多维动态特征设计了应用于专业领域的可视化系统结构体系,阐述了系统开发的关键技术并实现了系统的开发,最后以一个实例介绍系统的具体应用。

Abstract

房产管理的产权对象在三维空间中的变化具有显著的多样性与异步性特征,已有的模型以二维地图方式表达建筑物整体的动态变化,很难准确有效地表达真三维建筑多重产权实体变更的不同步性。本文充分利用房产对象的空间层次关联性及产权单元的语义约束知识,定义了从地块到幢、层、户和权属的多层次事件概念,建立了三维房产从外至内动态表示的概念模型,为三维城市空间中建筑物的变迁以及房地产权属异动的准确表达与时空分析奠定了基础。

Abstract

针对复杂三维城市模型动态可视化中实时碰撞检测的可靠性和高性能需求,充分顾及离散检测与连续检测的特点,建立了视点运动空间的胶囊体模型,并定义了其描述参数,提出了基于该模型进行实时碰撞检测的两步检测算法。其中,预检测用来提高计算效率,而精检测则有力地保证了检测的准确性。利用典型的虚拟建筑环境进行实验,证明了该算法的有效性。

Abstract

针对遥感信息服务中用户需求语义的复杂性,数据维度语义的丰富性,传感器语义的多样性,遥感信息处理语义的错综复杂性和遥感信息传输语义的时变性,从用户语义约束、数据语义约束、处理服务功能语义约束和处理服务质量语义约束等4个不同层次,建立多层次语义约束模型。

Abstract

Data skew is one of most important reasons to deteriorate the performance of parallel spatial database. This paper studies the issues of handling data skew in shared nothing parallel spatial database system architecture. A novel data skew handling method is proposed, which fulfill spatial data distribution balancing based on the spatial proximity of data fragments. The minimum spatial proximity is used to be the principle of moving data fragments among different network parallel nodes. Our experimental results show that the proposed data skew handling method can achieve dynamic data load balancing and offer significant improvement for reducing response time of parallel spatial queries.

Abstract

Spatial data balancing distribution can evidently improve the performance of parallel spatial database in shared nothing parallel architecture. Considering spatial locality and unstructured variable length characteristics of spatial data, this paper proposes a dynamic spatial data balancing distribution method under shared nothing parallel database environment. By using Hilbert ordering code to keep spatial locality relationship between spatial objects, the presented method can fulfill spatial data static balancing distribution status, which depends on hierarchically decomposing Hilbert space-filling curve code to allocate approximately even spatial data volume to parallel nodes in distributed network. Then spatial proximity index is introduced to resolve spatial data unbalancing problem caused by spatial database dynamic updating. Through moving spatial data fragments to goal node which is the minimum spatial proximity with data moving out node, the spatial database redistributing strategy can attain dynamic data balance among all network parallel nodes. Our experimental results show that the proposed method can effectively improve parallel performance deterioration resulted from spatial data unbalancing and achieve spatial data dynamic balancing distribution in parallel spatial database.

Abstract

Recently many applications require an automatic processing of massive unstructured 3D point clouds in order to extract planar surfaces of man-made objects. While segmentation is the essential step in feature extracting process, but bad-segmentation results (i.e. under and over-segmentation) are still standing as a big obstacle to extract planar surfaces with best fit reality. In this paper, we propose an extension of "SEQ-NVRANSAC" approach to avoid the bad-segmentation problems using topology information and intuitive threshold value. First, in order to avoid the under-segmentation problem, we check each one group which resulted from original "SEQ-NV-RANSAC" approach to get all neighbours points which have Euclidean distance less than the threshold value as a one surface group. This process will be repeated until no more points can be adding to that surface group. Then a new surface group will be created to check the remaining points. Second, in order to solve the oversegmentation, we propose three checks; the similarity of normal vectors (NV), the perpendicular distance and the intersection zone using bounding box test.

Abstract

The way we interact with spatial data has been changed from 2D map to 3D Virtual Geographic Environment (VGE). Three-dimensional representations of geographic information on a computer are known as VGE, and in particular 3D city models provide an efficient way to integrate massive, heterogenous geospatial information and georeferenced information in urban areas. 3D city modeling (3DCM) is an active research and practice topic in distinct application areas. This paper introduces different modeling paradigms employed in 3D GIS, virtual environment, and AEC/FM. Up-to-date 3DCM technologies are evolving into a data integration and collaborative approach to represent the full spatial coverage of a city, to model both aboveground and underground, outdoor and indoor environments including man-made objects and natural features with 3D geometry, appearance, topology and semantics.

Abstract

Because of detailed geometrical components based description, 3D complex building contains the most elaborated perceptual and comprehensive semantic information. However, since the lack of optimal simplification method, the automatic LOD generation of such kind of model becomes a bottle neck which prohibited the high-fidelity 3D city applications. This paper proposed a perceptually guided geometrical primitive location method for the optimal simplification of 3D complex buildings. Firstly, the rendered image is snapped and a 2D discrete wavelet transform based human vision system filtering approach is adopted to extract the imperceptible details in the image, and then a kind of visual difference image is generated with sufficient perceptual information. Secondly, a ray-casting like method is proposed to precisely map the perceptual information from the image onto the geometric primitives. The statistics is carried out to determine whether a traced primitive is to be preserved or simplified. The results show that this method is able to efficiently locate the perceptible primitives and leave the imperceptible and undisplayable primitives to be further handled by simplification operations which enable a strong perceptual feature preserved simplification of 3D complex building models.

Abstract

One issue of GIS is management of huge amount of spatial data. Nowadays, acquisition capacity of 3D spatial data with various scales and resolutions is much more convenient due to new 3D acquisition technologies. It is a difficulty that how to efficiently and synthetically organize and manage large scale underground 3D spatial data with contents of continuous distribution and nonuniformity. A 3D GIS data management system framework with three layers is proposed to deal with large scale underground data integrated management. The related key issues and methods include: (1) Multi-scale underground spatial object concept model. (2) 3D spatial database model considering spatial and semantic relationship and corresponding data structure is introduced to support extendable storage environment such as file system, typical commercial database management system and cluster parallel system. (3) True 3D spatial index considering level of detail (LOD). (4) Efficient dynamic dispatch method of great amount of 3D spatial data is adopted based on 3D data content and associated information. (5) 3D spatial data engine (SDE) provides a uniform access interface for file management system, relational database management system and cluster parallel system and other applications. The 3D GIS database model focuses on the key issues of massive underground 3D spatial data provides a new way for the high performance database organization and management of true 3D geological data as well as its integration with the aboveground spatial data.

Abstract

The evaluation of urban landscape and the design of urban space are in need of a scientific visual analysis tool that can wholly include the qualitative analysis, the quantitative analysis and the orientation analysis. With the outstanding saving, management, visualization and analytical functions of 3D space information, 3DGIS can exactly provide powerful technique support for this. Based on the humanistic analysis conception, the concept of visual openness index is introduced, and some visual analysis functions are designed and implemented based on VGEGIS platform. Finally a case study for the application of visual analysis is carried out and the results show that the urban design scheme evaluation is improved distinctively.

Abstract

Depth contours on a chart are important for safe navigation. The ambiguity problem can appear when points of equal depth are joined in contouring. Unreasonable solutions may mistake a shallow area for a deep one, which could result in a potential danger for navigation. A solution is presented to solve the ambiguity problem using constrained lines formed by two shallow depths. The constrained lines are used to limit the joining of the points with equal depth. Experimental results demonstrate that the proposed solution can reduce the dangers of producing non-existent deep areas in bathymetric contouring.

From 2D to 3D road networks

Abstract

The existing road‐network models based on the 2D link‐node of roadway centrelines have inhibited lane‐oriented network flow analysis and multi‐dimensional inventory management in complicated 3D urban environments. This paper proposes a hierarchical lane‐oriented 3D road‐network model (HL‐3DRNM), with a unified modelling language (UML) diagram. HL‐3DRNM is a non‐planar topological model with the support of a 3D lane ribbon cartographic display, which is characterized by: (1) multiple topological and cartographic representations and various abstraction levels (street, road segment, carriageway and lane); and (2) referenced multi‐dimensional road information (point, line, area and volume) at lane level. HL‐3DRNM provides solid mathematical foundations for a more detailed inventory management, effective network analysis and realistic navigation in the increasingly complicated 3D urban transportation systems.

Abstract

A three-dimensional (3D) spatial index is required for real time applications of integrated organization and management in virtual geographic environments of above ground, underground, indoor and outdoor objects. Being one of the most promising methods, the R-tree spatial index has been paid increasing attention in 3D geospatial database management. Since the existing R-tree methods are usually limited by their weakness of low efficiency, due to the critical overlap of sibling nodes and the uneven size of nodes, this paper introduces the k-means clustering method and employs the 3D overlap volume, 3D coverage volume and the minimum bounding box shape value of nodes as the integrative grouping criteria. A new spatial cluster grouping algorithm and R-tree insertion algorithm is then proposed. Experimental analysis on comparative performance of spatial indexing shows that by the new method the overlap of R-tree sibling nodes is minimized drastically and a balance in the volumes of the nodes is maintained.

Comparison of extraction on a plain region. (a) Extraction result of proposed method. (b) Extraction result of method implemented in ArcGIS.

Abstract

Depression filling and direction assignment over flat areas are critical issues in hydrologic analysis. This paper proposes an efficient approach for the treatment of depressions and flat areas, based on gridded digital elevation models. Being different from the traditional raster neighborhood process which is time consuming, a hybrid method of vector and raster manipulation is designed for depression filling, followed by a neighbor-grouping scan method to assign the flow direction over flat areas. The results from intensive experiments show that there is a linear relationship between time efficiency and data volume, and the extracted hydrologic structures of flat areas are also more reasonable than those proposed by the existing methods.

Abstract

This paper describes a series of tests that measured the effects of 4 factors (accuracy, density of source data, characteristics of the terrain surface, and modeling approaches) on the accuracy of digital elevation models (DEMs). A large area covered by 2 1:10,000-scale maps was selected for testing. The terrain types ranged from flat to hilly to mountainous. Results and conclusions are provided.