Urban digital twins

According to the German Institute for Standardization, urban digital twins are cross-system and cross-user group digital representations of local reality with a systematic reality comparison (DIN SPEC 91607). Science defines digital twins as digital representations of material or immaterial objects from the real world. All UDCs are connected to the real world via sensors and data streams.

Applied to the  smart city, digital twins are interactive further developments of 3D city models. UDCs combine a wide range of data to create a realistic, digital image of the city. In addition to objects such as buildings and streets, they can also depict mobility flows, greenhouse gas emissions and social interactions. In this way, they allow the current situation to be analyzed in detail or developments and measures to be simulated.

Digital twins are becoming an increasingly important method for digital and smart cities. Institutions and standardization bodies around the world, such as the German Institute for Standardization (DIN) and the International Organization for Standardization (ISO), are working on the development and use of urban digital twins. The standardization "Digital Twin for Cities and Municipalities" (DIN SPEC 91607) published in 2024 contains important impulses and guidelines for cities throughout Germany. The German Association of Cities, the federal and state administrations and the European Union are also actively promoting the development of the approach. Urban Digital Twins are thus becoming a central building block for data-supported, transparent and sustainable urban development.

The development and networking of urban digital twins (UDZ) is an important component of the  smart city strategy of the state capital Stuttgart. In practice, data from various sources is gradually added to an urban digital model of buildings, streets and entire city districts. The aim is for the digital twin to provide up-to-date information and forecasts and become the basis for decisions.

However, the digital twin cannot include all the processes that make up a complex structure such as a city - this is where the development of an accurate and up-to-date image reaches its limits. Even a high-resolution virtual 3D model that integrates traffic or energy flows in (near) real time cannot depict all social, societal or economic activities.

Since a city as a system is made up of numerous aspects, the urban digital twin is no more than a model. Therefore, not only one twin can be developed for the digital representation of a municipality: Rather, different specialist or sectoral twins will emerge in the future, which will continue to evolve. It is crucial that these functional twins are developed in a coordinated manner, have a similar structure and are based on overarching and open standards.

Every day, the city copes with an enormous and constantly growing volume of traffic. At the same time, it must maintain the population's high quality of life and keep the environmental impact associated with the volume of traffic to a minimum. With the help of the  "Digital Twin Mobility and Environment" measure funded by the federal government, the city's existing information base has been raised to a new level. The digital twin focuses on networking existing systems and databases, closing data gaps and providing data and services in line with requirements. This creates an improved basis for controlling and optimizing the city's transport and environmental systems.

The individual offices of the Stuttgart city administration have different requirements for the development of further sectoral twins. Examples include the development of a digital twin for the urban climate, for the real estate market or the Stuttgart Rosenstein urban development project. A key task here is the overarching coordination of the projects and coordination with  Smart City Stuttgart.

With the Urban Digital Twin, the state capital Stuttgart has a tool for data-supported, transparent and sustainable urban development. The quality of the decision-making basis within the administration, for the top management and the political level is improved enormously.