department of geoinformation science technische universität berlin 2009/05/19 introduction to...

Department of Geoinformation Science

Technische Universität Berlin

2009/05/19

Introduction to CityGML

Thomas H. KolbeAlexandra Stadler

Chair of Geoinformation MethodologyInstitute for Geodesy and Geoinformation ScienceBerlin University of Technology

{ kolbe | stadler }@igg.tu-berlin.de

19th of May, 2009

EduServ7 Pre-Course Seminar in Ås

2009/05/192 T. H. Kolbe, A. Stadler – CityGML Tutorial


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Please note, that the presentation also contains third-party copyrighted material used with permission.



Overview

Introduction: Urban Information Modelling

CityGML overview and status

CityGML details

Extending CityGML

Application examples

Summary



Urban InformationModelling



Applications of Virtual 3D City Models



3D City Modelling

… is far more thanthe 3D visualizationof reality

In fact, the geometryand its appearanceare only one aspectof an entity!

Key issue: Semantic Modelling



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



Example for 3D Label Placement & Symbols



3D Label Placement for Augmented Reality



Information Hub

Ongoing virtualisationof 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



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



Information Modelling at Different Scales

Model content, structure, and employed modelling principles depend on

ScaleScope (application contexts)

Taken from the Homepage of the Helmholtz Research Center Karlsruhe, © Karl-Heinz-Häfele

13

© NIBS 2007

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Scope of Real Property Industry Scope of Real Property Industry IA

I-IFC

Usage

Space

Natural Asset

Linear Structure

Structure

Building

Facility / Built

Theatre / World

Sub-SystemsSystem

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

Overlay

Components

Components

City

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

CityG

ML



Overview & Status



Requirements for 3D City Modeling

Geometric and radiometric modeling

3D Coord. Reference Systems (3D or 2D+1D / geo. or proj.)

Topology

Semantic modeling / Object classificationDistinct 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 levelsMulti-scale modeling; support for generalisation

Support for the integration of different datasets



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

191

xx



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 differentmodeling

requirements

Good basefor a multi-

functionalstandard



Details



Modularisation

CityGML consists of a core module several extension modules vertical subdivision

CityGML Core

GML 3.1.1

Bui

ldin

g

City

Fur

nitu

re

City

Obj

ectG

roup

Land

Use

Rel

ief

Tra

nspo

rtat

ion

Veg

etat

ion

Wat

erB

ody

Appearance

Generics

…



Coherence of semantics and geometry

…

Semantic objecte.g. Building

Associated geometrye.g. Solid

…

Use of Boundary Representation (B-Rep) for geometry modelling

Explicit relations between semantic objects and their geometrical representations

* *



„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



Thematic Modelling in CityGML

ExternalReference - informationSystem: anyURI - externalReference: ExternalObjectReferenceType

ReliefFeature loD1Geometry

loD3Geometry

loD2GeometryGeometry

<<FeatureCollection>>

CityModel

_Vegetation

<<Feature>>

_CityObject

_Site_Water Bodies

_City Furniture

_Transpor-tation

Objects

CityObjectGroup

***



Multi-scale modelling: 5 levels of details

LOD 4 – Interior model„Walkable“ architectural models

LOD 3 – City / Site modelDetailed architectural model

LOD 2 – City / Site modelExplicit roof structures

LOD 1 – City / Site model„Block model“ without roof structures

LOD 0 – Regional model2.5d Digital Terrain Model



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 extentpolygon can have holeswhich allownested DTMs!

coarseGrid

detailedTIN



Digital Terrain Model: UML Diagram

MassPointReliefBreaklineRelief

CityObject

gml:TriangulatedSurface

_ReliefComponent+ lod: integer [1]

gml:MultiPoint

gml:MultiCurve

gml:Polygon

TINRelief

ReliefFeature+ lod: integer [1]

extent

1

1 10..1

gml:GridCoverage

1

*

RasterRelief



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

Hole within the validity extent polygon of the low

resolution surrounding DTM



Example for a Nested DTM

Image: PhD work of G. Agugiaro, TU Berlin

Embedding of a high resolution DTM from Archeological Excavation



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 attributesname, class, function, usage, construction and demolition date,

roof type, addressno. of storeys above / below ground, storey heights



Building Model in LoD1: UML Diagram

loD1SolidSolid

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

Implemented in CityGML using the xNAL standard from OASIS



Building Model in LoD2

loD1Solid

loD2MultiSurface

loD2MultiCurve

SurfaceGeometry

LineGeometry

loD2MultiSurface

_CityObject

_BoundarySurface

RoofS. WallS. GroundS. ClosureSurface

loD2SolidSolid

Geometry_AbstractBuilding

+ function: BuildingFunction[0..*]+ yearOfConstruction:integer[0..1]+ roofType: RoofType[0..1]+ measuredHeigth: LengthType[0..1]

loD2TerrainIntersectionCurve

LoD1 LoD2

exterior

BuildingInstallation



Building Model in LoD3+4

loD4Multi-surface

loD4Solid

loD4Solid

interiorBuildingFurniture

interiorinterior

Room

LoD4

CeilingS. InteriorWallS.

FloorS. RoofS. WallS. GroundS. ClosureSurface

loD3Multi-Surface

LoD3

Window Door

Opening

exteriorBuildingInstallation

loD3Solid

SolidGeometry

_AbstractBuilding

LoD1 LoD2

_BoundarySurfaceSurface

Geometry



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



Spatio-semantical Composition

Building

BuildingInstallation (Dormer)

BuildingPart

BuildingPart

Building

Building surface (WallSurface)

3D-Modell: Stadt Coburg



Spatio-semantical Coherence (I)

MultiSurface(„MultiPatch“)

SurfaceSurface

Geometry Semantics

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



Spatio-semantical Coherence (II)


SurfaceSurface

Building

Geometry Semantics

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 systemsusable für visualizations & simple thematic queries; simple visibility

computations



Spatio-semantical Coherence (III)

Geometry Semantics

Composite-Solid

Solid Solid

Surface Surface

Building

3rd case: simple object with structured geometry typical result of 3D modelling tools, but also from (a few)

photogrammetrical registration systems



Spatio-semantical Coherence (IV)


SurfaceSurface

Geometry Semantics

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



Spatio-semantical Coherence (V)

Composite-Solid

Solid Solid

Surface Surface

Building

House Garage

Geometry Semantics

RoofSurface

5th case: spatio-semantical coherently structured objectHighest quality level; can be obtained e.g. by careful derivation

from Building Information Models like IFC



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 ownersDoor: Link to facility management systemsAntenna: Link to mobile communication databases



Appearances

Materials (similar to X3D) Textures

Standard textures (explicit texture coordinates)

Aerial images (georeferenced)

Projected photos

Multiple appearances (themes) per object



Georeferenced Textures



Further CityGML Concepts

Support for TopologyShared geometric primitives can be referenced using XLinks

Support for generalization of 3D dataGeneralized objects are linked to the original objects on the

larger scale

Support for spatial homogenization / integratione.g. Terrain Intersection Curves (for integration of 3D

objects with the terrain)



ExtendingCityGML



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

ExamplesEnvironmental 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



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



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 disadvantagesNo further semantic structuring of generic objects and

attributesPossible naming conflictsLimited number of predefined attribute types:

integer, double, string, date, URI

<Building gml:id=“Building0815">



<stringAttribute name=“BuildingOwner">

<value>Mr. Smith</value>

</stringAttribute>

<doubleAttribute name=“Value">

<value>3500000.0</value>

</doubleAttribute>



<lod2Solid> ... </lod2Solid>

</Building>

Example for Generic Attributes



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 simultaneouslye.g. CityGML Building features augmented both by properties

from real estate and noise pollution simulation

Requires combinable application schemas



Example of application specific attributes

Example for a CityGML Building feature with application specific extra information (qualified by extra namespaces):

<Building>

<function>1000</function>

<lod2Solid> ... </lod2Solid>

...

<noise:immissionPoints> <gml:MultiPoint> ... </gml:MultiPoint></noise:immissionPoints>

<noise:buildingHabitants>8</noise:buildingHabitants>

<realEstate:value currency=“EUR“>400000</realEstate:value>

</Building>




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 needsADE hooks allow for augmenting the predefined CityGML featuresNo formal standardization process needed

Specification within their own XML SchemaAllows for XML validation of ADE enriched documentsEnsures semantic and syntactic interoperabilityGlobally unique XML namespace prevents naming conflictsADEs can be used simultaneously within one instance documents



CityGMLADEs


XML

NoiseSimul. Disastermanagement

ALKIS ATKIS[NAS] ...

. . .

CityGML

GML

ISO

191

xx



ADE implementations

ADE Application domain Proposed by

NoiseADE Noise pollution simulation

SIG 3D

SubsurfaceADE Underground features, e.g. tunnels

SIG 3D

CAFM-ADE Computer Aided Facility Management

TU München

HydroADE 3D flood simulation HFT 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)



Application Examples



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 toCityGML)



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)



Noise immision mapping

Noise immsion mapsreported to EU (via WMS service)

Noise immision simulation

3d geodata in CityGML as input for the calculation of noise immision maps



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 applicationsData formats: CityGML and IFC



Homeland Security

CityGML building visualised using LandExplorer from outside (left)

room-based representation of the security level (right)



http://www.opengeospatial.org/pub/www/ows4/index.html

Homeland Security



Coming to the end…



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



What is CityGML‘s Use for Research?

Base model / base ontology forgeodatabase developmentsproject specific extensions (like relations or new feature types)

Could be target model of 3D extraction methodsconcerning feature types, aggregation structures5 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 availableBerlin, Bonn, Bochum, Hamburg, Stuttgart, Recklinghausen, …also 3 freely accessible Web Feature Services delivering CityGML


Technische Universität Berlin

2009/05/19

Introduction to CityGML

Thomas H. KolbeAlexandra Stadler

Chair of Geoinformation MethodologyInstitute for Geodesy and Geoinformation ScienceBerlin University of Technology

{ kolbe | stadler }@igg.tu-berlin.de

19th of May, 2009

EduServ7 Pre-Course Seminar in Ås

department of geoinformation science technische universität berlin 2009/05/19 introduction to...

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