Department of Geoinformation Science
Technische Universität Berlin
1/6/2012
BIM, CityGML, and
Related Standardization
Thomas H. Kolbe
Director
Institute for Geodesy and Geoinformation Science
Berlin University of Technology
1st of June, 2012
Digital Landscape Architecture Conference 2012 in Bernburg/Dessau
2 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Overview
Motivation: 3D information integration
data integration on the visualization level
data integration on the geodata level
Standardization of 3D geodata exchange
The different modeling approaches and paradigms
Computer graphics approach
AEC / CAAD / BIM approach
GIS approach
A short look at data formats (IFC, CityGML) / comparison
3 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
City B
City Model
Level-of-Detail 1-3
City A
City Model
Level-of-Detail 1-3
Authority A (DTM)
Regional Model
Level-of-Detail 0
Company C
City Model
Level-of-Detail 3-4
Application Model
A B „Zonal
Fragmentation“ B
C
B
C C C
Application Model
„Layer
Fragmentation“
Internet /
Intranet
User
Provider
Key Issue: 3D Information Integration
4 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Different Stages of Information Integration
OGC Web
Feature Service
CityGML
OGC Web 3D
Service, WVS
VRML / X3D / KML
System A
Geodata
graphical
Elements
System B
Geodata
graphical
Elements
Geodata level
Visualization level
Web Client C
5 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Visualization Level Geodata Level
Interoperability on the geodata level requires
standardised base model and exchange format for
spatial (3D) objects e.g. ISO 191xx / GML3; ISO Step; XML
common application / information model (ontology):
consensus on terms, entities, their properties and relations, and: their meanings
conceptual schema and implementation schema
appropriate data services e.g. Web Feature Service
Interoperability on the visualization level requires
combinable graphical elements (3D geometries +
styling / appearance information) and interaction elements
standardised model and exchange format
for (3D-) graphical elements e.g. KML, X3D, VRML97, COLLADA
appropriate portrayal services e.g. W3DS, WPVS
6 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Standards are Key
for the integration / combination of (3D geo) data
from different data sources
7 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Who standardizes (geo)virtual 3D worlds?
Open Geospatial Consortium (OGC)
Exchange formats GML; CityGML; KML; Web Services: WFS, WTS, W3DS
buildingSMART Alliance (formerly called IAI)
Product model for AEC/FM: Industry Foundation Classes (IFC)
Web 3D Consortium (W3D)
Originator of VRML, GeoVRML, X3D
3D Industry Forum (3DIF)
Graphics format “Universal 3D“ (U3D) -> direct embedding in PDF
Khronos Group
Exchange format COLLADA (used within Playstation, Google Earth)
International “De Jure“ Standardisation: ISO
ISO standards of the 191xx family ( OGC Standards), X3D, IFC
8 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Standardization of 3D Geodata Exchange
Data formats
encoding of geometry, topology, appearance, and semantics
recent developments specify meta formats (e.g. GML3, COLLADA)
meta formats are only the basis or container model for the specification of user-defined application schemas
Application schemas
domain specific (semantic) modeling / ontology
result of a consensus process within an application community
are mapped to concrete data formats
examples: CityGML ( GML), IFC ( Step),
INSPIRE Data Specifications ( GML), ALKIS / ATKIS ( GML)
Data access & processing
Web Services (currently mainly by the Open Geospatial Consortium)
specific for 3D: data and visualization services (WFS & W3DS, WVS)
9 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Determining Factors on 3D Data Standards
Required or intended data characteristics / quality
details and structure of geometry, topology, semantics, and
appearance
scope and scale
Original application domain in which a standard is
being developed (AEC, GIS, Simulation, Gaming)
determines the 3D modeling paradigm; also affects the scale
Intended applications
e.g. visualization only; environmental or training simulations;
facility management, complex spatio-semantic analyses
Type of usage (stand-alone, linked to/over the web)
Type of access (filesystem based, web services)
10 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Elements of (3D) Spatial & Semantic Modeling
Geometry
Topology
Da
ta m
od
elin
g
Me
tad
ata
Appear-
ance
Semantics
• themat.
structure
„(Geo)Spatial Information Modeling“
11 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
3D
Approaches to 3D City / Landscape Modeling
Computer Graphics
Scene Graphs
Geospatial / GIS
(Semantic) City and
Landscape Models
AEC / CAAD
Building Information
Models
Computer Games /
Simulation
Simulation and
Interaction Models
12 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Computer Graphics Approach
Real world Abstraction wrt. visual characteristics 3D model
Only visible elements and properties of objects are relevant
restriction on geometry and graphical appearance
efficient visualization; modeling of graphical characteristics
scene graph models (B-Rep + primitive instancing)
typically no consideration of object semantics
13 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Computer Graphics Approach
What is modelled?
geometry (parametric primitives; boundary representation)
material / appearance
typically no semantic information; limited topology
interaction methods and object behaviour
all elements are structured within scene graphs
elements have local 3D coordinates (mostly in Euclidean CS)
aggregation using group nodes; transformation nodes
allows to define prototypes / reuse object definitions
some exchange formats support georeferencing
GeoVRML, X3D, KML, COLLADA (from V1.5), OpenFlight
but: models often are restricted to one coordinate system (type)
14 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Underneath the surface…
Computer graphics models are generated predominantly for the
„nice“ (often realistic) and efficient visualization
only visible parts are trustworthy!
Wire frame visualization
dormers are extruded
through the whole building
Textured visualization
visualization does not reveal over-lapping building and dormer bodies
15 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
AEC / CAAD Approach
Buildings Abstraction on design (plans) Real world
Mapping of the constructive elements
component oriented modeling:
Constructive Solid Geometry (CSG)
Building Information Modeling: Semantic objects with geometries
16 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
AEC / CAAD Approach
What is modelled?
geometry (parametric primitives; boundary representation;
constructive solid geometry; sweep volumes)
topology
limited material / appearance
explicit semantics within building information models (BIM)
(but not with legacy CAD formats like DXF)
Most important BIM exchange format is IFC (Industry
Foundation Classes)
IFC defines a product data model for buildings / sites (only)
Elements of a BIM dataset are aggregated within a project
BIM / CAAD models have very limited support for georeferencing
models are restricted to an Euclidean, cartesian coordinate system
17 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Geospatial / GIS Approach
Real world Topographic abstraction Surveying
generally, only the object surfaces are observable:
Boundary representation (B-Rep)
Points and surfaces are surveyed / registered using sensors
Urban Information Modeling: Semantic objects with geometries
18 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Geospatial / GIS Approach
What is modelled?
geometry (3D in ISO 19107: only boundary representation)
topology
semantic information
limited appearance / material properties
Models are based on the notion of geographic features
(according to ISO 19109); exchange format is GML
Application schemas define ontologies, i.e. taxonomies
and partonomies of feature types (using OO concepts)
Ontology for 3D city models: CityGML
always georeferenced; any 3D coordinate reference system
(CRS) can be used (and mixed within the same dataset)
all geometries must belong to a CRS; nesting is possible
19 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Differing Modeling Paradigms
Volumetric, parametric primitives
representing the structural components
of buildings
IfcWallStandardCase
IfcBeam
IfcSlabIfcWindow
BIM (e.g., IFC) Constructive Solid Geometry
Accumulation of observable surfaces of
topographic features
WallSurface
InteriorWallSurface
FloorSurface
IntBuildingInstallation
GroundSurface
Window
3D GIS (e.g., CityGML) Boundary Representation
20 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Differing Modeling Paradigms
Volumetric, parametric primitives
representing the structural components
of buildings
IfcWallStandardCase
IfcBeam
IfcSlabIfcWindow
BIM (e.g., IFC) Constructive Solid Geometry
Accumulation of observable surfaces of
topographic features
WallSurface
InteriorWallSurface
FloorSurface
IntBuildingInstallation
GroundSurface
Window
3D GIS (e.g., CityGML) Boundary Representation
Well suited to
support (generative)
design processes,
hence, to create
models for
planned objects
Well suited to
support model
generation from
surveying /
observation,
hence, to create
models for existing
objects
21 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
3D Standards / Data (Exchange) Formats
Differentiation between general purpose exchange
formats and information model standards
General purpose: X3D, VRML, U3D, COLLADA, KML, GML,
Shapefiles, DXF, OpenFlight
Information models: CityGML, IFC
Different categories / fields of origin
CG / VR / Simulation: X3D, VRML, U3D, COLLADA, OpenFlight
Geospatial / GIS / UIM: Shapefiles, KML, GML, CityGML
AEC/FM / CAAD / BIM: IFC, DXF
The expressivity of a standard limits its representation
capabilities (important wrt. prevention of information loss)
Complementary use of GIS, AEC, and CG standards!
22 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Industry Foundation Classes (IFC)
ISO standard 16739 for semantic site/building models
developed by the buildingSMART Alliance
representation of site / building models with respect to
their geometry, topology & semantics
comprehensive 2D & 3D geometry support: B-Rep, CSG, Sweep
integrates diverse crafts; incl. material & cost calculations
most used and most comprehensive data model and
exchange format for Building Information Modeling
no representation of (graphical) appearances,
simple georeferencing (starting from IFC 2.3)
exchange format is based on STEP; ifcXML is
an XML-based mapping
23 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
City Geography Markup Language – CityGML
Application independent Geospatial Information Model
for virtual 3D city and landscape models
comprises different thematic areas
(buildings, vegetation, water, terrain,
traffic, tunnels, bridges etc.)
Internat‘l Standard of the Open Geospatial Consortium
V1.0.0 adopted in 08/2008; V2.0.0 adopted in 3/2012
Data model (UML) + Exchange format (based on GML3)
CityGML represents
3D geometry, 3D topology, semantics, and appearance
in 5 discrete scales (Levels of Detail, LOD)
24 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
25 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Semantic 3D City Model of Berlin
>550,000 buildings;
• fully-automatically generated
from 2D cadastre footprints &
airborne laserscanning data.
• textures (automatically
extracted from aerial images)
• semantic information (includes
data from cadastre)
• 3D utility networks from the
energy providers
• modeled according to CityGML www.virtual-berlin.de
© NIBS 2007
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Scope of Real Property Industry IA
I-IFC
Usag
e
Space
Natural Asset
Linear Structure
Structure
Building
Facil ity / 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
Overlay
Components
Components
City
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City
GM
L
27 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
3D City/Landscape Model Exchange Formats
X3D COLLADA KML Shape CityGML IFC DXF
general purpose / information model gp gp gp gp im im gp
3D geometry + + + ++
georeferencing + + ++
appearance ++ ++ +
3D topology + +
semantics ++ ++
levels of detail + + ++
links/embedding + ++ ++ ++
extensibility + ++ + ++
fast rendering ++ ++ + + + /+ +
Legend: = basic, + = sophisticated, ++ = comprehensive; empty = not supported
1/6/2012
28 T. H. Kolbe – BIM, CityGML, and Related Standardization
Department of Geoinformation Science
1/6/2012
Summary
A range of 3D standards is available
concerning 3D data models and data exchange formats
concerning web services for data access, registry & visualization
Data standards differ significantly wrt. expressivity and
modeling paradigms geometry, topology, appearance, semantics
Facilitation depends on general application needs exchange of 3D presentations / visualization results versus
exchange of geospatial information, i.e. semantic models
CityGML and IFC model real world objects with specified
semantics (and spatial characteristics, of course) but with different scope, scales, and advantages