CIM stands for “City Information Modeling,” the concept being similar to how BIM stands for “Building Information Modeling.” However, while BIM is very much alive and well in the AEC industry, that doesn’t seem to have happened with CIM — the term hasn’t really taken off. Is that because the concept of a “city information model” was flawed to begin with, or was it because we found a better term? Or is it still in use, and if so, where? These are some of the questions explored in this article.
I first talked about CIM all the way back in 2005 in an article I wrote right after Hurricane Katrina devastated New Orleans. The article was entitled, “Hurricanes and their Aftermath: How Can Technology Help?” and it asked what we could do to better plan and manage our cities to minimize, if not altogether avoid, the enormous destruction of life and property that we had just witnessed. I concluded that article by suggesting we could apply the BIM concept on a larger scale to neighborhoods and cities:
“What we also need is an extension of the BIM concept to the level of neighborhoods and cities, perhaps in the form of a "city information model" (CIM) which can capture all the critical data about a city's geographical location, topology, major roads, bridges, buildings, and so on in an intelligent format. In time, we could also find a smart way of integrating the BIM models of individual buildings within the city's CIM, so that we have a highly accurate and detailed digital replica of a city which can be subjected to sophisticated analysis and simulations. We could then predict the impact of a hurricane, earthquake, tsunami, gas leak, bioterrorist hazard, or any other kind of conceivable disaster not only on the city as a whole but on individual buildings and neighborhoods within the city as well. Just as BIM technology can help to better integrate different aspects of a building such as space, structure, mechanical systems, and so on, CIM technology could eventually help to better integrate the different structures and services within a city, allowing it to operate in a more holistic manner and deal with a disaster more effectively.”
I revisited the CIM concept again by 2016, by which it had gathered some steam, in a dedicated article, “City Information Modeling,” and shortly afterwards, I reviewed one of the few dedicated CIM platforms that had emerged by that time: Smart World by Cityzenith (Figure 1). CIM seemed poised to be the next big thing in the AEC/GIS technology industry, particularly with the rise of the “smart city” movement, which every city all over the world wanted to be.
But then, “digital twins” happened. The idea of creating a “live” digital replica of a physical object emerged from mechanical engineering (specifically from NASA for the simulation of spacecraft in 2010) and it quickly spread to other industries, including AEC/GIS (buildings, infrastructure, and cities). While the concept of BIM for buildings has continued to maintain its own, the concept of CIM for cities seems to have all but disappeared, subsumed by “urban digital twins.”
Taking some examples from AECbytes alone, in a review published in 2020 of IES’s ICL (Intelligent Communities Lifecycle) platform, IES refers to ICL as a ““digital twin” for sustainable design rather than a CIM platform. And in the 2022 feature on the DUET project, it was entirely about digital twins, with the name itself an abbreviation for “Digital Urban European Twins.” Later that year, in the Smart City Expo World Congress held in Barcelona, we saw how cities such as Madinah in Saudi Arabia were building their smart city strategies on creating “digital twins.”
So, is the concept of CIM dead? The fact that the company, Cityzenith, developer of the Smart World CIM platform that I had reviewed in 2016, folded earlier this year was not promising. Also, in my own role in the AEC technology industry, it has been some years since I came across the term CIM. For example, a few months ago when I wrote about some of the customer implementations presented at the 2023 Esri User Conference, the term that was used to describe a citywide 3D model (Figure 2) was simply “city model.” Not “digital twins,” but not CIM either.
I find that the term “city information model” is very appropriate for a city model that includes detailed information about the entities within it, similar to how a “building information model” is an appropriate term for a building model that is just more than generic 3D geometry. And just as a digital twin of a building is not the same as a BIM model of the building, in the same way, you cannot call an information-rich CIM model of a city an “urban digital twin.”
This is because a digital twin, by its very definition, is dynamic rather than static – it is supposed to stay in sync with its physical counterpart at all times. For a building or infrastructure element such as a road or a bridge, this is done by placing physical sensors on the physical element and connecting them to its BIM model. And this is what makes that BIM model a digital twin. A great example of this is the SmartBridge project in Hamburg, Germany, which I wrote about last year. The takeaway here is that you need a BIM model to begin with, as the base, before you can create a digital twin from it.
It works the same way for CIM. You need an information-rich city model – in other works, a CIM – to then bring to life by connecting it to physical sensors placed throughout the city that can reflect its state at all times. Of course, the scale of the city is so much bigger than a building, making the scope of the problem much larger in magnitude. But the fundamental concept remains the same – you have to start with a static CIM model and then augment it with physical sensors to create a real-time digital twin of the city.
Which is why the concept of CIM is still valid.
I was recently contacted by an academic, Ala Hosseinizad from the Department of Sustainable Urban Development at TU Darmstadt in Germany, doing research work in City Information Modeling, which prompted me to look anew at this topic. I found that it is still alive in academia, and to a smaller extent, in the AEC/GIS industry as well.
One of the most compelling CIM implementations I came across was the Lancaster City Information Model, a pilot project that was developed at Lancaster University in the UK to test how a CIM could be a precursor to an urban digital twin. Developed in partnership with commercial firms including Garsdale Design, Bluesky Ltd, Cyber City 3D and Esri UK, the Lancaster City Information Model is an open-source web application with 3D geometry synthesized with additional data including data from major planning applications as well as transportation, environment, health, and census data. Built on top of Esri’s CityEngine platform, the Lancaster CIM allowed architects, planners, and stakeholders to engage with the 3D urban models of the city as well as perform urban analytics such as view sheds, masterplan scenarios, and solar potentials of buildings (Figure 3). Further work on this project would involve incorporating dynamic data supplied by the city council to allow time-based studies and research on city metabolism, on the step to transitioning the system to a full urban digital twin. (For more information, see the research paper authored by Paul Cureton at https://www.frontiersin.org/articles/10.3389/fbuil.2023.1048510/full.)
Some additional work in the area of CIM that I came across includes a CIM platform being developed for the city of Nanjing, China, which is referenced in several papers and reports including: “City Information Modeling: State of the Art”; “CIM And CIM Platform Practical Use in China Review”; and “City information modelling and urban digital twins.” Nanjing is a megacity that is the capital of the Jiangsu province of China. Faced with the pressure of rapid urban development, Nanjing joined a series of city pilot initiatives in China and is now ranked as one of the leading “smart cities” in China (see the article, “Top 10 Smart Cities in China in 2023”). Nanjing has started developing a comprehensive CIM platform to serve as the foundation of its smart city initiatives. The platform consists of an infrastructure layer, a data layer, a platform service layer, and an application layer, as shown in Figure 4. While the project is still in the initial stage, some functionality such as visualization, approval of construction projects, real estate registration, and spatial analysis for the optimization of urban layout has been implemented and is available (Figure 5)
And finally, I came across the company, 51WORLD, that has developed a CIM platform called CIM PRO (Figure 6). Founded in 2015 and headquartered in Beijing, 51WORLD has also developed a sophisticated digital twin platform (Figure 7) using the underlying technology of CIM PRO. Its location in Beijing allows it to actively support the CIM initiatives that are emerging in China, and it also being used by other governments and cities around the world. In fact, its aim is to clone the entire earth to create a “digital twin world.” I hope to explore the CIM and digital twin platforms of 51WORLD in a dedicated article soon.
Just as the concept of BIM for building design and construction is crucial and cannot be replaced by digital twins, in the same way, the concept of CIM for city planning and management is important and cannot be replaced by urban digital twins. We cannot skip the step of creating a static intelligent model of an entity before we can connect sensor data to it to make it a dynamic digital twin. Making a clearer distinction between the two – CIM versus urban digital twins – would, I think, help to make the development of both technologies stronger, which would ultimately help in the main objective of developing smarter and safer cities for us to live in.
Lachmi Khemlani is founder and editor of AECbytes. She has a Ph.D. in Architecture from UC Berkeley, specializing in intelligent building modeling, and consults and writes on AEC technology. She can be reached at lachmi@aecbytes.com.
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