Making interoperability persistent: A 3D geo database based on CityGML

Transcription

1 Making interoperability persistent: A 3D geo database based on CityGML Alexandra Stadler, Claus Nagel, Gerhard König, Thomas H. Kolbe Technische Universität Berlin Chair of Geoinformation Science

2 Motivation Berlin: Management of 3D geo data Collect, compare, adapt, update, exchange Data from various sources (cadastre, planning, architecture, utility networks, etc.) Precondition: Existence of a standardised data and exchange format for 3D city models Ensures consistent and interoperable data structuring Well-known representative: CityGML 2

3 CityGML: Overview 3 Content Models all relevant parts of the virtual city according to their semantics, geometry, topology and appearance GML application schema based on XML Data model and exchange format for virtual 3d city models History Developed since 2002 by the Special Interest Group 3d (NorthRhine Westphalia, Germany) Members from >70 companies, municiplaities and research institutions lead managed by Prof. Thomas H. Kolbe (IGG TU Berlin) Dr. Gerhard Gröger (IGG Uni Bonn)

4 CityGML: On its way to become an OGC standard CityGML Kick-Off CityGML OGC Discussion Paper CityGML OGC Best Practices Paper CityGML (Proposal) OGC Request for Comments <<<<<<< Public Comment Phase >>>>>>> CityGML OGC Implementation Specification (after final OGC TC vote) 4 International standard

5 CityGML: Thematically structured into object classes <<Feature>> gml::_feature ExternalReference <<FeatureCollection>> CityModel * <<Feature>> _CityObject * - informationsystem: anyuri - externalreference: ExternalObjectReferenceType <<Feature>> _Abstract Building <<Feature>> _Transportation Object <<Feature>> ReliefFeature <<Feature>> _WaterBody <<Feature>> _Vegetation LOD 0-4 GeometryProperty <<Geometry>> gml::_geometry LOD 0-4 GeometryProperty 5

6 CityGML: Coherence of semantics and geometry Semantics based on ISO Geometry based on ISO

7 A 3D geo database for Berlin 7

8 Functionality of the 3D geo database CityGML properties additions Flexible 3D geometries (recursive) aggregation of objects Digital Terrain Models (DTM) Exchange of DTM and aerial images (WebServices) Buildings up to LOD 3 Buildings including interior structures (LOD 4) Generic (prototypical) 3D objects Complex thematic modelling Referencing of exterior data sources Appearance data Version management Import and export of CityGML files 1st project phase 2nd project phase 8

9 Development cycle CityGML Xsd Schema <xs:complextype name="citymodeltype"> <xs:complexcontent> <xs:extension... Java binding (JAXB) Creation of an import and export tool for CityGML instance documents Schema-derived classes public class CityModel { } SQL queries (Imp/Export Tool) c UML Schema Export data Import data Simplification of CityGML s data model a Schemasimplification Oracle database Database creation simplified UML Schema Mapping classes to tables Relational diagram SQL DDL statements (JDeveloper) b Derivation of the relational database schema 9

10 Simplification of CityGML s data model CityGML Xsd Schema <xs:complextype name="citymodeltype"> <xs:complexcontent> <xs:extension... Java binding (JAXB) Creation of an import and export tool for CityGML instance documents Schema derived classes public class CityModel { } SQL queries (Imp/Export Tool) c UML Schema Export data Import data Simplification of CityGML s data model a Schema simplification Oracle database Database creation Simplified UML Schema Mapping classes to tables Relational diagram SQL DDL statements (JDeveloper) b Derivation of the relational database schema 10

11 Simplification of CityGML s data model Thematic model covers a broad range of application fields Complex relations within thematic modules Comparable hierarchies on the geometry level brepmember 1..* <<Geometry>> _BRepGeometry +issolid : boolean [1] +iscomposite : boolean [1] +istriangulated : boolean [1] 0..1 <<Geometry>> BRepAggregate <<Geometry>> Polygon +geometry : Polygon [1] 11

12 Derivation of the relational database schema CityGML Xsd Schema <xs:complextype name="citymodeltype"> <xs:complexcontent> <xs:extension... Java binding (JAXB) Creation of an import and export tool for CityGML instance documents Schema derived classes public class CityModel { } SQL queries (Imp/Export Tool) c UML Schema Export data Import data Simplification of CityGML s data model a Schema simplification Oracle database Database creation Simplified UML Schema Mapping classes to tables Relational diagram SQL DDL statements (JDeveloper) b Derivation of the relational database schema 12

13 Derivation of the relational database schema brepmember 1..* <<Geometry>> _BRepGeometry +issolid : boolean [1] +iscomposite : boolean [1] +istriangulated : boolean [1] 0..1 <<Geometry>> BRepAggregate <<Geometry>> Polygon +geometry : Polygon [1] BRepGeometry BRepAggregate ID: NUMBER <<PK>><<FK>> ID: NUMBER <<PK>> IS_SOLID : BOOLEAN IS_COMPOSITE : BOOLEAN IS_TRIANGULATED : BOOLEAN Polygon ID: NUMBER <<PK>><<FK>> GEOMETRY : SDO_GEOMETRY BRepAggregate ID: NUMBER <<PK>> IS_SOLID : BOOLEAN IS_COMPOSITE : BOOLEAN IS_TRIANGULATED : BOOLEAN Polygon ID: NUMBER <<PK>> IS_SOLID : BOOLEAN IS_COMPOSITE : BOOLEAN IS_TRIANGULATED : BOOLEAN GEOMETRY : SDO_GEOMETRY BRepGeometry ID: NUMBER <<PK>> TYPE : VARCHAR2(30) IS_SOLID : BOOLEAN IS_COMPOSITE : BOOLEAN IS_TRIANGULATED : BOOLEAN GEOMETRY : SDO_GEOMETRY Mapping strategies for aggregation hierarchies 13 Realisation of geometry model

14 Creation of an import and export tool CityGML Xsd Schema <xs:complextype name="citymodeltype"> <xs:complexcontent> <xs:extension... Java binding (JAXB) Creation of an import and export tool for CityGML instance documents Schema derived classes public class CityModel { } SQL queries (Imp/Export Tool) c UML Schema Export data Import data Simplification of CityGML s data model a Schema simplification Oracle database Database creation Simplified UML Schema Mapping classes to tables Relational diagram SQL DDL statements (JDeveloper) b Derivation of the relational database schema 14

15 Creation of an import and export tool: Overview Data import CityGML input file _ Read CityGML Features CityModel citymodel1 = new CityModel () ; Database import follows instance of applied Static core of the software Xsd Schema <xs:complextype name="citymodeltype"> <xs:complexcontent> <xs:extension... Java binding Access wrapper Schema derived classes public class CityModel { } Import functionality Export functionality Oracle database follows instance of applied CityGML output file _ Write CityGML Features CityModel citymodel1 = new CityModel () ; Database export Data export 15

16 Characteristics of the import/export tool Support for CityGML files of arbitrary size (>4GB) Concurrency of data processing through multithreading High performance on standard platforms Use of universally unique identifiers (UUIDs) Filter options enable user-defined import and export GML ID, GML name Bundled import and export for data tiling (classified by IDs or Bounding Boxes) Selection of object classes Published as open source software 16

17 Concurrency of data processing Parallel non-blocking execution of multiple interacting tasks Decouple compute and I/O bound Degree of parallelisation depends on number of processing cores Attention: Context switch Thread life cycle overhead Resource thrashing Reuse threads by applying a pooled threads model Thread creation overhead is spread over many tasks Thread Pool Thread Pool Worker Worker Worker Worker Queue Queue 17

18 Data import step 1 CityGML input file _ SAX parsing Temporary Buffer Buffer Queue JAXB unmarshalling Feature creation TopLevel Feature Queue Parser Thread (1 instance) Converter Thread (limited number of instances) 18

19 Data import step 2 TopLevel Feature Queue Import filter SQL creaion Geo data SQL statement Queues commit Database update Oracle database XLink Queue Importer Thread (limited number of instances) XLinks XLink Thread (limited number of instances) commit XLink information With separate XLink storage (temporary) 19

20 Data import step 3 Oracle database XLink Resolver Queue SQL statement Queue Oracle database XLink splitting SQL creation XLinks Database update With separate XLink storage (temporary) XLink Splitter Thread (1 Instanz) XLink Resolver Thread (limited number of instances) commit with resolved XLinks 20

21 Data export step 1 _ Export filter SQL TopLevel Feature ID Queue Splitter Thread (1 instance) SQL Oracle database Database output Feature Nested feature/geometry request 21 Exporter Thread (limited number of instances)

22 Data export step 2 _ Feature JAXB marshalling Temporary Buffer Buffer Queue Write CityGML CityGML output file _ 22 Exporter Thread (limited number of instances) IO Writer Thread (1 instance)

23 Some performance measurements Import Export Dataset File size Time Features / second N of workers Versioning enabled Time Features / second N of workers 1 mio LOD1 buildings 7,5 GB 1:15h no 38min :25h no 1:57h > LOD2 buildings fully textured 163 MB + 57 MB 25 min 7 4 no 4,3min 42 4 w/o textures 6,5 163 MB 28 min 4 no 2min 91 4 >200 complex LOD3 objects 40,1MB 17s 12 4 no 3:20h 0,02 4 yes 7s

24 Future plans Matching functionality (in progress) Recognise corresponding buildings in different datasets Link geometries and exchange attribute Avoid redundant information Use the tool as backend for Web Services Broaden the applicability Replacing the graphical user interface by a Web Service interface Web Feature Services (WFS) may rely on existing import and export functionality Additional export formats KML etc. Performance optimisation 24

25 Questions? Alexandra Stadler Claus Nagel Gerhard König Thomas H. Kolbe stadler nagel igg.tu-berlin.de gerhard.koenig@tu-berlin.de Technische Universität Berlin Chair of Geoinformation Science 25

26 References 3D city database (2007), [last access: ]. Döllner J, Kolbe TH, Liecke F, Sgouros T, Teichmann K (2006) The Virtual 3D City Model of Berlin - Managing, Integrating, and Communicating Complex Urban Information, In: Proceedings of the 25th Urban Data Management Symposium UDMS, Aalborg Emgård L, Zlatanova S (2007) Implementation alternatives for an integrated 3D Information Model, In: Advances in 3D Geoinformation Systems, Springer-Verlag, pp GNU Lesser General Public License, [last access: ]. Gröger G, Kolbe TH, Czerwinski A (2007), Candidate OpenGIS Implementation Specification (City Geography Markup Language), Version 0.4.0, OGC Doc. No , Open Geospatial Consortium Snowflake Software, GO Loader product page (2008), software.co.uk/products/goloader/index.htm [last access: ]. 26