OGC CityGML 2.0标准详解

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"cityGML 标准" 是由 OpenGeospatial Consortium (OGC) 制定的一个开放标准，用于描述城市与区域的三维地理信息。该标准于2012年3月9日获得批准，并在同年4月4日发布。其外部标识符为 http://www.opengis.net/spec/citygml/2.0，项目文档参考编号为 OGC12-019，版本号为2.0.0。CityGML 是一个 OpenGIS® 编码标准，由 Gerhard Gröger、Thomas H. Kolbe、Claus Nagel 和 Karl-Heinz Häfele 等编辑完成。 CityGML 的核心目标是提供一种标准化的方式来交换和共享城市地理数据，包括建筑物、道路、绿地、水体等各种城市元素的三维模型。这个标准基于 XML 架构，允许数据在不同的软件和系统之间进行互操作。CityGML 不仅关注几何形状，还包含了关于城市对象的功能、语义和动态属性，如建筑用途、交通流量等。 CityGML 标准分为多个层次，即抽象概念模型（ACM）和应用模块（Application Domain Extensions）。ACM 提供了通用的城市对象类，如建筑物、交通网络、土地使用等。而应用模块则针对特定领域的需求，如城市设施管理、城市规划或灾害模拟，提供了扩展模型。在 CityGML 中，城市模型被组织成一系列称为“级别”（Levels of Detail, LoD）的层次。LoD1 到 LoD4 表示模型的详细程度，从简单的体积表示到包含内部结构和纹理的精细模型。这种分级方式允许根据需求和应用场景选择合适的数据复杂度。 CityGML 还支持时间相关的数据，允许描述城市对象随时间的变化，例如建筑的建设过程或城市景观的演变。此外，它还提供了对城市地理信息的附加元数据描述，帮助用户更好地理解和使用数据。通过使用 CityGML 标准，地理信息系统（GIS）和其他软件可以更有效地处理和展示城市环境的复杂性。城市规划者、建筑师、工程师以及环境科学家都能从中受益，因为数据的标准化使得跨部门的合作变得更加容易，同时也促进了公众参与和决策过程的透明度。 CityGML 标准是城市和区域三维建模的重要工具，它推动了地理空间信息的标准化，提高了数据的互操作性和重用性，对于推动智慧城市的建设和可持续发展具有重要意义。

xvi

or built structures can be represented. This coherent model structure facilitates the similar understanding of

semantic entities and helps to reduce software implementation efforts. Both the Bridge and the Tunnel model

introduce further concepts and model elements which are specific to bridges and tunnels respectively.

Additions to existing thematic modules

 CityGML Core module (cf. chapter 10.1)

Two new optional attributes have been added to the abstract base class core:_CityObject within the

CityGML Core module: relativeToTerrain and relativeToWater. These attributes denote the feature’s

location with respect to the terrain and water surface in a qualitative way, and thus facilitate simple and

efficient queries (e.g., for the number of subsurface buildings) without the need for an additional digital

terrain model or a model of the water body.

 Building module (cf. chapter 10.3)

o LOD0 representation

Buildings can now be represented in LOD0 by footprint and/or roof edge polygons. This al-

lows the easy integration of existing 2D data and of roof reconstructions from aerial and satel-

lite imagery into a 3D city model. The representations are restricted to horizontal, 3-

dimensional surfaces.

o Additional thematic boundary surfaces

In order to semantically classify parts of the outer building shell which are neither horizontal

wall surfaces nor parts of the roof, two additional boundary surfaces are introduced:

OuterFloorSurface and OuterCeilingSurface.

o Additional relations to thematic boundary surfaces

In addition to _AbstractBuilding and Room, the surface geometries of BuildingInstallation and

IntBuildingInstallation features can now be semantically classified using thematic boundary

surfaces. For example, this facilitates the semantic differentiation between roof and wall sur-

faces of dormers which are modeled as BuildingInstallation.

o Additional use of implicit geometries

Implicit geometries (cf. chapter 8.3) are now available for the representation of _Opening,

BuildingInstallation, and IntBuildingInstallation in addition to BuildingFurniture. A prototyp-

ical geometry for these city objects can thus be stored once and instantiated at different loca-

tions in the 3D city model.

 Generics module (cf. chapter 10.12)

Two generic attributes have been added to the Generics module: MeasureAttribute and

GenericAttributeSet. A MeasureAttribute facilitates the representation of measured values together with

a reference to the employed unit. A GenericAttributeSet is a named collection of arbitrary generic at-

tributes. It provides an optional codeSpace attribute to denote the authority organization who defined

the attribute set.

 LandUse module (cf. chapter 10.10)

The scope of the feature type LandUse has been broadened to comprise both areas of the earth’s surface

dedicated to a specific land use and areas of the earth’s surface having a specific land cover with or

without vegetation.

 Attributes class, function, and usage (all modules)

In order to harmonize the use of the attributes class, function, and usage, this attribute triplet has been

complemented for all feature classes that at least provided one of the attributes in CityGML 1.0.

Additions to the CityGML code list mechanism

In CityGML, code lists providing the allowed values for enumerative attributes such as class, function, and

usage can be specified outside the CityGML schema by any organization or information community according to

their specific information needs. This mechanism is, however, not fully reflected in the CityGML 1.0 encoding

schema, because in a CityGML 1.0 instance document a corresponding attribute cannot point to the dictionary

with the used code list values. This has been corrected for CityGML 2.0: All attributes taking values from code

lists are now of type gml:CodeType following the GML 3.1.1 mechanism for the encoding of code list values (cf.

OpenGIS

Encoding Standard

OGC 12-019

OGC® City Geography Markup Language (CityGML)

Encoding Standard

1 Scope

This document is an OGC Encoding Standard for the representation, storage and exchange of virtual 3D city and

landscape models. CityGML is implemented as an application schema of the Geography Markup Language

version 3.1.1 (GML3).

CityGML models both complex and georeferenced 3D vector data along with the semantics associated with the

data. In contrast to other 3D vector formats, CityGML is based on a rich, general purpose information model in

addition to geometry and appearance information. For specific domain areas, CityGML also provides an exten-

sion mechanism to enrich the data with identifiable features under preservation of semantic interoperability.

Targeted application areas explicitly include urban and landscape planning; architectural design; tourist and

leisure activities; 3D cadastres; environmental simulations; mobile telecommunications; disaster management;

homeland security; vehicle and pedestrian navigation; training simulators and mobile robotics.

CityGML is considered a source format for 3D portraying. The semantic information contained in the model can

be used in the styling process which generates computer graphics represented e.g. as KML/COLLADA or X3D

files. The appropriate OGC Portrayal Web Service for this process is the OGC Web 3D Service (W3DS). An

image-based 3D portrayal service for virtual 3D landscape and city models is provided by the OGC Web View

Service (WVS).

Features of CityGML:

 Geospatial information model (ontology) for urban landscapes based on the ISO 191xx family

 GML3 representation of 3D geometries, based on the ISO 19107 model

 Representation of object surface characteristics (e.g. textures, materials)

 Taxonomies and aggregations

o Digital Terrain Models as a combination of (including nested) triangulated irregular networks

(TINs), regular rasters, break and skeleton lines, mass points

o Sites (currently buildings, bridges, and tunnels)

o Vegetation (areas, volumes, and solitary objects with vegetation classification)

o Water bodies (volumes, surfaces)

o Transportation facilities (both graph structures and 3D surface data)

o Land use (representation of areas of the earth’s surface dedicated to a specific land use)

o City furniture

o Generic city objects and attributes

o User-definable (recursive) grouping

 Multiscale model with 5 well-defined consecutive Levels of Detail (LOD):

o LOD0 – regional, landscape

o LOD1 – city, region

o LOD2 – city districts, projects

o LOD3 – architectural models (outside), landmarks

o LOD4 – architectural models (interior)

 Multiple representations in different LODs simultaneously; generalisation relations between objects in

different LODs

 Optional topological connections between feature (sub)geometries

 Application Domain Extensions (ADE): Specific “hooks” in the CityGML schema allow to define ap-

plication specific extensions, for example for noise pollution simulation, or to augment CityGML by

properties of the new National Building Information Model Standard (NBIMS) in the U.S.

2 Conformance

Conformance targets addressed by this International standard are CityGML instance documents only. Future

revisions of this International Standard may also address consumers or producers as conformance targets.

Clauses 8 to 10 of this International standard specify separate CityGML XML Schema definitions and normative

aspects, i.e. CityGML modules, which shall be used in CityGML instance documents in accordance with clause

7. Implementations are not required to support the full range of capabilities provided by the universe of all

CityGML modules. Valid partial implementations are supported following the rules and guidelines for CityGML

profiles in chapter 7.2.

CityGML instance documents claiming conformance to this International Standard shall:

a) conform to the rules and requirements specified in clauses 7 to 10;

b) pass all relevant test cases of the abstract test suite in annex B.1;

c) satisfy all relevant conformance classes of the abstract test suite related to CityGML modules in annex

B.2.

3 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provi-

sions of this part of OGC 12-019. For dated references, subsequent amendments to, or revisions of, any of these

publications do not apply. However, parties to agreements based on this part of OGC 12-019 are encouraged to

investigate the possibility of applying the most recent editions of the normative documents indicated below. For

undated references, the latest edition of the normative document referred to applies.

The following documents are indispensable for the application of the CityGML standard. The geometry model of

GML 3.1.1 is used except for some added concepts like implicit geometries (cf. chapter 8.2). The appearance

model (cf. chapter 9) draws concepts from both X3D and COLLADA. Addresses are represented using the

OASIS extensible Address Language xAL.

ISO 8601:2004, Data elements and interchange formats – Information interchange – Representation of dates

and times

ISO/TS 19103:2005, Geographic Information – Conceptual Schema Language

ISO 19105:2000, Geographic information – Conformance and testing

ISO 19107:2003, Geographic Information – Spatial Schema

ISO 19109:2005, Geographic Information – Rules for Application Schemas

ISO 19111:2003, Geographic information – Spatial referencing by coordinates

ISO 19115:2003, Geographic Information – Metadata

ISO 19123:2005, Geographic Information – Coverages

ISO/TS 19139:2007, Geographic Information – Metadata – XML schema implementation

ISO/IEC 19775:2004, X3D Abstract Specification

OpenGIS

Abstract Specification Topic 0, Overview, OGC document 04-084

OpenGIS

Abstract Specification Topic 5, The OpenGIS Feature, OGC document 99-105r2

OpenGIS

Abstract Specification Topic 8, Relations between Features, OGC document 99-108r2

OpenGIS

Abstract Specification Topic 10, Feature Collections, OGC document 99-110

OpenGIS

Geography Markup Language Implementation Specification, Version 3.1.1, OGC document 03-105r1

OpenGIS

GML 3.1.1 Simple Dictionary Profile, Version 1.0.0, OGC document 05-099r2

IETF RFC 2045 & 2046, Multipurpose Internet Mail Extensions (MIME). (November 1996)

IETF RFC 2396, Uniform Resource Identifiers (URI): Generic Syntax. (August 1998)

W3C XLink, XML Linking Language (XLink) Version 1.0. W3C Recommendation (27 June 2001)

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