Representation of CityGML 3.0 Dynamizers in Web Streaming Formats for 4D Urban Digital Twins

Abstract. The integration of static 3D city models with temporal data, such as IoT sensor data, is essential for monitoring and analysing highly dynamic changes in Urban Digital Twins (UDTs). CityGML 3.0 introduces the Dynamizer module, which formalises the integration of semantic 3D city models and temporal data from various sources. However, CityGML datasets cannot be visualised directly on the web and require conversion to web streaming formats, which do not natively support temporal data integration. This research presents a methodology for transferring data structures defined in CityGML 3.0 Dynamizers into web streaming formats to enable 4D web visualisation in UDTs. We demonstrate representation strategies for various Dynamizer classes within the OGC standard 3D Tiles using structured metadata, define the required metadata for web viewers to discover and interpret Dynamizers, and outline optimisation techniques for efficient rendering of city-scale 4D scenes. A prototype 4D web viewer validates the approach, providing interactive visualisation of integrated semantic 3D models and high-resolution temporal data.