Scope
This document is an OGC Encoding Standard for the representation, storage and exchange of virtual 3D city and
landscape models. CityGML is implemented as an application schema of the Geography Markup Language
version 3.1.1 (GML3).
CityGML models both complex and georeferenced 3D vector data along with the semantics associated with the
data. In contrast to other 3D vector formats, CityGML is based on a rich, general purpose information model in
addition to geometry and appearance information. For specific domain areas, CityGML also provides an extension
mechanism to enrich the data with identifiable features under preservation of semantic interoperability.
Targeted application areas explicitly include urban and landscape planning; architectural design; tourist and
leisure activities; 3D cadastres; environmental simulations; mobile telecommunications; disaster management;
homeland security; vehicle and pedestrian navigation; training simulators and mobile robotics.
CityGML is considered a source format for 3D portraying. The semantic information contained in the model can
be used in the styling process which generates computer graphics represented e.g. as KML/COLLADA or X3D
files. The appropriate OGC Portrayal Web Service for this process is the OGC Web 3D Service (W3DS). An
image-based 3D portrayal service for virtual 3D landscape and city models is provided by the OGC Web View
Service (WVS).
Features of CityGML:
Geospatial information model (ontology) for urban landscapes based on the ISO 191xx family
GML3 representation of 3D geometries, based on the ISO 19107 model
Representation of object surface characteristics (e.g. textures, materials)
Taxonomies and aggregations
o Digital Terrain Models as a combination of (including nested) triangulated irregular networks
(TINs), regular rasters, break and skeleton lines, mass points
o Sites (currently buildings, bridges, and tunnels)
o Vegetation (areas, volumes, and solitary objects with vegetation classification)
o Water bodies (volumes, surfaces)
o Transportation facilities (both graph structures and 3D surface data)
o Land use (representation of areas of the earth’s surface dedicated to a specific land use)
o City furniture
o Generic city objects and attributes
o User-definable (recursive) grouping
Multiscale model with 5 well-defined consecutive Levels of Detail (LOD):
o LOD0 – regional, landscape
o LOD1 – city, region
o LOD2 – city districts, projects
o LOD3 – architectural models (outside), landmarks
o LOD4 – architectural models (interior)
Multiple representations in different LODs simultaneously; generalisation relations between objects in
different LODs
Optional topological connections between feature (sub)geometries
Application Domain Extensions (ADE): Specific “hooks” in the CityGML schema allow to define application
specific extensions, for example for noise pollution simulation, or to augment CityGML by
properties of the new National Building Information Model Standard (NBIMS) in the U.S.