The Hitchhiker's Guide to Fused Twins: A Review of Access to Digital Twins in situ in Smart Cities

TL;DR

This paper advances the concept of embedding the DT into the PT through Situated Analytics to form Fused Twins (FTs), which allows access to data in the location that it is generated in in an embodied context that can make the data more understandable.

Abstract

Smart Cities already surround us, and yet they are still incomprehensibly far from directly impacting everyday life. While current Smart Cities are often inaccessible, the experience of everyday citizens may be enhanced with a combination of the emerging technologies Digital Twins (DTs) and Situated Analytics. DTs represent their Physical Twin (PT) in the real world via models, simulations, (remotely) sensed data, context awareness, and interactions. However, interaction requires appropriate interfaces to address the complexity of the city. Ultimately, leveraging the potential of Smart Cities requires going beyond assembling the DT to be comprehensive and accessible. Situated Analytics allows for the anchoring of city information in its spatial context. We advance the concept of embedding the DT into the PT through Situated Analytics to form Fused Twins (FTs). This fusion allows access to data in the location that it is generated in an embodied context that can make the data more understandable. Prototypes of FTs are rapidly emerging from different domains, but Smart Cities represent the context with the most potential for FTs in the future. This paper reviews DTs, Situated Analytics, and Smart Cities as the foundations of FTs. Regarding DTs, we define five components (Physical, Data, Analytical, Virtual, and Connection environments) that we relate to several cognates (i.e., similar but different terms) from existing literature. Regarding Situated Analytics, we review the effects of user embodiment on cognition and cognitive load. Finally, we classify existing partial examples of FTs from the literature and address their construction from Augmented Reality, Geographic Information Systems, Building/City Information Models, and DTs and provide an overview of future direction

Figures (22)

• Figure S1: Comparison of a Digital Twin and Fused Twins. In both rows, the same lobby of a building is shown. a) the DT of a sensor system with 390 nodes is visualised in Virtual Reality (VR) gruebel2021feasibilitygruebel2016eve. The white areas visualise the areas of observation and the coloured sphere encode the type of sensor that is located at the respective position in the building. b) the FTs gruebel2021fused are visualised in Mixed Reality (MR) speicher2019mixed by embedding the DT in situ in its PT thus fusing the two. The fused representation enables Situated Analytics thomas2018situated that facilitates the user understanding of analysis through spatial cues of the environment.
• Figure S2: Components of a Digital Twin. A DT is often thought of as the interaction between the PT and the DT grieves2017digital, but any DT implements five core components, even if only partially. These components are the Physical Environment, the Data Environment, the Analytical Environment, the Virtual Environment, and the Connection Environment tao2017digital. The PT is measured through the Physical Environment of the DT, and the raw data is stored in the Data Environment. The Analytical Environment provides simulations, services and automatisation. Users often only perceive the DT represented in the Virtual Environment as a model of the PT without being aware of the involvement of all the other components. The Connection Environment is the invisible glue that holds the different components together and enables composition with other DTs if properly implemented. Generated with http://draw.io.
• Figure S3: The Smart City with a Digital Twin Foundation. Smart Cities rely on effective data collection, analysis, and communication to work. A DT can provide the required processing of the data collection systems to formalise the PT. In a Smart City, a DT provides analysis for governance, management, and entertainment. While governance refers to directing the city's future, management refers to the present state of the city, and entertainment refers to the use of the city. Generated with http://draw.io.
• Figure S4: Composition of Digital Twins to describe higher order complex systems. Multiple DTs are composed into higher order systems such as cities. Here an open stationary city DT is composed of different open or closed and mobile or stationary DTs such as building DTs, transportation DTs and Infrastructure DTs. Each of the DTs contains complex nested DTs of different types such as for healthcare or industrial settings. The complexity level can be arbitrarily increased through nesting. Generated with http://draw.io.
• Figure S5: Immersive Analytics compared to Situated Analytics. The real world is schematically represented in grey. AR content is shown in blue. On the left side, a user is displaying a smart city environment (blue model) in non-situated AR. Interactables are highlighted in white, and several pop-ups showing information (white squares) are opened. Immersive Analytics make use of 3D space to visualise content but can be independent of the spatial context surrounding them. On the right side, a user (in yellow) is walking through the physical environment of the smart city. In Situated Analytics, interactables are AR content that is displayed in situ of the physical environment that they describe. Similarly to a), pop-ups (blue squares) are showing content to the user in AR space. Generated with https://miro.com and https://rhino3d.com with royalty-free models from https://cgtrader.com.