倾斜影像的三维纹理快速重建

针对三维城市模型重建,提出了一种利用倾斜影像实现城市模型纹理快速重建的方法。该方法基于摄影测量计算机视觉理论,在事先处理得到城市建筑物数字表面模型的基础上,利用共线方程计算物方与像方的几何投影关系,获得建筑物的三维信息与纹理信息。通过一定的最优算法选择出地物面的理想纹理,实现城市建筑物纹理的自动提取及稠密建筑物纹理的遮挡处理。真实影像纹理重建的结果表明:应用本文方法进行三维城市模型纹理重建具有自动化程度高、效果逼真、成本低的特点,为快速、大面积的城市真三维模型纹理重建提供了一种有效的实现途径。     

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.     

A generative statistical approach to automatic 3D building roof reconstruction from laser scanning data

This paper presents a generative statistical approach to automatic 3D building roof reconstruction from airborne laser scanning point clouds. In previous works, bottom-up methods, e.g., points clustering, plane detection, and contour extraction, are widely used. Due to the data artefacts caused by tree clutter, reflection from windows, water features, etc., the bottom-up reconstruction in urban areas may suffer from a number of incomplete or irregular roof parts. Manually given geometric constraints are usually needed to ensure plausible results. In this work we propose an automatic process with emphasis on top-down approaches. The input point cloud is firstly pre-segmented into subzones containing a limited number of buildings to reduce the computational complexity for large urban scenes. For the building extraction and reconstruction in the subzones we propose a pure top-down statistical scheme, in which the bottom-up efforts or additional data like building footprints are no more required. Based on a predefined primitive library we conduct a generative modeling to reconstruct roof models that fit the data. Primitives are assembled into an entire roof with given rules of combination and merging. Overlaps of primitives are allowed in the assembly. The selection of roof primitives, as well as the sampling of their parameters, is driven by a variant of Markov Chain Monte Carlo technique with specified jump mechanism. Experiments are performed on data-sets of different building types (from simple houses, high-rise buildings to combined building groups) and resolutions. The results show robustness despite the data artefacts mentioned above and plausibility in reconstruction.     

Earth observation data based rapid flood-extent modelling for tsunami-devastated coastal areas

Earth observation (EO)-based mapping and analysis of natural hazards plays a critical role in various aspects of post-disaster aid management. Spatial very high-resolution Earth observation data provide important information for managing post-tsunami activities on devastated land and monitoring re-cultivation and reconstruction. The automatic and fast use of high-resolution EO data for rapid mapping is, however, complicated by high spectral variability in densely populated urban areas and unpredictable textural and spectral land-surface changes. The present paper presents the results of the SENDAI project, which developed an automatic post-tsunami flood-extent modelling concept using RapidEye multispectral satellite data and ASTER Global Digital Elevation Model Version 2 (GDEM V2) data of the eastern coast of Japan (captured after the Tohoku earthquake). In this paper, the authors developed both a bathtub-modelling approach and a cost-distance approach, and integrated the roughness parameters of different land-use types to increase the accuracy of flood-extent modelling. Overall, the accuracy of the developed models reached 87–92%, depending on the analysed test site. The flood-modelling approach was explained and results were compared with published approaches. We came to the conclusion that the cost-factor-based approach reaches accuracy comparable to published results from hydrological modelling. However the proposed cost-factor approach is based on a much simpler dataset, which is available globally.     

Results of the ISPRS benchmark on urban object detection and 3D building reconstruction

For more than two decades, many efforts have been made to develop methods for extracting urban objects from data acquired by airborne sensors. In order to make the results of such algorithms more comparable, benchmarking data sets are of paramount importance. Such a data set, consisting of airborne image and laserscanner data, has been made available to the scientific community by ISPRS WGIII/4. Researchers were encouraged to submit their results of urban object detection and 3D building reconstruction, which were evaluated based on reference data. This paper presents the outcomes of the evaluation for building detection, tree detection, and 3D building reconstruction. The results achieved by different methods are compared and analysed to identify promising strategies for automatic urban object extraction from current airborne sensor data, but also common problems of state-of-the-art methods.     

The visualization of socio-economic GIS data using virtual reality tools

This paper addresses two issues: the use of 'realistic' environments for the visualization of socio-economic data, and the use of virtual reality tools for the exploration of data from existing GIS databases. 'Realistic' is here used in a narrow sense to imply the reconstruction of real-world scenes in which major components of the physical environment are reconstructed to facilitate geographical visualization. A review of visualization techniques for geographically-referenced 3-D data is presented, and the translation of an existing urban GIS database into virtual reality modelling language (VRML) demonstrated for a study area in Cardiff, UK. This work shows that the export of conventional 2-D GIS data into virtual reality toolkits can be relatively straightforward, and offers exciting new avenues for visualization and exploration. We argue that some of the parameters of the true scene such as colour, building shape, and texture may be directly modified in order to represent otherwise unobservable socio-economic characteristics, in the spirit of exploratory data analysis. These issues are of particular importance in the context of current advances towards the dynamic linkage of GIS and virtual reality modelling.     

基于高分辨率影像的城市三维建模

介绍了利用倾斜摄影影像和垂直摄影影像相结合的三维城市重建方法，分析了利用有理多项式(RPC)恢复IKONOS立体影像的模型，在VirtuoZo上实现了基于有理多项式(RPC)恢复IKONOS立体影像的模型方法，并利用其快速影像匹配技术，实现了数字地面模型DEM和正射影像，实现了手动和半自动人工地物的采集，如房屋等三维几何坐标和结构的采集；自动获取了基于不同传感器所获得影像的建筑物表面纹理，从而实现了基于多种影像快速三雏城市建模。     

一种建筑信息模型与三维数字城市集成方法

BIM的发展为数字城市三维模型提供了更加精确的数据来源,现有研究主要关注BIM空间实体模型向三维表面模型转换,缺少建筑语义信息映射及整体集成方案研究。本文以构成建筑骨架的主要空间构件为研究对象,在参考IFC标准基础上,结合数字城市应用特点设计了具有空间语义一致性的建筑构件信息模型BCM,在此基础上提出建筑信息模型和三维数字城市集成方案。首先,基于CAD图纸开展BIM模型交互式构建,然后,通过空间和语义信息映射将其转换为BCM,并基于ArcGIS Geodatabase建立建筑构件信息库,在三维数字城市场景开展建筑构件信息的集成应用。该方案可实现建筑构件信息与三维数字城市的大规模集成,对推动数字城市向智慧城市发展,进一步开展建筑内外模型集成展示、建筑节能分析、内部设施管理等具有重要价值。     

基于激光扫描技术的建筑物三维重建

三维激光扫描技术作为一种新型高精度的全自动立体扫描技术,区别于传统的单点式测量,它能够快速获取被测物体表面大量的三维空间坐标。同时获得的点云数据不仅能够直观地表现出物体属性,还能构造出目标物的三维模型进行规划分析,大大推动了数字城市的建设进程。而本文详细介绍了三维激光扫描技术,并结合实际案例来阐述利用地面激光扫描仪对青岛市某高层建筑进行外业测量以及点云数据处理,最终利用Realworks和Sketchup软件对点云数据进行三维重建及展示。     

多尺度矢量地图数据关联自动更新研究

多级比例尺矢量地图数据库一旦建成以后,数字制图的核心就从数据生产转为数据更新.小比例尺矢量地图数据库建库时必须依靠大量人机交互从大比例尺数据派生,但更新时再采取各比例尺分别独立更新的策略显然就不合时宜,既消耗大量人力和财力,又不能保证不同尺度数据之间的一致性.提出一种多尺度矢量地图数据关联自动更新方法,对于已经建成的多...     

Options for monitoring and estimating historical carbon emissions from forest degradation in the context of REDD+

Measuring forest degradation and related forest carbon stock changes is more challenging than measuring deforestation since degradation implies changes in the structure of the forest and does not entail a change in land use, making it less easily detectable through remote sensing. Although we anticipate the use of the IPCC guidance under the United Framework Convention on Climate Change (UNFCCC), there is no one single method for monitoring forest degradation for the case of REDD+ policy. In this review paper we highlight that the choice depends upon a number of factors including the type of degradation, available historical data, capacities and resources, and the potentials and limitations of various measurement and monitoring approaches. Current degradation rates can be measured through field data (i.e. multi-date national forest inventories and permanent sample plot data, commercial forestry data sets, proxy data from domestic markets) and/or remote sensing data (i.e. direct mapping of canopy and forest structural changes or indirect mapping through modelling approaches), with the combination of techniques providing the best options. Developing countries frequently lack consistent historical field data for assessing past forest degradation, and so must rely more on remote sensing approaches mixed with current field assessments of carbon stock changes. Historical degradation estimates will have larger uncertainties as it will be difficult to determine their accuracy. However improving monitoring capacities for systematic forest degradation estimates today will help reduce uncertainties even for historical estimates.     

基于局部约束的建筑物屋顶点云平面分割方法

建筑物屋顶面点云分割结果的好坏对建筑物三维模型重建起着重要的作用。针对传统RANSAC算法建筑物屋顶面点云的分割问题,提出了一种基于局部约束的建筑物点云平面分割方法。利用点云局部曲面法向约束构建法向准则,利用半径约束的点云空间聚类的方法对共面屋顶面点云进行分解,从而抑制"伪屋顶面"的产生;利用局部抽样策略降低算法的迭代次数,减少运算量。实验表明该方法能够获得稳定可靠的建筑物屋顶点云分割结果,将有利于后续的建筑物三维模型重建。     

地籍变更空间要素自动重构研究

地籍更新是现代地籍的生命所在。宗地拓扑关系的影响,使目前地籍数据库的人工交互更新方式存在编辑时间长、劳动强度大、易产生错误、难以保证空间数据一致性等问题。鉴于此,本文研究了地籍空间要素自动重构的理论和方法,包括拓扑关系判断、拓扑构建、地籍要素变化类型判断和地籍空间要素自动重构。以实际空间数据为例对所提方法进行了实验,验证了地籍空间要素自动重构的合理性与可行性。     

顾及地面POS信息的空地一体城市三维实景重建

实景三维模型为数字孪生提供了统一的数字空间底座。在城市场景中,贴近地面及在空中视角下被遮挡的地物是实景三维重建的难点。针对城市复杂空间环境和无人机飞行局限的问题,本文基于倾斜摄影与空地一体融合建模的基础理论,考虑POS信息对空地一体空三融合的影响,提出了一种顾及地面POS信息的城市实景三维重建方法,并使用此方法对佛山市历史文化街区进行了精细化建模。试验表明,与常规方法相比,该方法的模型效果好、效率高,对实景三维产品的生产与空间数据多尺度表达具有重要意义,可为数字孪生应用提供更精细的地理场景表现形式。     

Combining microsimulation and spatial interaction models for retail location analysis

Although the disaggregation of consumers is crucial in understanding the fragmented markets that are dominant in many developed countries, it is not always straightforward to carry out such disaggregation within conventional retail modelling frameworks due to the limitations of data. In particular, consumer grouping based on sampled data is not assured to link with the other statistics that are vital in estimating sampling biases and missing variables in the sampling survey. To overcome this difficulty, we propose a useful combination of spatial interaction modelling and microsimulation approaches for the reliable estimation of retail interactions based on a sample survey of consumer behaviour being linked with other areal statistics. We demonstrate this approach by building an operational retail interaction model to estimate expenditure flows from households to retail stores in a local city in Japan, Kusatsu City.      

数码城市:概念、技术支撑和典型应用

首次系统全面地介绍了有关数码城市 (CyberCity)的概念、技术支撑和典型应用 ,并结合CCGIS软件的研究开发及其在深圳和上海两个城市的示范应用 ,讨论了建设数码城市所面临的若干关键技术问题     

3D Building Modelling with Digital Map, Lidar Data and Video Image Sequences

Three-dimensional (3D) reconstruction and texture mapping of buildings or other man-made objects are key aspects for 3D city landscapes. An effective coarse-to-fine approach for 3D building model generation and texture mapping based on digital photogrammetric techniques is proposed. Three video image sequences, two oblique views of building walls and one vertical view of building roofs, acquired by a digital video camera mounted on a helicopter, are used as input images. Lidar data and a coarse two-dimensional (2D) digital vector map used for car navigation are also used as information sources. Automatic aerial triangulation (AAT) suitable for a high overlap image sequence is used to give initial values of camera parameters of each image. To obtain accurate image lines, the correspondence between outlines of the building and their line features in the image sequences is determined with a coarse-to-fine strategy. A hybrid point/line bundle adjustment is used to ensure the stability and accuracy of reconstruction. Reconstructed buildings with fine textures superimposed on a digital elevation model (DEM) and ortho-image are realistically visualised. Experimental results show that the proposed approach of 3D city model generation has a promising future in many applications.     

Identification and Modelling of Translational and Axial Symmetries and their Hierarchical Structures in Building Footprints by Formal Grammars

Buildings and other man‐made objects, for many reasons such as economical or aesthetic, are often characterized by their symmetry. The latter predominates in the design of building footprints and building parts such as façades. Thus the identification and modeling of this valuable information facilitates the reconstruction of these buildings and their parts. This article presents a novel approach for the automatic identification and modelling of symmetries and their hierarchical structures in building footprints, providing an important prior for façade and roof reconstruction. The uncertainty of symmetries is explicitly addressed using supervised machine learning methods, in particular Support Vector Machines (SVMs). Unlike classical statistical methods, for SVMs assumptions on the a priori distribution of the data are not required. Both axial and translational symmetries are detected. The quality of the identified major and minor symmetry axes is assessed by a least squares based adjustment. Context‐free formal grammar rules are used to model the hierarchical and repetitive structure of the underlying footprints. We present an algorithm which derives grammar rules based on the previously acquired symmetry information and using lexical analysis describing regular patterns and palindrome‐like structures. This offers insights into the latent structures of building footprints and therefore describes the associated façade in a relational and compact way.