ISPRS-Annals ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences ISPRS-Annals ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci. 2194-9050 Copernicus Publications Göttingen, Germany 10.5194/isprs-annals-XII-4-W1-2026-161-2026 Representation of CityGML 3.0 Dynamizers in Web Streaming Formats for 4D Urban Digital Twins Gitahi Joseph 1 Kolbe Thomas H. 1 Chair of Geoinformatics, Technical University of Munich, 80333 Munich, Germany 28 09 2026 XII-4/W1-2026 161 168 Copyright: © 2026 Joseph Gitahi 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://isprs-annals.copernicus.org/articles/XII-4-W1-2026/161/2026/isprs-annals-XII-4-W1-2026-161-2026.html The full text article is available as a PDF file from https://isprs-annals.copernicus.org/articles/XII-4-W1-2026/161/2026/isprs-annals-XII-4-W1-2026-161-2026.pdf

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.