A digital twin for smart cities replicates the lifecycle stages of physical entities in a virtual environment, providing a model-based data monitoring, simulation, and decision support system for city operations. Digital twins in city management can assist with various tasks, including traffic and public transportation control, resource allocation, infrastructure development and planning, environment monitoring, and emergency response. As a result, the data for smart city digital twins is highly diverse, consisting of spatial-temporal data from building information models (BIM), sensor data such as radar data for traffic surveillance, and video footage. Integrating these different datasets into the data analytics of digital twins presents a significant challenge. To address this, digital twins are closely linked with the City Information Model (CIM), which acts as the fundamental framework for data integration, providing accurate and real-time urban information to the digital twins.
CIM is a city-level information management system powered by BIM, Geographic Information Systems (GIS), and the Internet of Things (IoT). It supports dynamic, real-time, and intelligent urban management through comprehensive processes of data collection, fusion, analysis, and application. CIM addresses critical aspects of data fusion from various data sources, including data acquisition, processing, modeling, visualization, and application. To enhance the efficiency and intelligence of CIM development, a data-driven CIM Development Framework has been established to address key challenges, including data governance, standardization, and integration within CIM implementation. As the foundational digital backbone of CIM, BIM is a parametric semantic modeling framework that provides detailed structural and operational insights for urban systems using object-oriented 3D digital twins. Originally developed as an architectural design innovation, BIM has evolved from supporting building-level design, construction, and operations (DCO) workflows to enabling citywide infrastructure lifecycle management. Modern BIM extends beyond geometric modeling, incorporating multidimensional data schemas that encompass material properties, structural mechanics, temporal phases, and energy performance metrics, thereby creating a data-rich foundation for urban computational analysis. Another vital enabler for CIM is GIS data, which offers a comprehensive framework for spatial analytics in urban digital twins. By integrating multiple geospatial data layers with urban operational datasets, GIS develops a spatial decision support system that enhances urban planning accuracy at sub-meter levels. GIS platforms include distributed sensor arrays, satellite remote sensing feeds, and IoT-derived real-time telemetry, supporting predictive urban analytics, such as city traffic management.
Digital twins for smart cities have been adopted in many cities worldwide. Countries like Singapore and the United States lead in smart city development and traffic management. China actively implements CIM in major cities for digital governance and urban management. Meanwhile, European nations prioritize sustainable development and disaster management. A notable example of a digital twin urban project is Xiong’an City in China, which functions as the hub for the Beijing-Tianjin-Hebei economic triangle. Xiong'an New Area was the first in the country to introduce the "Digital Twin City" concept from the outset of construction; a digital model was created for every building, and planning and building digital models for parks, green spaces, and water systems occurred simultaneously. The digital twin city is a connected digital-physical system that provides real-time monitoring through over 100,000 video terminals and nearly one million other sensing devices, covering more than 500 km of roads and over 5,000 smart buildings. The Xiong’an Urban Computing Center, along with the Integrated Data Platform, IoT Platform, Video-One-Net Platform, and the CIM (City Information Model) Platform, constitutes the core of the digital twin, utilizing AI, 5G transmission, and cloud computing for data integration, processing, analysis, and decision-making. Through the CIM platform and the spatiotemporal hub, it links the 1,770 square kilometers of the New Area's spatiotemporal data network, covering the entire city lifecycle from construction to completion.
The “smart lampposts” at city intersections are equipped with cameras, LiDAR, millimeter-wave radar, and other intelligent devices that gather, combine, and send image and radar data to a central cloud platform. This enables real-time traffic monitoring and adjustments based on traffic flow, improving overall traffic movement. During rush hour, when heavy congestion occurs in one direction, the green light at relevant intersections automatically stays on longer as traffic volume increases. When buses exit side streets, the pedestrian signal switches to red immediately to ensure pedestrian safety. The data on traffic patterns and flows also helps inform the intelligent design of public transportation to reduce congestion during peak hours.
Every building in the city has a building information model (BIM) from the beginning of its construction, covering its entire lifecycle, from construction to normal operations. The BIM provides a 3D model of the building's structure and layout and tracks resource allocations and utility usage. Sensors are also installed throughout the city's utility tunnels—including power, communications, gas, heating, water supply, drainage, and other pipelines—that transmit real-time environmental data, enabling online inspections and verification. One use of BIM is to quickly determine if an elderly person living alone has had an accident at home, with the approval of the elderly person’s relatives. The “multi-meter collection” system at the Xiong’an Urban Computing Center manages this issue. If there is a prolonged absence of water usage data, the system automatically issues a warning. It then sends a work order to the community, prompting staff to check whether the elderly person needs assistance. As technology advances, many use cases leveraging digital twin and CIM technology become possible.
City-wide digital twins transform urban management by integrating various datasets into a single, spatiotemporal model (CIM) driven by BIM, GIS, IoT, and scalable analytics. The technical framework must address semantic integration, real-time data ingestion, scalable storage and processing, and governance. Xiong’an New Area demonstrates a large-scale implementation where integrated platforms, extensive sensing, and lifecycle BIM enable improvements in traffic, utilities, and community services.
The technical details of the topic discussed here are in the paper “The Development and Construction of City Information Modeling (CIM): A Survey from Data Perspective”, and news article in Chinese.