The concept of the digital twin has been with us for decades. Broadly speaking, it relates to a digital replica of the real world with sensors that add real-time information about status or condition. For cities, it has come to mean the use of a geographic information system (GIS) to provide a common real-time view of city activities across departments, including historical data and analytical capabilities to dig into complex problems.
Digital twins go beyond 3D models, allowing cities to monitor conditions, test scenarios, and predict how a system will react to changes and modifications. The twin becomes a way to see the current and planned state of a system or location, and decide how to take action or change policies to achieve desired outcomes.
BREATHING LIFE INTO DIGITAL TWINS
Often, digital twin use cases have been attempts to mirror systems in the physical and natural worlds. The examples capture space in 3D but neglect the key factors of time and human behavior.
Now that the pandemic has surfaced so many big questions, a new approach helps city leaders consider how space is used and to answer questions about people, including the equitable distribution of city services.
Cities have used a digital twin to keep public transit safe, with an informed idea of who will use it, and how to sanitize stations, buses and rail cars. When considering vaccination efforts, a twin has allowed cities to account for access to transportation AND distribution facilities, and to reach people who express reluctance toward vaccinations.
MIRRORING THE CITY IN REAL TIME
Various networks must work harmoniously to keep a city and its people mobile, healthy and safe. Smart cities use a big data approach to monitor city systems, track their operations and make educated predictions regarding the effect of future changes.
The local government in Incheon, the third largest city in the Republic of Korea, has built a digital twin around six pillars: fire response management, traffic, urban sanitation, facilities management, urban development and city revitalization.
The sanitation pillar includes a method for tracking and routing street cleaning vehicles, so that managers have a better understanding of progress at a given moment. This real-time capability is augmented by a process that gathers data to build a map of garbage and food waste disposal collected each day, so that the sanitation department can determine how best to allocate resources.
Incheon’s digital twin will soon be used to manage the most complex part of any city: the many systems of underground assets that all exist within close proximity of one another. Sewer systems, power grids, telecommunications, subways and even natural gas lines will be monitored and controlled with the digital twin.
As the Incheon example demonstrates, a major benefit of a geographic information system is that it provides a central repository of data from disparate sources. GIS is the natural meeting ground for data about location and time. By adding a spatial and temporal perspective from GIS, digital twins can truly reflect the dynamism of a city.
When events unfold in a city, managing them effectively often requires the input of multiple organizations and stakeholders. Like a handful of stones tossed into a pond, causing multiple ripple effects that collide and combine, a city’s simultaneity can be hard to fathom, process and manage. A GIS-based digital twin displays all of the ripples in apps and on dashboards with a common view that also gives each stakeholder the ability to see and query their individual and collective impacts. Together, these insights suggest strategies for navigating the intersecting waves of various events.
The digital twin becomes a multi-directional conduit of information, without the need to relay observations and updates via a radio. The twin offers a single pane of glass that provides complete situational — and therefore operational — awareness.
THE WHERE AND THE WHEN
A GIS-enabled digital twin depicts and documents the organic nature of a city — the people who inhabit it — in a way that functions much like the human thought process with its psychological associations and models of the world. Incorporating sensors and Internet of Things devices, digital twins are helping planners and officials understand their city in real time.
A digital twin can provide a snapshot of the city as it is. How is a stalled subway car affecting overcrowding in a certain station or a specific platform in that station? What are the levels of emissions during a backup on the freeway? These are the kind of questions that take on an added urgency to preserve public health in the moment and address the longer-term considerations of climate change.
As much as a digital twin can mirror a current situation, it can also predict how that situation might evolve. Planners can game various scenarios, using historic data as evidence. A city preparing for the transition to electric vehicles, for instance, can carefully determine the best location of charging stations, model likely impacts on the city’s electrical infrastructure, and measure impacts against zero-carbon goals.
In the U.S., city governments are using digital twins in a way that combines authoritative soothsaying with difficult-to-visualize calculations. Boston and Des Moines, Iowa, for example, have employed the technology to determine if planned development will impact longstanding regulations on viewsheds and shadowing.
SPATIAL DELIVERIES
Digital twins coupled with a modern geographic information system serve as a powerful example of spatial computing. The concept, as recently described by Scientific American, involves constructing “digital twins, not just of objects but of people and locations.” This kind of digital twin cannot merely replicate the real world, it can also work autonomously to affect the world it mirrors. As many cities have demonstrated, a digital twin can optimize traffic flows with such innovations as algorithm-driven signaling systems and even switching on and off LED lane markers to expand the number of lanes whether for morning or evening commutes.
Above and beyond these sophisticated functions, a digital twin powered by GIS is a way for human collaboration to flourish. With data from different sources combining to mirror the larger whole, decision-makers have access to information that might otherwise be the sole purview of another department.
As we enter a new era of awareness and preparedness, defined by a clear-eyed understanding of the problems we face, strong communication and collaboration through tools such as GIS-powered digital twins will not merely be preferable, it will be essential.
David LaShell is a strategic consultant who runs Esri’s New York City office, where he focuses on solving urban challenges in partnership with government agencies. He has over 30 years of experience applying location intelligence to some of the largest government, utility and transit agencies in the U.S. Trained as a geographer and a practitioner of geographic information systems (GIS), he now leads a team of experts applying technology, science and GIS to address some of society’s greatest challenges — social equity, poverty, sustainability, resiliency, life-safety, education, environmental quality, and effective government.
