CityGML Background and Design

Transcription

1 Institut für Kartographie und Geoinformation, Uni Bonn Lehrstuhl für Geoinformation CityGML Background and Design Dr. Thomas H. Kolbe OWS-4 Kickoff Meeting June 14, 2006 Institut für Kartographie und Geoinformation, Uni Bonn Lehrstuhl für Geoinformation, Prof. Dr. Lutz Plümer

2 Virtual 3D City Models SI, Universität Stuttgart Fa. Conterra IKG, Universität Bonn T-Mobile Rheinmetall Defence Electronics Sony Corporation Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 2

3 Stages of Information Integration System A Web Client C System B graphical Elements VRML / X3D / KML Visualization level OGC Web 3D Service, WTS graphical Elements Geodata CityGML Geodata level OGC Web Feature Service Geodata Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 3

4 Goals of CityGML (I) Establish high degree of semantic (and syntactic) interoperability enabling multifunctional usage of 3D city models definition of a common information model 3D geo base data (in the tradition of most European 2D digital landscape models, cadastre models) Representation of 3D topography as observed explicit 3D shapes; mainly surfaces & volumes identification of most relevant feature types usable in a wide variety of applications limited inclusion of functional aspects in base model Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 4

5 Goals of CityGML (II) Suitability for Spatial Data Infrastructures mapping to appropriate exchange format -> GML3 needs high degree of expressivity wrt. OO models must be usable in the context of OGC Web Services possibility to link any CityGML feature to more specialised, functional models / external data sources Must be simple to use for applications well-defined semantics for feature types; however semantic structure not too fine-grained subset of GML3 geometries (no curved lines, surfaces) Boundary representation with absolute coordinates advantage: directly manageable within 3D GIS / geo DB Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 5

6 Originator: GDI NRW and the SIG 3D Geodata Infrastructure North Rhine-Westphalia PPP founded in 1999 by the state government more than 100 institutions organized in 6 Special Interest Groups very active in OGC (GML3, WPOS, Gazetteer, Metadata) Special Interest Group 3D (SIG 3D) open group with >70 active members; 3 working groups from industry, government, municipalities and academia participants from all over Germany, Austria, Switzerland, and UK aims: interoperable visualization Web 3D Service and exchange of 3D geodata CityGML Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 6

7 SIG 3D members (excerpt) Municipalities Berlin Hamburg Köln Düsseldorf Bremen Essen Wuppertal Bochum Stuttgart Administration State mapping agencies (DE) Ordn.Survey UK Companies T-Mobile Bayer Industry Services Rheinmetall Defence 3D Geo CPA Geoinformation Con Terra GIStec GTA Geoinformatik Inpho Citygrid (AT) CyberCity (CH) Snowflake (UK) Science Univ. of Bonn Univ. of Hamburg Univ. of Potsdam Univ. of Hannover Univ. of Dortmund Univ. of Münster Fraunhofer Institute for Computer Graphics, Darmstadt Helmholtz Research Center Karlsruhe Univ. of Applied Sciences Stuttgart Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 7

8 Design Principles (I) Representation of the 4 most important aspects of virtual 3D city models wrt. multifunctional usage: Geometry Topology Semantics Appearance Usage of topology, appearance should be optional Semantics restricted to general classifications limited inclusion of functional aspects further functional aspects should be covered by application specific extensions to CityGML Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 8

9 Design Principles (II) Adaptibility to different information communities values of enumerative attributes are represented in external codelists (increase of semantic & syntactic interoperability) communities may redefine the codelists without changing the CityGML schema / data model Coherent spatial / semantic modeling Features are decomposed both wrt. their spatial and semantic properties Balance between simplicity and need for structure Multiscale model Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 9

10 Multi-scale modelling: 5 level of details LOD 0 Regional model 2.5D Digital Terrain Model LOD 1 City / Site model block model w/o roof structures LOD 2 City / Site model textured, differenciated roof structures LOD 3 City / Site model detailed architecture model LOD 4 Interior model walkable architecture models Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 10

11 Coherent spatial / semantic aggregation 3D-Model: City of Coburg Building installation (dormer) Building part Building Building part Building Wall surface (exterior) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 11

12 CityGML Dataset in Level of Detail 3 3D-Model: Dr. Benner, Forschungszentrum Karlsruhe Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 12

13 External references Telecomm. DB Cadastral DB Facility Management System Every object (part) may have references to corresponding objects in external databases Connection with external information, e.g.: building: link to cadastre, owner's contact information door, antenna: link to facility management systems Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 13

14 Terrain Intersection Curve (TIC) Interface between 3D objects and the terrain ensure matching of object textures with the DTM DTM may be locally warped to fit the TIC Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 14

15 Closure Surfaces Seal open 3D objects in order to be able to compute their volumes Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 15

16 Thematic Schema: UML Diagram <<FeatureCollection>> CityModel <<Feature>> _CityObject ExternalReference - informationsystem: anyuri - externalreference: ExternalObjectReferenceType _Transportation Objects _City Furniture CityObject Group _Water Bodies _Site Complex Relief lod1geometryproperty lod2geometryproperty Geometry _Vegetation lod3geometryproperty Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 16

17 Digital Terrain Models DTM for each Level of Detail can be composed of TINs (Triangulated Irregular Network), Grids, 3D Breaklines, and 3D Mass Points Each DTM component may be restricted to be valid in a specific region by providing a validity extent polygon detailed TIN coarse Grid Validity extent polygon can have holes which allow nested DTMs! Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 17

18 Building Model Coherent aggregation of spatial and semantical components (recursive) composition of building parts thematic surfaces (roof surface, wall surface, etc.) [from LOD2] building installations like dormers, stairs, balconies [from LOD2] openings like doors and windows [from LOD3] rooms and furniture [in LOD4] Components contain relevant thematic attributes name, class, function, usage, (constr. date, roof type, address) no. of storeys above / below ground, storey heights Surface appearance characteristics (textures, colours) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 18

19 Room Building in LoD4 Interior Model Topology implies an Accessibility Graph Back room Passage (w/o door) Living room Entrance door Hallway Doorway (with door) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 19

20 Deriving LOD4 models from IFC IFC Model Current research of Benner, Geiger, Leinemann Helmholtz Research Center Karlsruhe Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 20

21 Deriving LOD4 models from IFC IFC Model Derived CityGML object Current research of Benner, Geiger, Leinemann Helmholtz Research Center Karlsruhe Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 21

22 Generic CityObjects and Attributes Explicitly modeled feature types have the advantage of well-defined object semantics However, often concrete models comprise additional attributes or features not covered by the model Incorporation of generic CityObjects and attributes every CityObject can have an arbitrary number of generic attributes (string, int, real, date, URI) GenericCityObject is subclass of CityObject arbitrary GML3 geometry for each LOD may only be used, if there is no appropriate concept provided by CityGML (problematic wrt. semantic inter.) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 22

23 Grouping of CityObjects Feature type CityObjectGroup has arbitrary CityObjects as members CityObjectGroup is a CityObject can become again member of another group every member can denote its role in a group usable for user-defined aggregations e.g. results of classifications or selection usable also to group CityObjects wrt. some function or area, e.g. city districts, building storeys, or evacuation areas Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 23

24 Backdoor Topology How to allow for flexible usage of topology? Until now, most 3D city models do consider topology need to represent city models with geometry only Topology model of GML3 sophisticated, but complex would make it necessary to implement 2 options for the representation of spatial properties Approach in CityGML: topological connections are represented by Xlinks GML3 geometries are objects; composites/aggregates can include subgeometries by value or by reference; references express topological relations Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 24

25 Geometric-topological Composition recursive aggregation arbitrary depth Wall face will be partitioned into 2 faces Solid Geometry Solid Solid Aggregate explicit topol. connection - but: goes beyond B-Rep S.1 S.2 Solid aggregate Solid 1 Solid 2? Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 25

26 Semantic Relations by Topology Multiple referencing of geometry (components) realizes topological, but also semantic relations redundancy free description of space and surfaces possible, thus no overlaps occur Rheinmetall Defence Electronics This surface is part of the geometries of the bridge object and the road object Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 26

27 Extensions to GML3 Surface Materials Colors, Textures (adopted from X3D) TexturedSurface is subclass of gml:orientablesurface Implicit geometries (Prototypic shapes) Shape of a 3D object in local coordinates Instancing at anchor points (+ further transformations) Both are concepts used in scene graphs directly transformable to VRML, X3D, U3D etc. however only simple & limited extensions tailored to the demand of 3D city models easy to support by exporting / importing applications Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 27

28 Prototypic 3D Objects 3D city models often contain large numbers of geoobjects of identical shape but at different locations Examples: trees, traffic lights, street lamps, benches, etc. in GML3, all geometries have absolute coordinates every copy /instance would have to be explicitly represented CityGML: Implicit Geometries Separation of shape definition and georeferencing (anchor point + transform.) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 28

29 CityGML (Partial) Implementations LandXPlorer (3dgeo) CityServer 3D (GIStec / FhG IGD) SupportGIS (CPA Geo-Information) Tridicon (GTA Geoinformatik) GoPublisher (Snowflake Software UK) Aristoteles GML3 3D Viewer (IKG Uni Bonn) Open Source Framework Deegree, WFS (lat/lon, in preparation) 3D Geo DB of the cities Berlin & Bonn; Oracle Spatial and PostGIS (IKG Uni Bonn, in prep.) Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 29

30 Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 30

31 The Official 3D City Model of Berlin Background: Need for 3D city model for urban planning, city marketing, and recruiting of new enterprises Integration of existing 3D models of the departments of business development and town planning Contribution to the SDI Berlin in the field of 3D European EFRE Pilot Project from 2003 to 2005 Currently introduction into regular operation Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 31

32 Realization with interoperable Services 3D Geo Database SDI Berlin / Internet 3D City Model DTM Orthophotos Version and History Management Web Coverage Service Web Feature Service CityGML Web Terrain Service Presentation System CityGML 3D City Model Editor Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 32

33 Issues & Items for Discussion Generation of CityGML data few applications available up to now depends on source data: Is it already 3D? (Buildings, DTM) Are the data entities aggregated to identifiable objects? Are linear features like streets and rivers represented as surfaces or by center lines? Source data formats (Shape 3D, IFC possible)? Complexity of CityGML wrt. to current (3D) GIS multiple geometries per object; topology; multiple referencing of geometries; LOD model Integration / Coupling / Relation with IFC Dr. Thomas H. Kolbe - CityGML - Standard für 3D-Stadtmodelle 33