1. Department of Geoinformation Science Technische Universität Berlin 2009/05/19 Introduction to CityGML Thomas H. Kolbe Alexandra Stadler Chair of Geoinformation Methodology Institute for Geodesy and Geoinformation Science Berlin University of Technology { kolbe | stadler }@igg.tu-berlin.de 19th of May, 2009 EduServ7 Pre-Course Seminar in Ås

2. 2 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Copyright notice: This is copyrighted material. It is not allowed to distribute copies or parts of these slides and the video clips without the written consent of the author. Please note, that the presentation also contains third- party copyrighted material used with permission.

3. 3 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Overview  Introduction: Urban Information Modelling  CityGML overview and status  CityGML details  Extending CityGML  Application examples  Summary

4. 4 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Urban Information Modelling

5. 5 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Applications of Virtual 3D City Models

6. 6 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 3D City Modelling … is far more than the 3D visualization of reality In fact, the geometry and its appearance are only one aspect of an entity! Key issue: Semantic Modelling

7. 7 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Prospects of Semantic 3D City Models (I) Query your 3D city model! (Possibly even without 3D visualization)  From which windows in which rooms of which buildings do I have visible coverage of a certain place, road, or monument?  What is the best position for a new transmitter station such that the propagation of the radio signal is optimal?  To what floors have all buildings in a flooded area been affected?  Where are audience halls in a specific area of the town (or on the campus) with more than 500 seats, 3D projection capabilities and less than 15min to walk from a public transport stop?  Urban Data Mining, 3D cartography

8. 8 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Example for 3D Label Placement & Symbols

9. 9 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 3D Label Placement for Augmented Reality

10. 10 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Information Hub  Ongoing virtualisation of our environment Semantic models of all relevant objects in urban space Base models include most important feature classes and attributes Objects may have several geometrical representations Spatial reference links data of different disciplines, since they refer to the same physical space  base model entities

11. 11 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Prospects of a Common Ontology  Data providers (e.g. municipalities) create 3D models with a defined information level, which they can be sure will be required or useful for a wide range of applications this in turn makes it feasible / profitable for companies to create more advanced applications that exploit semantic information  Applications can rely on a specific data quality thematic and spatial structure and (a minimal set of thematic) properties of the geo-objects

12. 12 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Information Modelling at Different Scales  Model content, structure, and employed modelling principles depend on Scale Scope (application contexts) Taken from the Homepage of the Helmholtz Research Center Karlsruhe, © Karl-Heinz-Häfele

13. © NIBS 2007 13 Scope of Real Property Industry IAI-IFC Usage Space Natural Asset Linear Structure Structure Building Facility / Built Theatre / World Sub-Systems System Level Site Real Property Asset Country State / Province County Installation / Region Node Segment Room Space System Level Sub-Systems Room Water / Sea Land / Parcel Underground Air / Space Overlay Components City CityGML

14. 14 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Overview & Status

15. 15 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Requirements for 3D City Modeling  Geometric and radiometric modeling  3D Coord. Reference Systems (3D or 2D+1D / geo. or proj.)  Topology  Semantic modeling / Object classification Distinct thematic models / feature types with thematic attributes (DTM, Buildings, Transportation, Water bodies, Vegetation, etc.) Common information model / standardized data model  Different but well-defined granularities / abstraction levels Multi-scale modeling; support for generalisation  Support for the integration of different datasets

16. 16 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Requirements for 3D City Modeling  Geometric and radiometric modeling  3D Coord. Reference Systems (3D or 2D+1D / geo. or proj.)  Topology  Semantic modeling / Object classification Distinct thematic models / feature types with thematic attributes (DTM, Buildings, Transportation, Water bodies, Vegetation, etc.) Common information model / standardized data model  Different but well-defined granularities / abstraction levels Multi-scale modeling; support for generalisation  Support for the integration of different datasets

17. 17 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 CityGML – Modelling Urban Spaces Content  Data model and exchange format for virtual 3d city models  GML 3 application schema  Modelling of all relevant parts of the virtual city according to their semantics, geometry, topology and appearance XML ALKIS ATKIS [NAS]... CityGML GML ISO 191xx

18. 18 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 CityGML Development  Developed since 2002 by the Special Interest Group 3D (NorthRhine Westphalia, Germany)  Members from >70 companies, municipalities and research institutes  Adopted as international OGC standard since 08/2008 Application backgrounds of the participants  Cadastre and Topographic Mapping  Urban Planning  Building Information Modelling, AEC/FM  Mobile Telecommunication  Environmental Simulation  Training Simulation and Car Navigation  Tourism and City Business Development  Geoinformation and Computer Science  (at its beginning) Real Estate Management Broad spectrum of different modeling requirements Good base for a multi- functional standard

19. 19 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Details

20. 20 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Modularisation CityGML consists of  a core module  several extension modules  vertical subdivision …

21. 21 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Coherence of semantics and geometry … Semantic object e.g. Building Associated geometry e.g. Solid …  Use of Boundary Representation (B-Rep) for geometry modelling  Explicit relations between semantic objects and their geometrical representations * *

22. 22 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 „Availability“ of semantics CityGML: (Up to) Complex objects with structured geometry Semantics Geometry  Geometric entities know WHAT they are  Semantic entities know WHERE they are and what their spatial extents are

23. 23 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Thematic Modelling in CityGML ExternalReference - informationSystem: anyURI - externalReference: ExternalObjectReferenceType Relief Feature loD1Geometry loD3Geometry loD2Geometry Geometry > CityModel _Vegetation > _CityObject _Site_Water Bodies _City Furniture _Transpor- tation Objects CityObject Group * * *

24. 24 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Multi-scale modelling: 5 levels of details LOD 4 – Interior model „Walkable“ architectural models LOD 3 – City / Site model Detailed architectural model LOD 2 – City / Site model Explicit roof structures LOD 1 – City / Site model „Block model“ without roof structures LOD 0 – Regional model 2.5d Digital Terrain Model

25. 25 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 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 Validity extent polygon can have holes which allow nested DTMs! coarse Grid detailed TIN

26. 26 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Digital Terrain Model: UML Diagram MassPointReliefBreaklineRelief City Object gml:TriangulatedSurface _ReliefComponent + lod: integer [1] gml: MultiPoint gml: MultiCurve gml: Polygon TIN Relief ReliefFeature + lod: integer [1] extent 1 1 1 0..1 gml:GridCoverage 1 * Raster Relief

27. 27 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Example for a Nested DTM Image: PhD work of G. Agugiaro, TU Berlin Embedding of a high resolution DTM from Archeological Excavation Hole within the validity extent polygon of the low resolution surrounding DTM

28. 28 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Example for a Nested DTM Image: PhD work of G. Agugiaro, TU Berlin Embedding of a high resolution DTM from Archeological Excavation

29. 29 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 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, construction and demolition date, roof type, address no. of storeys above / below ground, storey heights

30. 30 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Building Model in LoD1: UML Diagram loD1Solid Solid Geometry Address + zipCode: int + city: String + street: String + houseNumber: String 0..* 1 BuildingPart _AbstractBuilding + function: BuildingFunction[0..*] + yearOfConstruction:integer[0..1] + roofType: RoofType[0..1] + measuredHeigth: LengthType[0..1] + … Building 0..* 0..1 Implemented in CityGML using the xNAL standard from OASIS

31. 31 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Building Model in LoD2 loD1Solid loD2MultiSurface loD2MultiCurve Surface Geometry Line Geometry loD2MultiSurface _CityObject _BoundarySurface RoofS.WallS.GroundS. ClosureSurface loD2Solid Solid Geometry _AbstractBuilding + function: BuildingFunction[0..*] + yearOfConstruction:integer[0..1] + roofType: RoofType[0..1] + measuredHeigth: LengthType[0..1] loD2Terrain IntersectionCurve LoD1LoD2 exterior Building Installation

32. 32 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Building Model in LoD3+4 loD4Multi- surface loD4Solid interior Building Furniture interior Room LoD4 CeilingS.Interior WallS. FloorS. RoofS. WallS.GroundS. Closure Surface loD3Multi- Surface LoD3 WindowDoor Opening exterior Building Installation loD3Solid Solid Geometry _Abstract Building LoD1LoD2 _BoundarySurface Surface Geometry

33. 33 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Building in LoD4 – Interior Model Entrance door „Hallway“ „Back room“ „Living room“ Doorway (with door) Passage (w/o door) Topology implies Accessibility Graph ! Rooms Can be used e.g. for escape route planning in disaster management or for mobile robotics

34. 34 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Composition Building BuildingInstallation (Dormer) BuildingPart Building Building surface (WallSurface) 3D-Modell: Stadt Coburg

35. 35 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Coherence (I) MultiSurface („MultiPatch“) Surface GeometrySemantics  1st case: structured / unstructured geometry only, possibly along with appearance properties typical models based on 3D graphics formats like VRML, X3D, KML, U3D or legacy CAD geometry formats usable (in fact tailored) for visualizations; simple visibility computations

36. 36 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Coherence (II) MultiSurface („MultiPatch“) Surface Building GeometrySemantics  2nd case: simple object with unstructured geometry identifiable objects with a set of simple thematic properties (this is the modeling capability level of e.g. Shapefiles) typical result of (current) photogrammetrical registration systems usable für visualizations & simple thematic queries; simple visibility computations

37. 37 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Coherence (III) GeometrySemantics Composite- Solid Solid Surface Building  3rd case: simple object with structured geometry typical result of 3D modelling tools, but also from (a few) photogrammetrical registration systems

38. 38 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Coherence (IV) MultiSurface („MultiPatch“) Surface GeometrySemantics Building House Garage Stairs WallSurfaceRoofSurface  4th case: complex object with unstructured geometry Data is typically derived from Building Information Models like IFC or retrieved from Facility Management

39. 39 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Spatio-semantical Coherence (V) Composite- Solid Solid Surface Building House Garage GeometrySemantics RoofSurface  5th case: spatio-semantical coherently structured object Highest quality level; can be obtained e.g. by careful derivation from Building Information Models like IFC

40. 40 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 External references Objects may  Refer to their original data sources  Refer to other external data sources containing additional data, e.g. Building: Link to cadastre, information about owners Door: Link to facility management systems Antenna: Link to mobile communication databases

41. 41 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Appearances  Materials (similar to X3D)  Textures Standard textures (explicit texture coordinates) Aerial images (georeferenced) Projected photos  Multiple appearances (themes) per object

42. 42 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Georeferenced Textures

43. 43 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Further CityGML Concepts  Support for Topology Shared geometric primitives can be referenced using XLinks  Support for generalization of 3D data Generalized objects are linked to the original objects on the larger scale  Support for spatial homogenization / integration e.g. Terrain Intersection Curves (for integration of 3D objects with the terrain)

44. 44 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Extending CityGML

45. 45 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Application Specific Extensions to CityGML  CityGML is considered a base or core information model for virtual 3D city models  But: Specific applications need specific extra information typically in close interaction with CityGML base information  Examples Environmental simulations like noise immission mapping need information about noise absorption of surfaces Cultural heritage needs to augment objects by their heritage and history, and has to consider the development along time Utility networks need to represent pipes, pipe tunnels, connectors, transforming devices

46. 46 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Extending CityGML 1.Generic Attributes & GenericCityObjects  every CityObject can have an arbitrary number of extra attributes allows to augment objects like Buildings, Roads, etc. without the need of new application schemas  GenericCityObjects can have arbitrary geometries (and generic attributes) for every LOD  “extension during runtime“ 2.Application Domain Extensions (ADE)  extra XML schemas referring to the CityGML XML schema (defined by information communities)  extensions to be formally specified in XML schema

47. 47 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Generic Objects and Attributes  Simple to use extension mechanism  GenericCityObject is used as proxy to model and exchange features which are not provided by CityGML  Generic Attributes can be used to establish (informal) application specific property sets for feature types  Some disadvantages No further semantic structuring of generic objects and attributes Possible naming conflicts Limited number of predefined attribute types: integer, double, string, date, URI

48. 48 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Mr. Smith 3500000.0... Example for Generic Attributes

49. 49 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Application Domain Extensions (ADE)  Information Communities should be able to define extensions on their own they must be able to associate new attributes to concrete CityGML feature types formal definition of new properties / feature types in XML schema similar situation to the specification of GML application schemas  Different extensions should be usable simultaneously e.g. CityGML Building features augmented both by properties from real estate and noise pollution simulation Requires combinable application schemas

50. 50 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Example of application specific attributes Example for a CityGML Building feature with application specific extra information (qualified by extra namespaces): 1000......... 8 400000

51. 51 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Application Domain Extensions (ADE)  Well-defined mechanism to extend CityGML with application specific information Additional spatial and non-spatial properties, relations, associations, new feature types Semantic and geometric structuring follows the data needs ADE hooks allow for augmenting the predefined CityGML features No formal standardization process needed  Specification within their own XML Schema Allows for XML validation of ADE enriched documents Ensures semantic and syntactic interoperability Globally unique XML namespace prevents naming conflicts ADEs can be used simultaneously within one instance documents

52. 52 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 CityGML ADEs Application Domain Extensions (ADE) XML NoiseSimul. Disaster management ALKIS ATKIS [NAS]... CityGML GML ISO 191xx

53. 53 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 ADE implementations ADEApplication domainProposed by NoiseADENoise pollution simulationSIG 3D SubsurfaceADEUnderground features, e.g. tunnels SIG 3D CAFM-ADEComputer Aided Facility Management TU München HydroADE3D flood simulationHFT Stuttgart BridgeADE (under development) Comprehensive model for bridges SIG 3D UtilityNetworkADE (under development) Utility networks, e.g. water, electricity SIG 3D Available CityGML ADEs (excerpt)

54. 54 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Application Examples

55. 55 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 The Official 3D City Model of Berlin www.3d-stadtmodell-berlin.de 3D visualization is the result of a portraying of Berlin‘s 3D city model (modeled according to CityGML)

56. 56 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Noise immision mapping EU Directive: Minimisation of noise immissions  Calculation of noise immission maps for whole North Rhine- Westphalia  Data provision and exchange via CityGML using web services (WFS, WCS, WMS): 8.4 million 3d buildings in LOD 1 3d street network in LOD 0, with additional noise related attributes 3d rail network in LOD 0 3d noise barriers in LOD 1 Digital terrain model (10 meter resolution)

57. 57 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Noise immision mapping Noise immsion maps reported to EU (via WMS service) Noise immision simulation 3d geodata in CityGML as input for the calculation of noise immision maps

58. 58 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Homeland security Testbed OWS-4 of the Open Geospatial Consortium (OGC)  Setting: Explosion of a „dirty bomb“ in the New York harbour  Task: Support the planning committee in the construction of an emergency hospital Find the appropriate location Identify best fitting existing building (size, room layout, air conditioning for decontaminations, etc.) Thematic queries & visual inspections  Link different web services and client applications Data formats: CityGML and IFC

59. 59 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Homeland Security  CityGML building visualised using LandExplorer from outside (left) room-based representation of the security level (right)

60. 60 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 http://www.opengeospatial.org/pub/www/ows4/index.html Homeland Security

61. 61 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Coming to the end…

62. 62 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 Summary CityGML is a  Geospatial Information Model (based on ISO 191xx)  and Exchange Format for virtual 3D city and regional models (implemented as GML3 Application Schema) CityGML represents Geometry, Topology, Semantics, and Appearance  esp. semantic / structural information is needed for a range of applications  gives city model data enough space to „grow“ with respect to geometric, radiometric, and semantic contents & complexity to semantic qualification / interpretation to geometric / topological correctness

63. 63 T. H. Kolbe, A. Stadler – CityGML Tutorial Department of Geoinformation Science 2009/05/19 What is CityGML‘s Use for Research?  Base model / base ontology for geodatabase developments project specific extensions (like relations or new feature types)  Could be target model of 3D extraction methods concerning feature types, aggregation structures 5 discrete scales usable for 3D generalisation  Exchange format lossless information exchange between subsystems / GeoDB increasing number of available implementations / 3D-GeoDB  Good amounts of real testdata available Berlin, Bonn, Bochum, Hamburg, Stuttgart, Recklinghausen, … also 3 freely accessible Web Feature Services delivering CityGML

64. Department of Geoinformation Science Technische Universität Berlin 2009/05/19 Introduction to CityGML Thomas H. Kolbe Alexandra Stadler Chair of Geoinformation Methodology Institute for Geodesy and Geoinformation Science Berlin University of Technology { kolbe | stadler }@igg.tu-berlin.de 19th of May, 2009 EduServ7 Pre-Course Seminar in Ås