CityGML

The CityGML standard defines a conceptual model and exchange format for the representation, storage and exchange of virtual 3D city models. It facilitates the integration of urban geodata for a variety of applications for Smart Cities and Urban Digital Twins, including urban and landscape planning; Building Information Modeling (BIM); mobile telecommunication; disaster management; 3D cadastre; tourism; vehicle & pedestrian navigation; autonomous driving and driving assistance; facility management, and; energy, traffic and environmental simulations.

CityGML 3.0 is an evolution of the previous versions 1.0 and 2.0 of CityGML. While the previous versions standardised a GML exchange format, CityGML 3.0 standardises the underlying information model, and can be implemented in a variety of technologies including GML. The CityGML 3.0 Conceptual Model Standard describes a common semantic information model for the representation of 3D urban objects. The primary function of the model is to define the human interpretation of modelled data objects as well as their geometric representation and relationships. As such the CityGML 3.0 Conceptual Model provides a framework for integrating, storing, and exchanging 3D geospatial data.

CityGML 3.0 allows data to be encoded in GML/XML, but also in JSON or database schemas. Additional benefits compared to previous versions include much better integration with BIM, the ability to represent indoor spaces in different Levels of Detail (LOD), support for dynamic data provided by sensors and simulations, and the capability to extend the information model into Application Domain Extensions using Model Driven Architecture tools.

A GML encoding for CityGML 3.0 is available for practical use. The respective XML schema files can be downloaded from here: https://github.com/opengeospatial/CityGML-3.0Encodings/releases
A CityGML 3.0 GML Encoding specification document is under development and will be issued as a separate encoding standard in due course.

As many datasets using both CityGML 1.0 and 2.0 have been created and are in active use, these specifications will not be deprecated. However, existing data can be upgraded to CityGML 3.0.