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CUPUM '09

City Models‎ > ‎Modelling process‎ > ‎

Standards

City models can be produced in a range of file types prescribed by the program in which they were created. These include AutoCAD drawing files (.dwg), 3ds Max (.max, .3ds) CityGML and ESRI’s shapefiles (.shp)... In order to ensure a sustainable virtual city model, file types and modelling software that is adopted should be interoperable with a range of software solutions. For example, most 3d modelling programs recognise Autodesk’s dwg file format and 3ds extensions. Furthermore, VRML (and VRML2.0) is now widely accepted and is an important platform for publishing 3d models over the web..

INSPIRE (Infrastructure of Spatial Data in Europe) is an EU department that aims to establish common standards and protocols for all spatial data. Ultimately, this means that spatial data, that provides the foundations for the geometry of virtual cities, can be shared across a Spatial Data Infrastructure (SDI).


See also: ISO overview

CityGML (City Geography Mark-up Language) is a standard for representing city models and is based on the standard GML3 from the Open Geospatial Consortium that  describes logical spatial and semantic modelling processes.
CityGML Level-of-detail protocols:
 LOD 0 2.5D digital terrain model, over which an aerial image or map may be draped. Positional and height accuracy ≥5m (depending on data source)
 LOD 1 As above with simple block model buildings (without roof structures, facade details or textures).

Positional and height accuracy ≥5m

Objects with a footprint of at least  6m x6m must be included.

 LOD 2 As above, including differentiated roof structures and textures. Vegetation may also be represented.

Positional accuracy ≥2m

Height accuracy ≥1m

Objects with a footprint of at least  4m x4m must be included.

 LOD 3 Architectural models with detailed wall and roof structures, balconies, bays and projections.  High-resolution textures can be mapped onto these structures as well as detailed vegetation and transportation objects.

Positional accuracy ≥0.5m

Height accuracy ≥0.5m

Objects with a footprint of at least  2m x2m must be included.

 LOD 4 As above, plus interior structures and details, such as rooms,  interior  doors, stairs and furniture.

Positional accuracy ≥0.2m

Height accuracy ≥0.2m

Subpages (1): ISO overview