Thematic module for man-made subsurface structures

[gbuehler]

Posted by: on 2010-02-25 10:45:48
Document Title: City Geography Markup Language (CityGML) Encoding Standard Version: 1.0
Proposal: Man-made subsurface structures such as tunnels, pedestrian subways, underground stations or subsurface buildings are essential urban objects which have to be adequately represented in virtual 3D city and landscape models. However, CityGML 1.0 does not provide a semantic model explictily dedicated to man-made subsurface structures. The only possibility to model and exchange subsurface objects in CityGML 1.0 is to use a GenericCityObject as proxy. Alternatively, a corresponding ADE could be defined. Both approaches face disadvantages. First, GenericCityObjects are simple in structure and are hence not suitable to replace a semantically rich model for underground objects. Second, subsurface structures are not specific to just a single application domain. Several ADEs could emerge proposing different semantic models. What is required is a common and standardized thematic module on man-made subsurface structures in CityGML.

The Special Interest Group 3D (SIG 3D, initiator of CityGML) of the national Spatial Data Infrastructure of Germany (GDI.DE) has developed a comprehensive data model for subsurface structures. It comprises a rich semantic model for underground objects such as tunnels as well as their geometric representation in four different LODs. The model is based on the CityGML 1.0 Core module and is realized as CityGML ADE. By this means, compliance to the CityGML standard is ensured and existing concepts of CityGML (e.g., appearance modelling, grouping of objects, generic extensions) can be directly applied to the subsurface features.