City Digital Twin is a large interdisciplinary pilot project that aims at developing a digital twin platform for designing, testing, applying and servicing the entire lifecycle of the urban environment. This ambitious research project is simulating, for the first time in Bulgaria, the complex socioeconomic processes in the cities, to test strategies and to maximize sustainability. This requires a spatially-resolved simulation of a broad range of city specific scenarios (urban climate, transport of goods and people, infrastructure development, buildings’ energy performance, air and noise pollution, etc.). The simulation of the scenarios will be realized by building a semantically enriched, holistic, multi-layered 3D model of the city and by further developing advanced Big Data scientific methods and technologies to facilitate the simulations.

The pilot project receives a great support from Sofia Municipality, Sofia Investment Agency and Sofproect through domain knowledge, data delivery and society engagement.

The city digital twin provides a virtual 3D replica of the objects that comprise the urban fabric (terrain, buildings, streets, vegetation), enriched with semantic details to reflect domain requirements. Although it is widely adopted for visualization, its use to support large-scale numerical simulations of heat transfer, flow of air and water, dispersion of pollutants, sound propagation and electromagnetic fields, pedestrian and traffic flow, is in its early stage. Specific semantics will be developed that address city-scale simulation requirements. This may include development of new or contributions to emerging Application Domain Extensions for CityGML, meaningful integration of data from heterogeneous sources and semantical enrichment with additional data (e.g. social data) and further development of a relational (i.e. PostGIS) or a graph database (i.e. Neo4j) to store and import/export geospatial data.

The ultimate goal of the project is to go beyond digital replicas and visualizations and to explore the full potential of integration of data from all stages of urban development and thus to push the applications of urban modelling, simulation, analysis and visualization.