对城市地理标记语言(CityGML)的探讨

虚拟3D城市模型是三维城市GIS研究的基础。本文对CityGML1.0(City Geography Markup Language1.0,城市地理标记语言)的发展和核心技术进行了深入的研究,其主要内容包含了CityGML1.0的5层LOD模型、空间数据模型、CityGML模块、应用领域扩展等,还给出了基于CityGML1.0开发的系统实例,最后对CityGML的应用和发展进行了预测。     

Development of CityGML Application Domain Extension for Indoor Routing and Positioning

CityGML is an open data model for storage and exchange of 3D city models. It is categorised into thirteen thematic classes, i.e., buildings, tunnels, bridges, etc., lacking the other themes such as indoor routing and positioning. With the amplified use of indoor routing and positioning, the need for prerequisite notion of detailed semantic, as well as geometric information of the 3D building data has grown. We intend to extend the CityGML schema to add attributes of indoor features using the facility of Application Domain Extension (ADE) provided by the OGC CityGML 2.0. In this study, we aim to showcase the formation of Indoor Routing and Positioning ADE along with the process concerning its development, such as the 3D model design, network dataset creation, routing, positioning and Unified Modeling Language based ADE application schema generation. This research would help the users to easily store and exchange 3D city data on which they can perform routing and positioning inside the buildings with enhanced semantic and geometric properties.     

UML‐Based Approach to Developing a CityGML Application Domain Extension

Recently a national 3D standard was established in the Netherlands as a CityGML Application Domain Extension (called IMGeo). In line with the Dutch practice of modeling geo‐information, the ADE is developed using a model driven approach. The classes are designed in UML and automatically mapped to GML schema. The current OGC CityGML specification does not provide rules or guidance on correctly modeling an ADE in UML. This article fills this gap by studying how CityGML can be extended for specific applications starting from the UML diagrams. Six alternatives for modeling ADEs in UML are introduced and compared. The optimal alternative is selected and applied to obtain the national 3D standard. The approach was extensively discussed with international experts, who were members of both SIG3D and other working groups. As a consequence the approach was adopted by the SIG3D, the Special Interest Group 3D which, among other things, work on the 3D standard CityGML in cooperation with OGC. Therefore the approach contains many issues that can be generalized and reused by future domain extensions of CityGML. To further support this, the article formulates a model‐driven framework to model CityGML ADEs. Open issues are described in the conclusions.     

利用CityGML模型自动构建三维封闭建筑体

给出了利用CityGML模型自动构建三维封闭建筑体的基本框架和流程。充分利用已有的CityGML数据,分析其与三维封闭建筑体的语义关联和差别,奠定利用CityGML构建三维封闭建筑体的理论基础;从构建三维封闭建筑体所需几何数据出发,根据语义关联从CityGML中提取相应的几何数据,构建符合三维封闭建筑体要求的几何对象,满足三维立体规划和审批、核查的空间数据需要,进而弥补传统地籍数据采集方式的不足。     

CityGML goes mobile: application of large 3D CityGML models on smartphones

CityGML, a semantic information model for digital/virtual city models has become quite popular in various scenarios. While the data format is still actively under development, it is already supported by different software solutions, especially GIS-based desktop applications. Mobile systems on the other hand are still neglected, even though the georeferenced objects of CityGML have many application fields, for example, in the currently popular area of location-based Augmented Reality. In this paper we present an independent multi-platform CityGML viewer, its architecture and specific implementation techniques that we use to realize and optimize the process of visualizing CityGML data for use in Augmented Reality. The main focus lies in improving the implementation on mobile devices, such as smartphones, and assessing its usability and performance in comparison to web-based approaches. Due to the constrained hardware resources of smartphones, it is a particular challenge to handle complex 3D objects and large virtual worlds as provided by CityGML, not only in terms of memory and storage space, but also with respect to mobile processing units and display sizes.     

CityGML应用领域三维建模研究

传统三维城市建模局限于可视化和信息共享困难,OGC为此推出CityGML.本文以房产领域为例,研究基于CityCML的应用领域三维建模方法,探讨CityGML框架下的应用领域专题模型设计方法,分析三维空间对象的信息描述及可视化机制,并以一小区域数据验证了本文方法的可行性.     

Utilities of Virtual 3D City Models Based on CityGML: Various Use Cases

Virtual 3D city models are increasingly being used to model the realms of the real world for utilization in a number of applications related to environmental simulations including, urban planning, mapping the energy characteristics of buildings, noise mapping, flood modelling, etc. Apart from geometric and appearance/textural information, these applications have a requirement for complex urban semantics. Currently, a number of 3D standards are available in CAD, BIM and GIS related domains for the storage, visualization and transfer of 3D geospatial datasets. Initially, the 3D data models (such as COLLADA, VRML, X3D, etc.) were purely graphical/geometrical in nature and mainly used for visualization purposes. With the inclusion of thematic modules in OGC CityGML, the integration of geometry and semantics in a single data model paved the way for better sharing of virtual 3D city models. In spite of the availability of a wide range of 3D data standards, there are certain differences with respect to geometry, topology, semantics, LODs, etc., which complicates the integration of 3D geodata from heterogeneous sources. This paper serves to highlights the need for the innovative solutions with respect to the urban environmental related simulations primarily based on the use of virtual 3D city models. Four use cases are studied in this context namely, (1) urban solar potential estimation using CityGML models, (2) simulation of traffic noise level mapped on building walls from the urban road segments, (3) CityGML based 3D data models interoperability, and (4) 3D indoor logistics and subsurface utilities. However, for modelling majority of use cases, CityGML does not provide explicit thematic representations but provides support for extending the CityGML schema using Application Domain Extensions. In a nutshell, the study explores the semantic modelling capabilities of the CityGML for the transformation of native 3D virtual city models to one satisfying capabilities like semantic information and support towards interoperability.     

A multiple representation data structure for dynamic visualisation of generalised 3D city models

In this paper, a novel multiple representation data structure for dynamic visualisation of 3D city models, called CityTree, is proposed. To create a CityTree, the ground plans of the buildings are generated and simplified. Then, the buildings are divided into clusters by the road network and one CityTree is created for each cluster. The leaf nodes of the CityTree represent the original 3D objects of each building, and the intermediate nodes represent groups of close buildings. By utilising CityTree, it is possible to have dynamic zoom functionality in real time. The CityTree methodology is implemented in a framework where the original city model is stored in CityGML and the CityTree is stored as X3D scenes. A case study confirms the applicability of the CityTree for dynamic visualisation of 3D city models.     

基于CityGML的城市3维空间数据组织

当前的3维GIS重视3维空间方面的研究。重点是研究3维空间的几何对象的数据组织、操作方法以及查询分析等内容。本文通过对3维空间数据模型的研究,建立了一种基于CityGML语义的以建筑物为主的城市目标3维空间数据组织方法。这种方法丰富了城市3维空间数据建模,尤其对3维中的城市目标查询、统计和分析奠定了良好的基础。     

基于CityGML的城市建筑物三维建模研究

城市建筑物三维建模是虚拟3D城市建模的基础和重要组成部分。本文对基于CityGML1.0（City Geography Markup Language 1.0,城市地理标记语言）的城市建筑物三维建模技术进行了深入的研究,主要内容包含了CityGML1.0的简介、城市建筑物三维建模的方法和内容等,并给出了一个实际建模的例...     

Modelling underground cadastral survey data in CityGML

In underground environments, survey elements such as survey points and observations provide the information required to define legal boundaries. These elements are also used to connect underground legal spaces to a geodetic survey network. Due to the issues of current 2D approaches for managing underground cadastral data, prominent 3D data models have been extended to support underground land administration. However, previous studies mostly focused on defining underground legal spaces and boundaries, with less emphasis on survey elements. This research aims to extend CityGML to support underground cadastral survey data. The proposed extension is based on the survey elements elicited from underground cadastral plans, which is then implemented for an underground case study area in Melbourne, Australia. This extension integrates underground survey data with legal and physical data in a 3D digital environment and provides an improved representation of survey elements, facilitating the management and communication of underground cadastral survey data.     

A modular graph transformation rule set for IFC‐to‐CityGML conversion

Conversion of Industry Foundation Classes (IFC) building models into CityGML city models is one of the operational scenarios for BIM–GIS integration, with a variety of applications producing and consuming data on either side. Given the in‐depth cross‐domain knowledge required to specify such conversions, the heterogeneity of the IFC input data and the use cases for the resulting CityGML, flexible and configurable solutions are needed that make conversion details accessible to domain specialists. Graph transformation as a conversion method fulfils these requirements. We propose to extend the modularity given by single transformation rules at a more coarse‐grained level and identify four layers with modules of associated rules. We describe a self‐contained set of rules across these modules and demonstrate its application to a range of building models.     

Implementation of CityGML energy application domain extension (ADE) for integration of urban solar potential indicators using object-oriented modelling approach

With the advent of energy rating systems and increased energy efficiency requirements for built environment, the assessment of energy performance of new buildings and refurbishment rates of existing buildings have become an important compliance in the building design process. In order to analyse and simulate the effects of energy-efficient measures for buildings, it is essential to establish spatio-semantic information interoperability between the building design and energy modelling softwares. Data interoperability facilitates different domains to interact with the single building model. The geometrical properties of building semantics such as effective areas exposed to total incident radiation were used as indicators for assessment of seasonal solar potential of buildings. The key urban solar potential indicators were identified based on the semantic components of buildings. The CityGML instance document derived from a proposed energy application domain extension (ADE) conceptual schema could be used as common interoperable model for both the design and energy simulation systems.     

Modelling and analysing 3D buildings with a primal/dual data structure

While CityGML permits us to represent 3D city models, its use for applications where spatial analysis and/or real-time modifications are required is limited since at this moment the possibility to store topological relationships between the elements is rather limited and often not exploited. We present in this paper a new topological data structure, the dual half-edge (DHE), which permits us to represent the topology of 3D buildings (including their interiors) and of the surrounding terrain. It is based on the idea of simultaneously storing a graph in 3D space and its dual graph, and to link the two. We propose Euler-type operators for incrementally constructing 3D models (for adding individual edges, faces and volumes to the model while updating the dual structure simultaneously), and we also propose navigation operators to move from a given point to all the connected planes or polyhedra for example. The DHE also permits us to store attributes to any element. We have implemented the DHE and have tested it with different CityGML models. Our technique allows us to handle important query types, for example finding the nearest exterior exit to a given room, as in disaster management planning. As the structure is locally modifiable the model may be adapted whenever a particular pathway is no longer available. The proposed DHE structure adds significant analytic value to the increasingly popular CityGML model.     

房屋物理模型在三维地籍中的表达

公寓是地籍系统中最具代表性并应以3D形式登记的不动产单元,其建筑结构及空间形态影响着各单元在三维地籍注册中所占据的空间,将房屋几何信息引入地籍系统可实现法定空间的准确表达。本文以ISO/TC 211土地管理域模型LADM为模板,基于地籍管理中"法定空间-物理结构"理论,将房屋物理模型引入LADM,以房屋或建筑物物理实体模型或几何信息为空间参照,在三维地籍系统中实现公寓单元"法定空间"的准确表达与登记。     

Advances in techniques to formulate the watertight concept for cadastre

The world’s rising urban density expansion has resulted in a proliferation of attempts to efficiently use space and a higher level of spatial complexity in metropolitan areas. 3D geospatial data models are increasingly being embraced to facilitate communicating the spatial dimensions of complex built environments in different applications. For example, the use of 3D models in land administration systems has been recognized as a good approach for communicating the spatial complexity of legal spaces within multi‐storey buildings. The spatial extent of legal space—to which rights, restrictions and responsibilities relate in a 3D digital cadastre—needs to be accurately defined and geometrically closed; watertight. Therefore, this study aims to address the challenges regarding checking the closure of diverse 3D legal spaces and engage several techniques to formulate the watertight concept for cadastre. The research’s methodology is built on a 3D polyhedral surface using a half‐edge data structure. A primitive check is employed to assess the spatial consistency of lower‐dimensional primitives of 3D objects. Subsequently, advanced closure checks ensure the closure of volumetric legal spaces represented by 2‐manifold and non‐2‐manifold data models. The article concludes that, by adopting the proposed approaches, the internal spatial consistency of legal spaces in urban land administration will be certified.     

三维城市模型的研究现状评述

三维城市模型（简称3DCM）的研究是近年来GSI领域内的一个研究热点，在交通、地质、帮山、测绘、尤其是在规划、建设、环保等方面有着十分重要的研究意义。就3DCM的发展及其目前的研究现状，从其理论角度进行较详细的评述，指出其目前存在的问题，以供相关研究者参考。     

一种基于CityGML的三维模型单体化方法

实景三维中国建设应满足自然资源管理与社会经济发展需求,因此需要对基础地理信息产品进行实体化改造,三维模型单体化正是实体化改造的关键环节。本文提出了一种基于CityGML的三维模型单体化方法,首先根据地物实体轮廓的二维矢量面提供的顶点坐标及高程信息,构造墙面、屋顶等多边形平面组成地物的简单三维表达,然后配合渲染到纹理技术（RTT）进行纹理贴图,基于CityGML为每个二维矢量面对应的地物重构出有语义、有LOD层级的三维模型。该方法能够高效地实现三维模型单体化,且成果模型容量小,可满足各种实景三维应用需求。     

基于3ds MAX的三维数字城市可视化模型构建方法

随着地理空间信息技术发展与应用的不断进步,数字城市建设已从二维向三维发展,数字城市可视化模型的构建是数字城市的重要工作。本文分析三维数字城市的数据需求,结合3ds Max软件实现三维地形模型、三维建筑模型、三维小品模型技术,构建三维数字城市可视化综合模型。     

基于SketchUp和ArcGIS的城市3维建模技术研究

城市3维模型数据是指计算机对一个城市内所有固定对象的3维表达,是数字城市建设的一种重要框架数据。ESRI公司的ArcGIS系列软件作为一款功能强大的GIS软件,虽然在ArcGIS 9.2版本中对ArcGIS 3D分析扩展（包括ArcScene和ArcGlobe应用）的很多功能上进行了显著的改进,但是在制作3维对像数据上还是存在不足,需要借助其他专业软件辅助创建3维对象。而与专业3维模型软件之间的结合使用,例如,Google SketchUp,将为3维数据的实时和交互分析提供更多选择和机会。